(Originally posted 7/25/2022)
gltaylor
Global Moderator
As indicated earlier, there is a world of good information in the publication "Shooting Holes In Wounding Theories" by Mr. Rathcoombe.
The publication is very lengthy and in considerable depth.
I have made a "Cliff Notes" version of some of the more interesting points (to me) made by Mr. Rathcoombe.
If ballistics and wounding are of interest to you, this document may save you some time.
Major points made are cross referenced to where the full explanation can be found in the main text.
Enjoy!
SHOOTING HOLES IN WOUNDING THEORIES.odt (46.98 KB)
In addition, there are some good pieces written by Dr. M. L. Fackler and Nathan Foster if you care to search.
easttennjed
Full Member
Awesome! Thank you for putting this together!
farleg
Platinum Member
Great stuff George
Haven’t read your cliff notes yet that will be my bedtime story
The hard one for people to wrap their heads around well I had trouble is putting it all together & the 3 professionals mentioned above is putting it all together
That’s where I’m simple & take note of the fur calculator the break their findings down to my world
Just wish rathcombe would have done tests with hammers
& the one thing I’ve not seen anyone mention is the different forms of bleeding that occurs from mushroom vrs hammer
One is a crush the other is a cut & no not all monos are equal on crush or cut
Just observations & thanks again GL
Cheers
gltaylor
Global Moderator
Farleg,
You're right. Unfortunately, the nearest Rathcoombe came was very limited testing of the GSC bullets (forerunner of Hammers). He also did a bit with TSXs, but they don't perform at all like Hammers since they retain their petals.
His biggest observation was that monos probably are the wave of the future due to better penetration, even with less mass.
He talks at length about the superior penetration and damage of flat meplate bullets that crush and displace tissue at 90 degrees to the path of the bullet.
Since he never had or tested Hammers, he's unaware of the tremendous damage petals do when acting as independent missles, cutting their own paths.
Flat meplate cylinders (shanks) do more damage than smoothly rounded edge mushrooms! He got that part
kneedeep
Full Member
gltaylor Thank you again for all you do to orginize this forum and put a ton of information together in one place. It's amazing the amount of work you do here.
It's unfortunate they didn't have hammers in their testing. All the more reason for you to write a book on terminal performance farleg! You better get cracking because you have a ton of pics and on game results to organize.
Haha. Get that camp fire hot and your mates around to drag all the old highlights out of you.
kneedeep
jakesch
Senior Member
I do appreciate how he approaches cavitation and dynamic pressure. I know I brought up dynamic pressure on here before and it is good to see a more formal theory with that included.
I read the spark notes and now have started on the entire thing. Love this stuff!
gltaylor
Global Moderator
Jakesh,
There's some great information, graphics and illustrations too. I like pictures! They're easy to read
gltaylor
Global Moderator
Yeah Farleg, I agree! Just,please God! get somebody to write it for you!
(Just picking, but couldn't miss the opportunity to prod you
)
meatbuck
Platinum Member
Thanks gl.
tthetinkerer
Senior Member
One other thing I noticed is that despite his breakthrough revelations, he still maintains some preconceived notions that limit his understanding of what I call reliable vs decisive kills.
Large caliber users cling to the passthrough principle because, while there may be some tracking, you can mostly assure a recovered game animal. This is mediated by deep penetrating, through and through wounding.
The smaller caliber users like varmint and predator hunters know that fragmentation and organ evisceration is where those instant, decisive kills come from. A varmint that runs off a few yards back to his den isn't looked at as the halmark of a successful varmint cartridge.
The author believes that the acclaimed .224 caliber 70gr JSP from Speer wouldn't be a good deer stopper due to limited penetration through gel, but the proof is in the tasting of the pudding: the fragmentation of the front half into the lungs and lodging of the retained half under the far side skin is enough to anchor all but the larger varieties of deer. Just ask the hunters who use it via their reviews on websites that sell the bullet. Even more successful are the 62gr and 75gr gold dots, as well as the 75gr TMK. Just don't aim at high shoulder or do any Texas heart shots...
Combining the properties of a reliable killing bullet (deep penetrating, passthrough) and a decisive killing bullet (fragmentation) gives you the newer generation of monolithics, such as the Hammer and its now discontinued spiritual predecessor the GSC HV, that outperform C&C bullets in every way save for cost and BC. There are other monos that also demonstrate this behavior down to moderate speeds, such as Cutting Edge. Others like Maker Bullets (tipped variety), Cavity Back Bullets, and Badlands Precision, intend to expand by design but in spite of their designers they still blow off petals at moderate impact speeds and above.
Others like Barnes, Hornady, and Peregrine monolithics are sticking with the old double caliber mushroom method. I think Patriot Valley Arms from range reports do something a bit different than all the others...some say they actually expand minimally and are intended to tumble...I saw some pics and the entry/exit wounds were a bit much.
kneedeep
Full Member
You have some very interesting points tinker. Thanks for sharing them.
tthetinkerer
Senior Member
Thanks. I'm just a youngster trying to contribute something to what I see are a bunch of guys with a lifetime of experience. I get a lot more from you guys than you get from me.
gltaylor
Global Moderator
Oohhh Boy! I'd hoped this would excite some extended conversation. I am constantly impressed by the breadth of knowledge here. Thank you all! Carry on!
farleg
Platinum Member
Gday fellas just having lunch here & not enough time to reply to ea but keep this discussion going as it’s so interesting
I think rathcombe is very good & if he was still doing tests he would have seen the evolution of pill design & his research potentially would have shown more insights into what’s going on & potentially finding out a shift in his data upto that stage of testing had shown
I do believe the base of what he is saying is correct just like I do Nathan foster yet these 2 guys are opposite ends of the spectrum on their thoughts in what kills better
so I’m greedy & take both these professional guys research as a really good position to look @ in finding a pill that works the best across hunting situations yes combing thoughts & take the best of both guys research of what’s happening in a critter , once we can get that part the rest is easy & for what I’ve seen hammer has got this better than anything else hands down but I know Steve is still exploring options to improve on a already great product & i for one with the help of others won’t let Steve rest on his loreals
Now on some of these “others”no need to mention names
Oh yes rest assured the poke is warmly taken & noted for which it will be given back in due time
My book ha ha yes kneedeep I take your nudge on board but I’m thinking mine is in here already & you lot are the writers lol
I think that what is more fitting & the proper book is when all the great minds have their inputs on the subjects as I’m only a very small part of the research we have found to lift the bar but one I’m glad to help where I can
Cheers
les
Senior Member
This is great stuff! Let's toss the third leg of the stool into the conversation, accuracy. Farleg is going to like this comment. Along with accuracy is also the speed we can get with light Hammer bullets. Low recoil, fast bullets lend themselves to a more accurate shot if the bullet is good. Hammer's design and manufacturing methods lead to a more accurate bullet. I'll just speak for myself, light fast bullets with low recoil are easier to shoot accurately. I must confess, I'm getting addicted to shooting the 85 grain 6.5 grain bullets at 3500+. Not much kick, and very very accurate! My mentor for hunting elk hurt his shoulder at work and could only tolerate the recoil of his 243. It was accurate. I saw him drop 4 elk in their tracks. He would only take a head shot and I never saw him miss in the 4 years I hunted with him.
kneedeep
Full Member
I have had this same discussion regarding the larger calibers. Dangerous game loads down to elk/moose loads. Recoil tolerance per individual plays the biggest role when making a decision. 100% agreed.
tthetinkerer
Senior Member
Ditto, KD.
When I was at the Fish&Wildlife managed range out in Holopaw, I was talking to a guy. He was genuinely dumbstruck about why I'd deliberately use a 223 Remington for a deer. He told me his story about the first deer he tried to harvest with some 30 cal, don't remember which exactly, but he was hit with nerves and made a gut shot. You can all tell how that ended. From there on out, he believed that anything smaller means that you could never recover a deer from a less than ideal shot.
I told him that his story illustrated that even a so-called deer cartridge can lose deer if your shot placement isn't right. It's just a matter of people finding something to blame other than the shooter. I also mentioned that you'll always shoot a lower recoiling cartridge better than a higher recoiling one. Period. How precise they are depends on the loading and the gun, though.
farleg
Platinum Member
Gday
Les , KD & tinkerer I agree 100%
=Triangle
The greatest thing we can do is no our limits & practice will show our limits pretty quickly then practice past our limits to move the bar
Caliber / range it’s all the same = practice
Cheers
jakesch
Senior Member
One thing I want to add that I read that I do not remember seeing in the notes: Cavitation is a function of bullet diameter, shape, construction, forward and rotational velocity.
I want to put the emphasis on rotational velocity, because we all now know faster twist rates produce better results and penetration...well per the author that is due to an increased ability to generate cavitation.
Higher rotational velocity increases static pressure on sides of bullet. This would also increase permanent would cavity.
gltaylor
Global Moderator
jakesh,
Thanks. I bet that's not all I missed. Please save me the trouble and provide the reference. I'll edit the original and re-post.
All of you - if something really piques your interest, please do the same.
The reference is for the benefit of ALL!
(Oh, and increased stability factor is now so important to me the last 2 barrels I got have Much faster twists.)
farleg
Platinum Member
Gday GL
pictures
X2 on stability & we still have yet to get slippage with hammers with some pretty quick twists
jakesch im sure your going to pull a lot more for us simple minds thanks for the addition
cheers
lou270
New Member
This is a good page but the guy is fundamentally wrong on several points. Probably the main one is that temporary cavity is not important to hunting. He is obviously a big / medium bore aficiando and though he has a lot of correct data he points you in that direction with half truths.
The temporary cavity is enormously important for high velocity cartidges. If it wasn’t we would all be hunting Elk with our carry handgun that often has unexpanded bullets let alone expanded bullets the same or larger diameter as our popular 24-30 cal rifle cartridges fully expanded
The temporary cavity though “temporary” in duration has a significant impact on wounding in high (2000fps+) impacts. Tissue is elastic but it is not unlimited. In a typical rifle wound the temporary cavity will expand many times bullet diameter and then shrink back to a size somewhere between bullet diameter and max temporary cavity for the permanent cavity. ultimately the permanent cavity settling to bullet diameter as velocity slows then a bit less than diameter as the bullet pushes through vs crushing during penetration. Outside of this “hole” in the area damaged by temp cavity there is a zone where tissue is damaged but not necessarily torn. In this region there is free bleeding damage to blood vessels. Outside of this there is tissue that is stretched but undamaged. The volume of the temporary wound cavity is proprtional to the energy and the diameter to the area and velocity squared (drag)
The temporary cavity forms after the bullet passes. Any fragmentation (ala hammer petals) weaken the tissue so the stresses from the temporary cavity then rip these apart which may only stretch without damage from fragments - greatly increasing the magnutude of the permanent wound
All of the above is clearly documented some of the literature mentioned (Fackler) for ex. There is a theme in ballistic wounding related to hand guns that penetration is only thing to worry about. This is true, because there is not much energy there so penetration is limited and there is no permanent wounding from temporary cavity because velocity is too low. This is also true for hunting very large game where you need all the penetration you can get because though something like a 458 is big compared to a deer it is a spitball compared to an elephant. For vast majority of hunting you have more than enough energy for sufficient penetration and cavitation adds signifantly to wounding.
I “think” this guy is extra skewed by Fackler’s work. Fackler seemed like he was on a mission to de-emphasize the temporary cavity. If you understand his work this is because at the time (70s ish) there was a big push that energy is the main reason to select a cartidge and that the entire temporary cavity (which can be very large) causes wounding. The media got on this and Fackler stated that Surgeons would remove tissue from the entire area of a high velocity wound impacted by the temporary cavity vs. just removing what was damaged. Also around that time there was a push to declare the 5.56 as cruel due to the large temporary cavity. Fackler was on a panel to contradict this
In any case; like anything on the internet take that site with a grain of salt. Lot of good stuff but also misleading conclusions.
Lou
PS. Looks like tthetinkerer thought about the same thing. I read his post after mine so sorry if redundant
lou270
New Member
ne of the wounding literature states cavitation is a function of rotational tvelocity. In fact, they state rotational velocity has little to no impact to wounding due to having very small energy (less than 2% of total KE). Cavitation is proportional to the drag on the bullet and vast majority of this is on the front not the side except possibly on “petaled bullets”
I don’t think that “petal” type bullets were thought of in this light. By petal I mean barnes x and not hammer type where they fly off. In a “normal” mushroom you do not have the spaces between the petals so a more uniform area is pushing stuff aside. In the petal bullet there are gaps between petals. Those cause the nice swirlies we see in ballistic gel and are there because the material is flowing off the tips of the petals. The bullet is actually displacing less material (ie less wounding) comparer to a “mushroom” which is why these bullet types penetrate more. Otherwise the spinning is there in all bullets but do not notice is in gel since material is getting pushed away uniformly. Spinning faster may make it look like the bullet is doing more but it is still contacting the same amount of material ( ie the bullet frontal area is not growing) across the same distance
That being said for petal bullets the sides of the petals are contacting material. So that small amount of KE may come in to play there. I don’t think it would on a bullet that does not have petals
Anyway that is my take on it
Lou
lou270
New Member
If you think I am full of it, all of this info is in:
Bullet Penetration by Duncan Macpherson
And
Wound Ballistics by Kneubeuhl
I may be full of it, but I try and base it on research
Lou
kneedeep
Full Member
Lou
Thanks for taking time to post all of your points. I always love to see the reference material added with some common sense thoughts. It is a great conversation.
kneedeep
gltaylor
Global Moderator
Good!
Once again we have additional references and healthy discussion. I am constantly amazed at what many very smart people glean from the same studies.
Only problem is, now I've got more to
read
.
Thank you all!
Seems like all the "gurus" can do is agree to disagree?
farleg
Platinum Member
Gday
Lou & or others cavitation is the one I’d like to delve a little more into
I do think it’s underrated just not smart enough to put on paper my thoughts especially @ the moment as I’m about brain dead lol
Could you give a little more thought on how as we increase velocity the cavitation increases by how much ( I note the 2000+ velocity so what’s it like @2500 then 3000 & so on ) & do you think one of the reasons hammers make the animal bleed out more ( they just drain the blood out of the animal way more than any other brand )
Just ticking not baiting
Cheers
tthetinkerer
Senior Member
Very good take, and I'm glad you figured out why petal type expansion penetrates deeper than mushroom style...
...but the only thing I will correct is the idea that the rotation has no difference in tissue contacted with petal type expansion. It does. Think of the reverse, which is what we do with barrel fluting. Which removes more material: straight flutes, 1-12" flutes, or 1-8" flutes? The faster the twist, the more material that is contacted and stripped.
Like you note, rotational energy is small and generally plays little to no role in the permanent cavity...unless you use sharp edged, petal type expansion. Hunting with broadheads show us that not much energy is needed when you use a more efficient wounding method, i.e. cutting with a sharp edge, versus brute forcing your way through.
We agree totally that like just about all of us, the author has a bias one way or the other (in his case, in favor of big bores). I just spoke to an older hunter on YouTube about the 100+ deer he's taken without a single failure using the 223 Remington and...the 55gr VMAX. That would definitely send the author of this wounding theory into a fit, but I know how powerful the temporary cavity is so I don't doubt it!
cbjr
Senior Member
Just because I had to know...
Based on a 30-06 as an example:
After using various online calculators, a 150gr bullet in a 10twist @ 3000fps, rotational energy is 14.025 lf-lbs, which is less than 1/2% of forward energy. 14 isn't nothing, but very small in relation to forward energy.
Side note: the answer took longer to achieve than I had planned. Lol
tthetinkerer
Senior Member
You'd be surprised how little ft*lbs are involved in a stab wound or a cut with a knife. Again, I think if we're dealing with sharp petals, the energy doesn't need to be big especially when the temporary cavity is already stretching the surrounding tissues to their elastic limits.
pubmed.ncbi.nlm.nih.gov/27503509/
According to this study, it only takes between 11 and 16 joules (8.1 to 11.8 ft*lbs) to completely stab pig ribs with a Swiss army knife.
farleg
Platinum Member
Aug 26, 2022 at 7:21pm tthetinkerer likes thisQuoteEditlikePost OptionsPost by farleg on Aug 26, 2022 at 7:21pm
tthetinkerer Avatar
Aug 26, 2022 at 6:40pm tthetinkerer said:
cbjr Avatar
Aug 26, 2022 at 5:35pm cbjr said:
Just because I had to know...
Based on a 30-06 as an example:
After using various online calculators, a 150gr bullet in a 10twist @ 3000fps, rotational energy is 14.025 lf-lbs, which is less than 1/2% of forward energy. 14 isn't nothing, but very small in relation to forward energy.
Side note: the answer took longer to achieve than I had planned. Lol
You'd be surprised how little ft*lbs are involved in a stab wound or a cut with a knife. Again, I think if we're dealing with sharp petals, the energy doesn't need to be big especially when the temporary cavity is already stretching the surrounding tissues to their elastic limits.
pubmed.ncbi.nlm.nih.gov/27503509/
According to this study, it only takes between 11 and 16 joules (8.1 to 11.8 ft*lbs) to completely stab pig ribs with a Swiss army knife.
G'day fellas
Nice info
Now what happens @4k to those figures & the stretch & cut by petals is very correct & not understood well in my world
Now also why is the hide parting from flesh that no other pill design I've ever seen accomplish ( only on certain critters) &also here's a bit of info to work out why the difference
375 cal
137sh @3800 in 12 &7 twists ( various range impacts ) the 7 twist is superior on the critters I've shot not that there is shabby but a difference none the less
A Simple mind like me visualise it in a outboard motor prop the way you just cruise along vrs a full throttle & you just look how much water is displaced
Cheers
tthetinkerer
Senior Member
Yep, farleg is right. In the varmint calibers, hunters have noticed for a long time that bullets with faster twists just "splattered" critters better for some reason, and they couldn't understand why exactly.
What I think many of us don't consider is that it requires kinetic energy to deform a bullet into its final, terminal form (initially, that KE is donated in the form of velocity). Higher twists impart a state upon the bullet that allows it to reach its terminal state easier...kinda like how an enzyme lowers activation energy and allows reactions to happen faster or with less energy than otherwise. The reason for this is the additional stress that high RPMs place on a bullet.
KE translates into deformation via contact with another object (i.e. impact), and faster twists lower this threshold somewhat. The effect is more dramatic in lead core bullets.
farleg
Platinum Member
The splat word now where talking it’s gone into hiding for a while
the transfer of this energy is the one that’s the hard part to get correct/ consistent over the wide ranges of velocities / calibers
Woh just hold up a bit I seem to be warming to all this energy talk
it’s all good I think as I don’t mind saying or using it when it’s put in context like you guys can do
cheers
lou270
New Member
There are not a lot of satisfying, or concrete, answers on ballistic wounding. Seems the majority of study focuses on handgun and most rifle is based on military/fmj
As for temporary cavity (TC) a few rules of thumb from books I have:
Total TC volume is proportional to KE and density of tissue
Diameter of TC is proportional to KE transfered to target at that point in time
Assuming same sectional density, diamater of the temporary cavity is proportional to velocity
Assuming same energy, temporary cavity will be wider and shallower as sectional density decreases and longer and narrower as sectional density increases
The stress from temporary cavity only damages tissue when exceeds the elasticity of the tissue. Some tissues like muscle and lung are more elastic and some tissues are less elastic like heart and liver
Handguns and other low velocity rounds generally do not have enough energy for stretch from temporary cavity to cause permanent damage
I have not seen solid numbers but few sources say somewhere between 1500-2000 fps is where damage from stretch cavity starts to happen. I also read somewhere there is an increase at around 26-2900 fps but don’t remember where
Lou
gltaylor
Global Moderator
Lou,
Well said and concise points! Based upon my limited testing, I'd have to agree with every point from what I've seen.
Tinkerer,
You too are right on point.
I can't explain the science or technical part - but I can promise you that moderate to light bullets at very high RPM (fast twist) and higher velocity is devastating to tissue.
Speaking of elasticity - I was dumbfounded at how much the paunch/stomach could stretch and capture the "energy bubble", velocity and penetration ability of my fast bullets. It's like a huge catcher's mitt!
cbjr
Senior Member
tthetinkerer pretty interesting on the stab energy!
farleg
.375 137gr 3800fps
1:12 - 21.163 ft-lb (228k rpm)
1:7 - 62.2 ft-lb (390k rpm)
tthetinkerer
Senior Member
Lou270,
The reason you've read different numbers on the minimum velocity for temporary stretch cavity damage is because it's different for different weight and diameter bullets. Think about it:
1) velocity is a greater contributor to kinetic energy with a lighter bullet than with a heavier one, given the same total KE
2) a wider diameter bullet expends its energy more rapidly than a narrower one, given the same total weight.
That higher velocity threshold likely applies to the smaller caliber with their lighter bullets. The lower number likely applies to lighter constructed, big bore legacy cartridges.
---
Gltaylor,
Yes, smooth muscle tissue in the abdomen has a much, much greater elastic limit than cardiac or skeletal muscle tissues. I'm pretty much certain at this point that a hard quartering away shot is a no go with my 22 caliber on deer sized creatures.
harperc
Global Moderator
The splat word now where talking it’s gone into hiding for a while
In deference to the addition of better educated folks in the conversation!
harperc
Global Moderator
Good post! A&P being at the very least as complicated as terminal ballistics. Conversations combining both=lions and tigers and bears OH MY!
gltaylor
Global Moderator
Tinkerer,
I'm with you. Based upon what I've seen, I'd keep my very fast light bullets to broadside or slight quartering if i want full penetration. If you just want to capture a shank for study, hope you've got a metal detector (I used mine to find my recent shank). It's very messy and you'll have to hunt your shank in the junk. My 103PH shank made it through the paunch/guts and into the off front shoulder. It was easy to find the shank with the metal detector and cut it out. Gutting and washing the deer was messy
. Total penetration was 17". BUT I CAUGHT A SHANK!
gltaylor
Global Moderator
Oh, and Harper, you crack me up. I laughed out loud!
Thank you my friend
lou270
New Member
tthetinkerer said:
....but the only thing I will correct is the idea that the rotation has no difference in tissue contacted with petal type expansion. It does. Think of the reverse, which is what we do with barrel fluting. Which removes more material: straight flutes, 1-12" flutes, or 1-8" flutes? The faster the twist, the more material that is contacted and stripped.
Yes - this makes sense for petaled bullets. I personally dont think it is a big impact since the bullet is travelling forward at high velocity but it is there. Of course you would decrease the penetration some, but these bullets generally have more than enough to begin with
Similarly on fragmenting (ala varmint) there is more centrifugal force to whip these fragments off in a shorter distance. Why more pop on small targets
One myth I do see repeated is that faster twist keeps bullets on straight line in tissue. A pointed bullet will yaw in flesh no matter
the twist we impose. At absolute best you delay the yaw a small amount by having more twist. Bullets become more stable the farther they go so in case of a fmj you may see it penetrate an inch or so more before it starts to flip but that is it. What keeps bullets stable in flesh is shoulder stabilization. This happens when hunting bullets expand and have a larger front. The forces pushing on the outside edges (shoulder) are greater than forces trying to over turn it so keeps it going straight. Wadcatters for ex are a very stable bullet for straight penetration. Of course the bullet can hit something inside or expand irregularly that causes it to flip but shoulder stabilization is what keeps it “point forward” not spin once inside tissue. This is because tissue is many times more dense than air so the geometric stabilization imposed by spin is not a blip of what it needs to be in flesh. Best you can do is keep as stable as possible on entry but this sort of comes for free as noted bullets get more stable the further they travel
Lou
farleg
Platinum Member
Gday Lou. Like This...
Also are you saying a 12 twist vrs 7 in 375 cal will penertrate the same & in 30 cal a 11 ,10&9 twist will also penertrate the same all with the same bullet & same critters but I do note it’s hard to get consistent resistances due to subtle to major angles & what the pill plows through on its final resting place if it dosent exit
?
I’ll be straight with you& not bait as myintent is to hopefully find a reason what’s going on as I just don’t know & I’ve found these discussions enlightening & I won’t take offence just trying to put the puzzle together a little more
my terminal results are showing differences & the wound channel is staying wider for longer
now is this potentially from the bubble created @ impact & giving the shank a free ride or getting vacuumed along
this is with shedding type pills not only hammers solids show a little different traits
Cheers
ps I don’t personally like editing for myself so if I’m miss reading what you’ve put up Lou please set me straight & get me on the correct path Once again no offence will be taken
cheers
tthetinkerer
Senior Member
I will agree with you that it's the frontal geometry that keeps a bullet straight after expansion and not really twist...but twist is responsible for the transitional stabilization you need before full stabilization can occur.
With many hunting style bullets (soft points and ballistic tips) expansion or the beginnings of it are initated at the very point of contact--they begin to form a progressively more stable complex the moment they touch game. Really wide hollow points are the same. Each of these three expands primarily by way of friction.
Your sleeker BTHPs or OTMs will need hydraulic pressure to open, where friction can later take over. It needs to enter game a certain distance and pressure needs to build before any semblance of expansion can happen, though. This is where you need enough twist to stay stable.
Also, odd angles, inconsistent and uneven tissue densities can throw a bullet of course. Extra twist can help mitigate this. Some bullet types are more susceptible to this issue as well i.e. hammers, tsx, bergers, etc. while some are not i.e. VMAX, gamekings, gold dots, TNT hollow points.
gltaylor
Global Moderator
OK, you smart guys have just about outrun my headlights...
I'm trying to stay focused on Hammers and how they perform/act on impact and afterwards.
Upon impact, they shed their petals and basically become wadcutters in shape. There should not be any petals left in tact on the shank in ideal conditions. The petals become additional missles - but that's another subject.
In the process of shedding petals, a great deal of energy is used to form a very large (hopefully) and deep "bubble" (temporary wound cavity) as the shank travels forward through tissue-bone, etc.
We're not concerned with pointed bullets (fmj) or those that form mushrooms - because Hammers don't do this.
(I'm not being argumentative or trying to be offensive. Just trying to sort through all this info to learn and gain understanding)
Several of us do autopsies on animals to learn about Hammer bullet behavior after impact at different speeds, angles and bullet weights. We think we've learned that higher stability factor (rpms) translates into straighter penetration paths. It also seems that more highly stabilized bullets are less affected by impacts involving bone?
Dangerous game hunters have followed this logic for many years. They demand straight penetrations measured in Feet, rather than inches!
So anyway, that's my 2c worth. Just trying to get myself grounded so I can try to keep up with you guys
lou270
New Member
Farleg - yep, that looks like it on shoulder stabilization. As for twist vs. penetration I think it depends. These are loose rules, but for a given amount of KE if for the bullet you are using the twist increases the diameter of the wounding it will most likely reduce penetration. In that sense it is having the effect as more frontal area.
Here is probably the best ex i can find of what I am trying to say on twist vs terminal perf. This is from the new super fast twist 1/3 8.6 round. You can see that doing a 3x increase in twist caused what looks like a wider wound to start and shallower as it goes along. I think this is because of what me and tthetinkerer talked about - the faster twist allowed more tissue contact for the petals (these are petaled / mono bullets) so got more radial damage but this means bullet slows down more as it travels due to higher drag. I still dont think you will see any or much difference in a front that does not have petals whether it is the hammer stub or a typical rounded mushroom.
If you are seeing the wound stay wider for longer with hammers with faster twist where petals come off, the best guess I have is that when they come off the faster twist flings them a little further away from the base. So, as the temporary cavity forms behind the base as it is going through there is ruptured tissue further away that is weakened so as the stretch cavity reaches this it detaches things further away so the permanent cavity is larger. Pure speculation on my part though. You would also need to be shooting a round with lot of energy and velocity to take advantage of this I would think. It may actually hurt 'less powerful' rounds if their stretch cavity does not reach what the petals are damaging.
Lou
lou270
New Member
Your sleeker BTHPs or OTMs will need hydraulic pressure to open, where friction can later take over. It needs to enter game a certain distance and pressure needs to build before any semblance of expansion can happen, though. This is where you need enough twist to stay stable.
tthetinkerer
The reason these bullets come apart is because they start to yaw and present more area. This is exactly what happens with the m16 round, which is perhaps, the most studied high velocity bullet of all time. In the case of the m16 round it splits at the cannelure generally. Stagnation pressure is proportional to velocity squared so it actually goes down as the bullet penetrates. However as stability goes up, such as at greater distances, the bullet starts to tumble later since it enters more stable
Here is from book Wound Ballistics:
I expect this is how things like berger vld behave as well and why their hunting bullets have thinner jackets than their target bullets. There is no lead or hollow point to initiate expansion so a thin jacket ruptures as more force is applied to it when starts to yaw.
harperc
Global Moderator
I'm going back to bed and will try later.
lou270
New Member
If you think about it, hammers will behave exactly like a barnes X type bullet until the petals shed. By that I mean it will expand to a wide frontal area and then the petals will break off and go their own direction causing additional wound tracks. This period of 'wide' is what will cause the biggest 'bubble'. The base and the petals will keep going and the temporary cavity that formed behind the 'wide' and now 'narrow' base will tear things up beyond the crush cavity until the bullet slows down during penetration. Tissue already weakened by the petals will likely tear so long as they are not so far away from the main wound track that there is not enough stress from temporary cavity to do so.
There is nothing different about a hammer than a fmj or mushroom bullet. All the forces acting are the same. I figured the comment on twist not affecting penetration would raise some hackles but think about it. You need a sg=1.0 to be stable, meaning you are keeping the bullet point forward basically. sg 1.0 in air is like .001 or .0001 in flesh. I don't know the value but the point is the small differences in twist we are playing with - 1 in 7 to 1 in 10 is not going to change the stability in a much more dense medium significantly. For DG it could be that since they are dealing with such short distances and increase in twist causes a better angle of incidence at impact keeping things more straight. As noted you get this naturally during hunting as rotational velocity decreases much slower than forward velocity, but for DG you are not dealing with distance.
Any case, food for thought. I'm still learning on this topic and the more you read on this stuff the more questions you tend to have
lou270
New Member
Here is video on shoulder stabilization:
tthetinkerer
Senior Member
Lou270,
A boat tail hollow point will yaw if it doesn't expand, but that isn't the intended terminal effect...it's to expand, hence the hollow point part. Maybe not "match" bullets, but hollow points in general.
I think you may be arguing against yourself, here. Shoulder stabilization does take over as the stabilizing factor in tissue, but a sufficiently fast twist keeps the bullet straight long enough to expand the shoulders out. Oh, and SG of 1.0 is NOT fully stable. It pitch/yaws as it comes out of the bore. It's only stable enough that it can overcome the drag forces and can "settle down" a ways downrange.
The two clear gel shots with the 8.6BO show just what I was trying to tell you. A faster twist will place more forces against the bullet to come apart/deform, allow it to happen easier, so shoulder stabilization happens sooner.
We actually agree, you just don't know it
lou270
New Member
Not really in agreement but I will state my case A bullet expands because the pressure on it exceeds the strength of the material. At this point the bullet effectively starts behaving like a fluid and deforms until the force is less than that holding it together. This is caused by the stagnation pressure in a fluid like material and is proportional to velocity squared. Otherwise it is “harder” the faster the bullet impacts it. For ex you shoot a steel plate at 1500 fps and your bullet blows up. You shoot a deer at 1500 fps it will not expand. You shoot a deer at 2500 fps it expnds nicely. You shoot a deer at 3500 fps the bullet may shatter like hitting steel. Twist has very little to do with it. However for any fragments eroding off they may get zinged off faster/sooner with faster twist
For a typical lead / copprt bullet or hollow point designed to expand (not match type) the expansion happens immediately and is done in the first 1-2” of penetration. By this time the bullet is fully expanded to terminal shape. The lead tipped bullet gets the pressure at the tip, for the hollow point it fills and the pressure pushes outward. So there is no “stabilizing” in flesh needed assuming bullet is point forward. You could have a situation with a small hollowpoint where the angle at impact will keep fluids from entering the cavity before the bullet yaws but very unlikely to see this behaviuour with a lead soft point or decently wide hollow point. So faster twist may help here but by the time a bullet travels a little way down range (goes to sleep) shouldn’t matter. This is probably why the HH have pretty conservative twist recommendations. They have a pretty small hollow point and will be imporant to keep point on as square as possible. But just because it helps here does not mean it helps everywhere in terms of expansion nor does it mean there is anything wrong with the design. Just need to keep it in mind and probably why people sometimes report problems with the original barnes tsx and expansion.
As we discussed already for a petaled bullet the twist can help cause a wider wound because it is helping contact more tissue over a shorter distance. The forward velocity is what is causing the damage. You would not likely see this in a uniform front bullet since bullet presentation to the material is not changing. You can see that in the 8.6 pic. It has a wider wound to start but the slower twist has a wider wound towards the end. You just spend more energy up front but wound volume ends up about same just different shape. Anyway that was what I was trying to show with that pic.
Lou
farleg
Platinum Member
Gday I was up 3hrs ago & went back to bed also Carl
Now I’m back up cows are a happy & im in nunaland cause I’m stuck for words but rest assured I’m a ticking thanks heaps guys just trying to place what I’ve seen to what has been put up
So this is it for now
No hackles up here
Just seen the second use of the word “ stub “ definitely seeing I’ve lived a sheltered life
Trying to decipher why it’s applicable to DG & not your everyday deer shooter
Puts another side to the petal/shank ratio
Hydraulic & friction
Lots of big words that I have to look up the meanings of
Yep time for some work & tick some more
Thanks guys you have made my day more interestingin a nice way I’m not being smart just thankful how it’s a good conversation without the usual crap that comes up on other forums
This is the best place
Cheers
tthetinkerer
Senior Member
Lou, it seems like you're having trouble seeing the forest from the tree right in front of you. The statement that "twist has very little to do with it" is, to put it bluntly, false.
RPMs (a function of both velocity and barrel twist) place significant stress on bullets radially and this compromises their mechanical properties. Some bullets (such as Hornady's SPSX or Sierra's Blitz lines) can have so much force placed on them by the RPMs alone that they start to come apart from drag forces alone!
The reality is that people much smarter than all of us have already explained that there is a difference between the stability needed to punch paper and the stability needed to keep a projectile straight long enough to expand after impact with an animal. All the bullet manufacturers, ballisticians, and people like Litz are not all lying.
Furthermore, hunters in the South African and Australian brush figured out long ago that a faster twists keep their big game projectiles on track to hit the vitals better.
Both of these things had to do with something I talked about earlier: the transitional zone between external and terminal ballistics. That's where the twist matters most for stability on game.
lou270
New Member
Thetinkerer
I am still looking for an expert to say where twist has an impact on terminal performance. I am not trying to be contrary just stating what I have found. None of the experts who study this stuff, perform surgery on it, do experiments, perform autopsys, etc. that I have found give any credence to twist contributing to terminal ballistics. The only place I see people claiming twist has a big impact on terminal performance are on forums like this one
Below is an example and and you will find similar from “the experts”:
Rotational energy in the bullet has sometimes been proposed as a potential WTI mechanism, but this energy is too small to be important. The kinetic energy of rotation is always less than 2% of the translational kinetic energy (1/ 2mV2) even with a fast rifling twist, and is considerably lower for most bullets. This rotational”
kinetic energy is usually not included in conventional ballistics tables, and properly so, as it is too small to have any dynamic significance other than to provide gyroscopic stability to the bullet in air.”
— Bullet Penetration: Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma by Duncan MacPherson
a.co/9zUJ017
I would very much like to see a quote or paper from Litz that addresses this for ex so if you have one I would love to see it and learn from it. However I am not too interested in anecdotal evidence. I have my own on that and am trying to not let it interfere with research I have done
As for varmint bullets blowing up this is at least partially if not
mostly caused by increased structural strain and friction to the jacket as it travels through the bore at high velocity in faster twists than the bullet was designed for.
Lou
lou270
New Membe
I will also add that the only place I see what I would describe as the transition zone you are referring to is in the penetration of fmj spitzer bullets. The bullets have a narrow initial wound track called the narrow channel. However the bullets start to yaw as soon as they enter flesh. This yawing builds on itself and the bullet eventually starts to turn over. If the bullet comes apart you get a big wound at this point, if not it is a significant wound (like an expanded bullet because more area is in contact), then it completes the flip and travels base first.
The stability in air can impact the narrow channel length as the greater the angle of incidence (nose angle) at impact the more quickly the bullet starts to yaw. So the more stable the longer the narrow channel part of wound. There is no “narrow channel” in an expanding bullet track as noted because expansion starts right away where dynamic pressures are highest not later after velocity slows down
I will look around some to see if I can find any influence to twist (ie stability) referencing bullet expansion as may have missed something.
Lou
lou270
New Member
Seems split on petal vs no petal bullets. Lol:
www.americanhunter.org/content/does-a-barrel-s-twist-rate-affect-bullet-expansion/
Lou
farleg
Platinum Member
Lou
Gday Lou
the fur calculator is all they need lol
interesting points from you & tthetinkerer
siting on the sidelines watching & ticking
cheers
gltaylor
Global Moderator
Lou and tinkerer,
Well past my headlights now. Just gonna step aside and enjoy reading. Maybe something will click. The "experts" can't even agree. What do I know?
Carry on. It's great dialogue
harperc
Global Moderator
I'm enjoying this conversation immensely Lou and tinkerer. Kind of like a dog watching it's owners talk, I catch a word now and then.
It's definitely the deep end of the pool for me, but I'm paddling.
I've been a proponent of faster twist for multiple decades, and can't say my mind is fully open, but I'm trying.
Thanks guys, I'll keep checking in.
lou270
New Member
I have been enjoying discussion as well. I have been exploring / researching the literature lately so nice to share it somewhere and have a rational chat with interested folks and get few differing ways to look at things
Lou
tthetinkerer
Senior Member
Lou270,
Couple things to clear up with you. I never said that twist rate plays "a big role" in terminal ballistics. As long as the bullet is fully stable (roughly 1.5 SG or higher) or marginally stable and fired at a target at a distance far enough for the bullet to "settle down" it's being twisted fast enough. On the other hand, some bullet types (soft points, especially so-called semi points) are less prone to veering off course at impact due to how they expand and/or their geometry. If you've read enough about gyroscopic stability, you should understand that the models are just that--models. They are based on a lead core, boat tail spitzer bullet. Not a stubby little flat based cast lead bullet, or a very long VLD style monolithic bullet. What may read as a 1.5 SG may actually be higher, or it may be lower...in those cases it pays to have some extra twist to assure you have proper stability.
Second, this transitional area I'm talking about, and I'm not sure how you haven't figured out what I mean yet, is the place where the bullet transitions from external ballistics to terminal ballistics...it happens when the bullet hits the animal! (Marginally) stable bullets can easily veer off course here, or begin to tumble instead of begin to expand. What you thought I was talking about concerning penetration is actually called the neck, and any bullet's penetration path can have a neck, not just FMJ types.
Read pages 9-10 of the attached. Pay close attention. Read between the lines and use you own deductive reasoning. The role of twist rate in terminal ballistics is outlined. If a bullet is not fully stable, it still has significant nutations that affect the angle of attack. The AoA has a significant effect on what happens when it enters the animal. Hollow points may just fold over and not expand if they don't hit square. Sufficient twist helps to assure that it does hit squarely and it stays that way until it can enter into the tissue enough and form a shoulder/mushroom. Soft points are the most stable in this regard, as they don't need to enter the animal to form shoulders...it begins the moment they contact the animal.
You seem smart enough not to need an "expert" to tell you those things in plain English, but rather should be capable of deducing it from the examples they're giving you a long with all the understanding you've obtained from internal, external, and terminal ballistics, along with knowledge about stability and material properties. The amount of research you appear to have been doing may be lost upon people who believe in assuring suffient twist rates on game on "these kinds of forums."
Attachments:
Terminal_Ballistic_Performance-1.pdf (973.54 KB)
tthetinkerer
Senior Member
I just read the article and it's full of holes. My God, seriously...?
First, what kind of bullet was Nosler using? Was it hollow point spitzer? A dum dum? A ballistic tip? Lead core or monolithic? What was the target distance? I can assure you, a hunting bullet from a zero twist barrel will not expand the same as a twisted on unless it's at point blank range and it's a soft point.
Barnes demonstrated exactly what was originally proposed in this thread, and EXACTLY what I was saying about faster twist with sharp petals on a monolithic cutting more tissue as it creates a wound channel.
I have very little faith in Nosler and their testing, as they can't even get their B.C.s right.
I've done my own testing and I know that twist rate aids terminal ballistics in so much that it helps assure that the bullet hits squarely AND with some bullets surplus twist brings them closer to the point of mechanical failure and they become (in essence) "softer" and easier to expand...the best examples being bullets like the SPSX which will expand and penetrate like a normal JSP fired in a 1:16" but will act like an explosive VMAX if fired in a 1:9"
Those two bullets were Sierra Blitz, fired in a 1:16", which is technically unstable, yet since the soft point is inherently terminally reliable due to its design and mode of expansion, it expanded evenly. Fired in a 1:9" it would have turned to bird shot in the 1st inch of gel.
Attachments:
lou270
New Member
thetinkerer
No - I am familiar with the article you posted. The
impact to terminal performance and stability is related to fmj bullets and length of narrow channel. I already pointed out that stability has an impact here and there is no dispute. The length of narrow channel in fmj pointed bullets is well understood
As a matter of fact - here is the article that is refenenced in that one - apps.dtic.mil/sti/pdfs/ADA519801.pdf. A less stable bullet in this case caused bullet upset more quickly but that is neither here nor there for expanding hunting bullet. Trying to apply that broadly to other bullets is what I am disputing.
You seem to want to apply Litz’s sg needs to be 1.5 to optimize bc to expanding hunting bullet performance. I have seen no proof other than “it should” that these slight turbulences cause any significant change to expanding bullet performance. Think about it - you are shooting down on the animal or quartering to the animal in the field You are going to have far more change in angle of tip impact than 1 degree you get from a minutely wobbling bullet.
An expanding bullet doesn’t need to be ‘held straight” during penetration by twist. Sorry - but this makes the least sense given how expanding bullets work. The only exception being berger which behaves effecively like a fragmenting fmj design and has neck
However - we can agree to disagree on all this. I am happy to keep discussing it, but I don’t want it to turn negative as these posts do if go too long
One new thing to me is the effect of twist on petaled bullets. I knew something was going on there but could not put my finger on it. The fluting analogy helped
I also think it makes sense that faster twist can increase or at least make bullet expansion easier. Whether that is significant and good or bad thing depends on situation and bullet. I think the bigger effect here is probably seen in bullets designed to fully fragment. In any case probably good idea to follow what the bullet maker recommends in this case and not be shocked if you don’t and bullet doesn’t behave as intended
Lou
lou270
New Member
I am not sure why would want to dismiss the nosler data other than it does not agree with pre-concieved notions. I would say out of everything that is stated on the subject it is most relevant or at least removes the guessing. However I would agree it would be more relevant if there were more data as to bullet type. Based on response and context of article assume an expanding
design (ie do bullets expand more…). Dont really care on range.
As for BC, I would get Litz’s book Ballistic Performance
Of Rifle Bullets. Nosler is not the only one with “intlated BCs” though their 7mms seem about the worst. The 270 and 30 cal not so bad but still high. In any case Nosler is known for terminal performance not BC
Lou
tthetinkerer
Senior Member
Lou270,
I'll try to explain this step by step, because what is intuitive to me may not be to everyone. We KNOW FOR CERTAIN that BC is compromised when a bullet is not comfortably stable*. Why is that? Because pitch/yaw isn't yet brought to its minimum until it is fully stable. This is why I (and bullet manufacturers as a whole who all give minimum twists for theirs bullets) leverage Litz's findings on gyroscopic stability.
A hollow point generally needs to hit the target, drive into it some distance and fill the cavity with some fluid/-like substance which forces it open, and subsequent penetration and drag through tissue completes expansion. If your bullet is pitching/yawing too much at the point of impact it may not hit squarely or open up evenly which does affect terminal performance.
The best thing I can do is to get a second gel block and devise an experiment to show you and everyone how twist can affect terminal performance. Unlike dishonest Nosler, I will use multiple types of bullets with different expansion modes, all fired at the same speed, but in different twists (1:16" vs 1:8").
*full stability actually occurs around 1.4, and not 1.5, but to be safe and to compensate for non-ideal conditions 1.5 is suggested as a minimum
tthetinkerer
Senior Member
Because the Nosler data doesn't say anything about the kind of bullet or the distance. It doesn't really help the discussion about terminal performance of sharp petaled (monolithics). I already know that soft point and JHP style bullets don't care what kind of twist you use as far as their wound channels are concerned, but some modern styles of bullets do. I don't appreciate major MFGs that inflate/lie about BCs to sell their bullets when all they have to do is buy a labradar and be done with it (see attached USAF study).
Now, the Barnes stuff in that article DEFINITELY gives the relevant details and findings that dovetail the gel shots that Farleg showed (which was of Barnes 210gr TSX).
Attachments:
BC comparison.pdf (981.37 KB)
riceman
Global Moderator
Guys to help here i did the twist test in 1 gallon jugs of water.
Rifle used winchester 43 22 hornet 1-16" twist.
35hh 1.1sf. Mv 3100 distance 100yrds. Penatrated and came to rest in 3rd jug.
Only 1 petal came off and bullet tumbled after exiting 1st jug of water.
So decided try 12" twist 223 vanguard. Same speed and distances. 2 petals came off, same 3 jugs but tumbled exiting 2nd jug.
Tried 8" twist 223 ar. Same speed and distance.
Bullet lost 3 petals, 4th broken just never came off. Entered 3rd jug straight but no exit..
Only difference in this test was twist.
This was done 2 years ago.
Attachments:
riceman
Global Moderator
This is a good thread Harperc started a few years ago, may help
lou270
New Member
Thetinkerer
Yep - I get it on the small hollow point. This is a bullet design issue and the reason a big hollow point sits behind the polymer tips of most mono bullets these days. This is long lesson learned mostly with barnes growing pains. As I noted in previous post this is why increased twist can help with small hp. This was part of my point about following manufacturers recommendations.
I will admit I am a bit leary on this concept of small hp since I still believe an angled shot due to elevation or quartering animal will present the hp with a much steeper angle than couple degrees of wobble. What am I missing here. Probably why to this day barnes tsx still has rep of not expanding sometimes though ttsx does not
In any case this discussion turned some from does twist impact terminal performance to does bullet stability impact terminal performance. I am not so interested in this discussion as you noted that most manufacturers supply a min twist. I no way imply that you should use less twist than manufacturer recommends. Assuming you do this bullet will be stable and we are good
One caveat to keep in mind on the sg calculators is that they are approximations. So if litz calculator says 1-8 is stable (sg > 1.5) but hornady says 1-9 that does not mean the calculator is correct and hornady is wrong and you need more twist. The calculators do not take into account the design and density of the bullets (ie real center of gravity). Bullet designers do this when they design bullets. Hornady probably got tired of answering this question from bullet twist calculator jockeys and put out a youtube video
So back to question of twist impacting (assuming bullet is stable) terminal performance of big game bullets. Seems yes to some degree for petal bullets (more twist may make wider but less deep wound - no free lunch) not really for traditonal (ie non-petal) bullets.
Lou
farleg
Platinum Member
GDay the fur calculator is ready, just give him the nod
a lot has been learnt & riceman put up a good thread & a few others have also been chatted over & overwhelming for me is how far we have come & what we’ve learnt just like in this thread it’s fascinating stuff & I personally thank everyone for their input as I’m looking @ things with a bit more or less of a twist than I once thought of yep just trying to penertrate into the depths with more certainty
keep it coming
Cheers
harperc
Global Moderator
And some crayons to explain it to some of us
lou270
New Member
I am basically came to the conclusion of use a bullet that either blows the petals off for collateral damage or use a bullet that expands to front that doesn’t have them. If the consensus is you need faster twist to try and equal the damage why bother unless you just want more penetration and less damage to begin with
Interestingly that is what got me interested in hammers to begin with
Lou
tthetinkerer
Senior Member
Thank you for those pictures, I was always wanted to know what those little 35gr ballistic barrels would look like expanded! That should make an excellent predator bullet...
...no longer any need to buy Ballistic Bob's Beaver Busters anymore!
riceman
Global Moderator
Beaver busters.
farleg
Platinum Member
Gday
Tthetinkerer & lou
I feel like this thread has come to a end for which I kinda agree it’s better if it doesn’t get to long we won’t start rehashing the same points already put forward by you 2
I really really appreciate your time & others probably also
Way above my pay grade but I’ve got a lot out of the discussions by you 2 & paying a little more attention to a few points now really it’s already in the bubble but now it will be way easier to assess so thankyou again
As your fairly new here & If your curious or haven’t already done
Search up “ hammered down under “ thread as it was a great learning curve for me personally on the way hammers were behaving & put a few myths to bed & my mate who guides now uses the 248hh on his house rifle for buff & everything else that gets in the way
Twist to me is ever so important in my choice of pills & yes I like 2 plus of stability but I can live with some pills ( due to preformance) of slightly below 1.5 or around it as it’s just watching the bubble & fur calculator as they don’t lie in my world but I’m yet to see the results of more twist producing lesser results
Gel I’m careful of like other media tests but I really like looking @ it as it gives us great reference points & animal testing will always be king in my world as gel dosent run
Thanks again no offence intended to anyone
& I look forward to more civil discussions like this as it helps so many myself included
Yes this place is awesome
Cheers
lou270
New Member
Farleg
Read through the hammered down post and a coulple of questions/comments.
1 - From what I gather the consensus was that really high sg seemed to work better. Ie shank penetrated more straight vs tumbling
2 - Was the high sg accompanied by higher velocity? For ex, did you see cases where you had less tumbling but still high velocity but a normal sg , say > 1.5 but not super high like 2.5+
From a terminal performance standpoint what twist increases (rpm) is centrifugal force. While twist may not help the bullet deform
it will increase force in a perpendicular direction. So it may make a wider “mushroom” if bullet design allows or if you have weakened jacket for ex it may pull/tear off and get zinged away faster vs stay in 1 piece with a lower rpm. You can see this is varmint bullets for ex
Anothet thing I want to discuss is as I pointed out stability in game and stability in air are very different. flesh is at least 1000 times more dense. So a SG of 1.5 or 4 is big in air but it is .0015 or .004 in flesh. Doesn’t make a difference from a physics point of view (remember - shoulder stabilization). So if you have perfectly straight (>1.5 sg) then more theoretically should not matter. Again field results matter more - so bear with me I have a theory I would like you to think on basis on fur calculation…
Hammers are a but of a different animal in terminal perfomance. They blow the petals off and leave the shank. A normal big game bullet may fragment but in general the bullet mushrooms fairly uniformly out and erodes during penetration.
My theory as why shank penetrates better with increased sg (rpm) is that if you have petals not all tearing off at basically the same time you can create a significant instability in the core which may cause it to either veer off course or even tumble if say one petal stays on for even very small time longer. Increased rpms from higher twist helps the petals come off at same time ensuring no or minimal instabilities are introduced during petal shedding.
Anyway that is one thought that to me is explainable by physics why more twist may help keep the shank straight. Thoughts?
Lou
kneedeep
Full Member
Lou and tinkerer
I don’t have the time right now to join the conversation but have enjoyed reading this discussion. You both make good points and explain them very well.
Lou, I do like your theory above. I hope you explore it more and continue this conversation. I have discussed similar theories on hammers shedding their nose petals and shank stability. Although I did not think about the twist in your theory. Great stuff.
I would like you to think about what the definition of an “expert” is. There are academic experts that understand the physics and can write papers on the subject. But they may not have a full understanding of what’s going on because they don’t have the real world experience to see the hands on results of their writings. Then there are folks like Farleg and others on this forum who have the real world results and observations but may not be able to explain their results regarding the physics. Again why I think Farleg needs to whoa book on terminal performance. And not just with Hammers.
Hope you can combine all the information together.
kneedeep
kneedeep
Full Member
Great post as always riceman!
lou270
New Member
“ I would like you to think about what the definition of an “expert” is. There are academic experts that understand the physics and can write papers on the subject. But they may not have a full understanding of what’s going on because they don’t have the real world experience to see the hands on results of their writings. Then there are folks like Farleg and others on this forum who have the real world results and observations but may not be able to explain their results regarding the physics. Again why I think Farleg needs to whoa book on terminal performance. And not just with Hammers. ”
Agree - absolutely. I have plenty enough of my own experience with non-hammer bullets so the whole extra-emphasis on twist or high sg with hammers has me extra curious. I am not saying twist not important other places but apparenlty extra important here from reported results. I am challenging some of the reasons folks say it helps because it doesn’t jive with well understood iteractions. However, that does not mean, for ex, that I am disagreeing with farlegs results that more twist is better. Just thinking/discussing on what is reasons for it
Lou
kneedeep
Full Member
Lou, I like the way you think.
Some show extremely good results without high SG. Is it an ideally balanced pill (nose/hp/shank) for their velocity and animal resistance? All ,stable, hammers will outperform other designs imo.
Is higher SG a “band aid” to achieve ultimate performance in a pill that’s not ideally balanced for a given velocity and animal resistance?
There certainly doesn’t seem to be a down side to higher SG.
joe16
Platinum Member
Kneedeep
Sir I like the way you think. I think it would be a great read. That's if we could hold Farleg down long enough for him to write a book!!
Tales from Down Under my perspective on bullets and terminal performance. Something like that, but what a great idea!! There's even a few people on here that could give him a hand on some particular sized cartridges. Since he is, you know, narrow in his scope
A book, what a great idea
Joe
lightthetower
Full Member
“Bang, Flop, Calculate the Fur; a Love Story” by farleg
riceman
Global Moderator
"The view from upside down"
farleg
Platinum Member
G'day
you guys are killing me & notes taken on you all ,so sleep with one eye open i say may be advisable lol
Knee-deep now your on the recruitment drive I see hmmmm
Deflection is one I usually don't like but I'll settle for one now lol
I'm not interested in writing a book , man I haven't got enough time in the day now but I would gladly add a forward or whatever its called to a book if Steve ever does one & if he would even consider me to put something in it I would be honoured if that was the case
kneedeep so time you get onto Steve if you want me to put pen to paper lol as that's the only way I'd do it howz that for a deflection , I'd say a pretty good scapegoat
I'll keep one finger typing here while trying to get past spellcheck also as this place is my book I am humbled by the suggestion that I could write a book & appreciate all that you guys do for me as its way more than I can ever give
You guys are simply the best in so many ways
Now its back to the topic & my book lol
Cheers
farleg
Platinum Member
Gday lou & others please chime in & pull me apart
lou to answer your questions
1/ yes
2/ overall the greatest indicator was a higher sh showed a very consistent outcome regardless of velocity with no tumbling or minimal
as we got to the lower sg you could see a pattern of tumbling occurring ( most people will never see this as critter size the shanks gone before it would start ) on a more regular basis
from a terminal preformance standpoint::
I get a given twist flings off the petals due to more tork ( I may be wrong on my wording so please correct me ) & I was really worried going to a 7 twist in my 375 but I’ve been pleasantly surprised ( phew ) but I had to see actuals not theories, I’m better @ putting it in practice than a theory side as it’s so clear once I see the insides of a animal & reaction to the shot vrs me trying to assume on theory base
( guess that’s also just experience over many 100”s thousands of critters? Or ? But I do believe I’ve got a knack @ seeing what’s going on really quick & my mates have told me this many times over the years ( I’m trying not to come across as cocky so please don’t take it that way )
the zinged away faster if I’m reading this correct
a few of us have come to look @a petal /shank ratio that is showing in the same twist you get the ratio correct & the shank penetrates not just penertrates it does so @ a higher velocity & goes deeper ( parachute effect )
this to me goes with what you & tthetinkerer were on about in proper terminology so accept my apology for my hack version & just hope you can follow what I’m saying & I’ll also add this if you get this correct the tumbles @ the end isn’t as pronounced & it’s not just getting the petals out the way asap as more terminally to it than just that as other brands haven’t got it yet or maybe I haven’t but runs on the board go to hammers & this subtle difference is it I think
air & flesh stability : totally Agee they are majorly different resistances & even in same critter placement also big bones come into it ( higher sh is king here I believe)
& got you on hammers are different & even though other brands try to replicate they haven’t ( actually hammers perfected a system all ready done by others )
im ticking on your theory & got no right to dispute physics but it is also a little put up above that physics may suggest we have stumbled onto a easier quicker ride Just above my pay grade
then we get the bubble & how does that work as we get a massive smack like a frangible ( too higher velocities & fast twist ) but with the penertration of a wad cutter with a bigger wound channel all the way till it stops ( if you catch it ) but does lesson as it gets closer to its final resting place
now that’s on bubbles that go sideways you get the bubble correct ( help kneedeep what’s that direction explosive charge called again) & watch the magic happen & to me I’m leaning towards a higher sh than we once thought as I’ve seen no preformance issues & potentially iron out any shoulder stabilise issues that may show up especially on bone
( triangles parameters still number 1 )
no doubt I’m a spear freak as from my results nothing can match it on consistency ( if the pills capable ) but I’m also not worried with a low impact velocity as this is where hammers really shine over all other monos & a fair few frangible/c&c
( I can see the eyes rolling in a few heads now lol )
but penertration is the one that will ultimately get the most consistent results day after day year after year well it has in my world
shoulder stabilisation is critical in slower twists & im leaning towards a shank length to caliber ratio that may have no peers ( I’ve mentioned this a long time ago but no takers so anyone this time round )
speed of shank is also important & isn’t just the highest impact velocity achievable
the biggest thing I’ve taken on board is in the transitional zone & thank you & tthetinkerer so much for your discussion & you don’t know how much this has helped me on the picture I now see in my thought process
so thanks guys ( everyone) it’s the most wonderful conversation no right nor wrong it’s all learning/ teaching as that’s what you’ve done for me
now go pull me apart as that’s how we learn
& lastly you can put that in your book when you write it up kneedeep
cheers
no proof read sorry
tthetinkerer
Senior Member
Gentleman, specifically Farleg and lou270,
I found this the other day, and I think it is testing done in a crime lab under controlled conditions. It demonstrates that better stability factor will create deeper penetration before tumble, which is something that many here, including the designer of these bullets, have witnessed in viro (higher speed all things equal = slightly higher SG; tighter twist all things equal = much higher SG):
www.shootingtimes.com/editorial/handgun-bullet-stability/389036
The technician uses FMJ bullets which, like a Hammer shank, do not have a stabilizing shoulder. You will read how they test the very theory we were discussing in a limited fashion, and how the higher SG penetrates deeper without tumbling.
I know the physics says that the difference shouldn't matter in a much denser media, but it's like I said, I think the difference between higher and lower SG is set in motion at the point of contact before the physics of the more dense media is dominant.
Great discussion, guys. Seriously.
PS
We should name farleg's book "getting hammered: memoires of a self-proclaimed muppet"
farleg
Platinum Member
Sep 2, 2022 at 4:55pm tthetinkerer, lou270, and 1 more like thisQuoteEditlikePost OptionsPost by farleg on Sep 2, 2022 at 4:55pm
tthetinkerer Avatar
Sep 2, 2022 at 9:52am tthetinkerer said:
Gentleman, specifically Farleg and lou270,
I found this the other day, and I think it is testing done in a crime lab under controlled conditions. It demonstrates that better stability factor will create deeper penetration before tumble, which is something that many here, including the designer of these bullets, have witnessed in viro (higher speed all things equal = slightly higher SG; tighter twist all things equal = much higher SG):
www.shootingtimes.com/editorial/handgun-bullet-stability/389036
The technician uses FMJ bullets which, like a Hammer shank, do not have a stabilizing shoulder. You will read how they test the very theory we were discussing in a limited fashion, and how the higher SG penetrates deeper without tumbling.
I know the physics says that the difference shouldn't matter in a much denser media, but it's like I said, I think the difference between higher and lower SG is set in motion at the point of contact before the physics of the more dense media is dominant.
Great discussion, guys. Seriously.
PS
We should name farleg's book "getting hammered: memoires of a self-proclaimed muppet"
Gday tthetinkerer
thanks for the link I’ll read it as soon as I get time & I hope you can interpret my writing as I struggle myself sometimes as what my heads thinks then I don’t no how to spell a word ( spell check is frustrating for me sometimes) so I replace it with others that are hopefully correct or sometimes the sentences just don’t flow
so I guess that leads us into the ps
oh so your on the bandwagon now lol but I will say that’s pretty cool
thanks to everyone who contributes no matter how small it make this place awesome & the place I love
cheers
kneedeep
Full Member
I have to make this extremely quick, so you'll can hash it out one way or another. This thought process came from my start with percussion cap muzzleloaders. Large, low bc bullets, low velocity, 20 twist plus barrels and then wadcutters.
A stand out pill 308 124HH
Standard stability above
308 124 shank stability below
Above, assuming the shank retained 60% of it's velocity after shedding nose petals.
Shank bc estimated from a wadcutter similar to in size to the shank, below
Below is shank with increased twist.
Throw in lou270 shoulder stability on top of increased stability after tthetinkerer "transition zone" and I believe we can see where the physics start to play in our favor with increase twist for shank. No time to go into more details. Please run the numbers for yourself and make sure there are no mistakes here. I also believe there is a big difference between "stable" bullet in it's ballistic form and a "stable" shank (wadcutter) in it's terminal form. You did a great job of explaining that tinker. I also believe if the shank has FOC (forward of center) balance, there is increased benefit there. A bullet in it's ballistic or terminal form is rotating around it's center of gravity. Where this center of gravity is located makes a difference on whether or not it wants to move front first or tumble.
I also have a crayon drawing in mind to show some of this but no time to make them up.
farleg - "shaped charge" focuses the energy right where we want it. And boy did you get me to come full circle on that topic!
No time for proof read or further explanation. Please use a Tasmanian translator for this one
kneedeep
joe16
Platinum Member
Kneedeep
Very nice thought process, well put together. You'll have us scratching our heads for a few hours (how did HE come up with that??) before any replies I'm sure. Nice job, Birds must be flying good!!
This place is awesome
Joe
gltaylor
Global Moderator
As indicated earlier, there is a world of good information in the publication "Shooting Holes In Wounding Theories" by Mr. Rathcoombe.
The publication is very lengthy and in considerable depth.
I have made a "Cliff Notes" version of some of the more interesting points (to me) made by Mr. Rathcoombe.
If ballistics and wounding are of interest to you, this document may save you some time.
Major points made are cross referenced to where the full explanation can be found in the main text.
Enjoy!
SHOOTING HOLES IN WOUNDING THEORIES.odt (46.98 KB)
In addition, there are some good pieces written by Dr. M. L. Fackler and Nathan Foster if you care to search.
easttennjed
Full Member
Awesome! Thank you for putting this together!
farleg
Platinum Member
Great stuff George
Haven’t read your cliff notes yet that will be my bedtime story
The hard one for people to wrap their heads around well I had trouble is putting it all together & the 3 professionals mentioned above is putting it all together
That’s where I’m simple & take note of the fur calculator the break their findings down to my world
Just wish rathcombe would have done tests with hammers
& the one thing I’ve not seen anyone mention is the different forms of bleeding that occurs from mushroom vrs hammer
One is a crush the other is a cut & no not all monos are equal on crush or cut
Just observations & thanks again GL
Cheers
gltaylor
Global Moderator
Farleg,
You're right. Unfortunately, the nearest Rathcoombe came was very limited testing of the GSC bullets (forerunner of Hammers). He also did a bit with TSXs, but they don't perform at all like Hammers since they retain their petals.
His biggest observation was that monos probably are the wave of the future due to better penetration, even with less mass.
He talks at length about the superior penetration and damage of flat meplate bullets that crush and displace tissue at 90 degrees to the path of the bullet.
Since he never had or tested Hammers, he's unaware of the tremendous damage petals do when acting as independent missles, cutting their own paths.
Flat meplate cylinders (shanks) do more damage than smoothly rounded edge mushrooms! He got that part
kneedeep
Full Member
gltaylor Thank you again for all you do to orginize this forum and put a ton of information together in one place. It's amazing the amount of work you do here.
It's unfortunate they didn't have hammers in their testing. All the more reason for you to write a book on terminal performance farleg! You better get cracking because you have a ton of pics and on game results to organize.
Haha. Get that camp fire hot and your mates around to drag all the old highlights out of you.
kneedeep
jakesch
Senior Member
I do appreciate how he approaches cavitation and dynamic pressure. I know I brought up dynamic pressure on here before and it is good to see a more formal theory with that included.
I read the spark notes and now have started on the entire thing. Love this stuff!
gltaylor
Global Moderator
Jakesh,
There's some great information, graphics and illustrations too. I like pictures! They're easy to read
gltaylor
Global Moderator
Yeah Farleg, I agree! Just,please God! get somebody to write it for you!
(Just picking, but couldn't miss the opportunity to prod you
)meatbuck
Platinum Member
Thanks gl.
tthetinkerer
Senior Member
One other thing I noticed is that despite his breakthrough revelations, he still maintains some preconceived notions that limit his understanding of what I call reliable vs decisive kills.
Large caliber users cling to the passthrough principle because, while there may be some tracking, you can mostly assure a recovered game animal. This is mediated by deep penetrating, through and through wounding.
The smaller caliber users like varmint and predator hunters know that fragmentation and organ evisceration is where those instant, decisive kills come from. A varmint that runs off a few yards back to his den isn't looked at as the halmark of a successful varmint cartridge.
The author believes that the acclaimed .224 caliber 70gr JSP from Speer wouldn't be a good deer stopper due to limited penetration through gel, but the proof is in the tasting of the pudding: the fragmentation of the front half into the lungs and lodging of the retained half under the far side skin is enough to anchor all but the larger varieties of deer. Just ask the hunters who use it via their reviews on websites that sell the bullet. Even more successful are the 62gr and 75gr gold dots, as well as the 75gr TMK. Just don't aim at high shoulder or do any Texas heart shots...
Combining the properties of a reliable killing bullet (deep penetrating, passthrough) and a decisive killing bullet (fragmentation) gives you the newer generation of monolithics, such as the Hammer and its now discontinued spiritual predecessor the GSC HV, that outperform C&C bullets in every way save for cost and BC. There are other monos that also demonstrate this behavior down to moderate speeds, such as Cutting Edge. Others like Maker Bullets (tipped variety), Cavity Back Bullets, and Badlands Precision, intend to expand by design but in spite of their designers they still blow off petals at moderate impact speeds and above.
Others like Barnes, Hornady, and Peregrine monolithics are sticking with the old double caliber mushroom method. I think Patriot Valley Arms from range reports do something a bit different than all the others...some say they actually expand minimally and are intended to tumble...I saw some pics and the entry/exit wounds were a bit much.
kneedeep
Full Member
You have some very interesting points tinker. Thanks for sharing them.
tthetinkerer
Senior Member
Thanks. I'm just a youngster trying to contribute something to what I see are a bunch of guys with a lifetime of experience. I get a lot more from you guys than you get from me.
gltaylor
Global Moderator
Oohhh Boy! I'd hoped this would excite some extended conversation. I am constantly impressed by the breadth of knowledge here. Thank you all! Carry on!
farleg
Platinum Member
Gday fellas just having lunch here & not enough time to reply to ea but keep this discussion going as it’s so interesting
I think rathcombe is very good & if he was still doing tests he would have seen the evolution of pill design & his research potentially would have shown more insights into what’s going on & potentially finding out a shift in his data upto that stage of testing had shown
I do believe the base of what he is saying is correct just like I do Nathan foster yet these 2 guys are opposite ends of the spectrum on their thoughts in what kills better
so I’m greedy & take both these professional guys research as a really good position to look @ in finding a pill that works the best across hunting situations yes combing thoughts & take the best of both guys research of what’s happening in a critter , once we can get that part the rest is easy & for what I’ve seen hammer has got this better than anything else hands down but I know Steve is still exploring options to improve on a already great product & i for one with the help of others won’t let Steve rest on his loreals
Now on some of these “others”no need to mention names
Oh yes rest assured the poke is warmly taken & noted for which it will be given back in due time
My book ha ha yes kneedeep I take your nudge on board but I’m thinking mine is in here already & you lot are the writers lol
I think that what is more fitting & the proper book is when all the great minds have their inputs on the subjects as I’m only a very small part of the research we have found to lift the bar but one I’m glad to help where I can
Cheers
les
Senior Member
This is great stuff! Let's toss the third leg of the stool into the conversation, accuracy. Farleg is going to like this comment. Along with accuracy is also the speed we can get with light Hammer bullets. Low recoil, fast bullets lend themselves to a more accurate shot if the bullet is good. Hammer's design and manufacturing methods lead to a more accurate bullet. I'll just speak for myself, light fast bullets with low recoil are easier to shoot accurately. I must confess, I'm getting addicted to shooting the 85 grain 6.5 grain bullets at 3500+. Not much kick, and very very accurate! My mentor for hunting elk hurt his shoulder at work and could only tolerate the recoil of his 243. It was accurate. I saw him drop 4 elk in their tracks. He would only take a head shot and I never saw him miss in the 4 years I hunted with him.
kneedeep
Full Member
I have had this same discussion regarding the larger calibers. Dangerous game loads down to elk/moose loads. Recoil tolerance per individual plays the biggest role when making a decision. 100% agreed.
tthetinkerer
Senior Member
Ditto, KD.
When I was at the Fish&Wildlife managed range out in Holopaw, I was talking to a guy. He was genuinely dumbstruck about why I'd deliberately use a 223 Remington for a deer. He told me his story about the first deer he tried to harvest with some 30 cal, don't remember which exactly, but he was hit with nerves and made a gut shot. You can all tell how that ended. From there on out, he believed that anything smaller means that you could never recover a deer from a less than ideal shot.
I told him that his story illustrated that even a so-called deer cartridge can lose deer if your shot placement isn't right. It's just a matter of people finding something to blame other than the shooter. I also mentioned that you'll always shoot a lower recoiling cartridge better than a higher recoiling one. Period. How precise they are depends on the loading and the gun, though.
farleg
Platinum Member
Gday
Les , KD & tinkerer I agree 100%
=Triangle
The greatest thing we can do is no our limits & practice will show our limits pretty quickly then practice past our limits to move the bar
Caliber / range it’s all the same = practice
Cheers
jakesch
Senior Member
One thing I want to add that I read that I do not remember seeing in the notes: Cavitation is a function of bullet diameter, shape, construction, forward and rotational velocity.
I want to put the emphasis on rotational velocity, because we all now know faster twist rates produce better results and penetration...well per the author that is due to an increased ability to generate cavitation.
Higher rotational velocity increases static pressure on sides of bullet. This would also increase permanent would cavity.
gltaylor
Global Moderator
jakesh,
Thanks. I bet that's not all I missed. Please save me the trouble and provide the reference. I'll edit the original and re-post.
All of you - if something really piques your interest, please do the same.
The reference is for the benefit of ALL!
(Oh, and increased stability factor is now so important to me the last 2 barrels I got have Much faster twists.)
farleg
Platinum Member
Gday GL
pictures
X2 on stability & we still have yet to get slippage with hammers with some pretty quick twists
jakesch im sure your going to pull a lot more for us simple minds thanks for the addition
cheers
lou270
New Member
This is a good page but the guy is fundamentally wrong on several points. Probably the main one is that temporary cavity is not important to hunting. He is obviously a big / medium bore aficiando and though he has a lot of correct data he points you in that direction with half truths.
The temporary cavity is enormously important for high velocity cartidges. If it wasn’t we would all be hunting Elk with our carry handgun that often has unexpanded bullets let alone expanded bullets the same or larger diameter as our popular 24-30 cal rifle cartridges fully expanded
The temporary cavity though “temporary” in duration has a significant impact on wounding in high (2000fps+) impacts. Tissue is elastic but it is not unlimited. In a typical rifle wound the temporary cavity will expand many times bullet diameter and then shrink back to a size somewhere between bullet diameter and max temporary cavity for the permanent cavity. ultimately the permanent cavity settling to bullet diameter as velocity slows then a bit less than diameter as the bullet pushes through vs crushing during penetration. Outside of this “hole” in the area damaged by temp cavity there is a zone where tissue is damaged but not necessarily torn. In this region there is free bleeding damage to blood vessels. Outside of this there is tissue that is stretched but undamaged. The volume of the temporary wound cavity is proprtional to the energy and the diameter to the area and velocity squared (drag)
The temporary cavity forms after the bullet passes. Any fragmentation (ala hammer petals) weaken the tissue so the stresses from the temporary cavity then rip these apart which may only stretch without damage from fragments - greatly increasing the magnutude of the permanent wound
All of the above is clearly documented some of the literature mentioned (Fackler) for ex. There is a theme in ballistic wounding related to hand guns that penetration is only thing to worry about. This is true, because there is not much energy there so penetration is limited and there is no permanent wounding from temporary cavity because velocity is too low. This is also true for hunting very large game where you need all the penetration you can get because though something like a 458 is big compared to a deer it is a spitball compared to an elephant. For vast majority of hunting you have more than enough energy for sufficient penetration and cavitation adds signifantly to wounding.
I “think” this guy is extra skewed by Fackler’s work. Fackler seemed like he was on a mission to de-emphasize the temporary cavity. If you understand his work this is because at the time (70s ish) there was a big push that energy is the main reason to select a cartidge and that the entire temporary cavity (which can be very large) causes wounding. The media got on this and Fackler stated that Surgeons would remove tissue from the entire area of a high velocity wound impacted by the temporary cavity vs. just removing what was damaged. Also around that time there was a push to declare the 5.56 as cruel due to the large temporary cavity. Fackler was on a panel to contradict this
In any case; like anything on the internet take that site with a grain of salt. Lot of good stuff but also misleading conclusions.
Lou
PS. Looks like tthetinkerer thought about the same thing. I read his post after mine so sorry if redundant
lou270
New Member
ne of the wounding literature states cavitation is a function of rotational tvelocity. In fact, they state rotational velocity has little to no impact to wounding due to having very small energy (less than 2% of total KE). Cavitation is proportional to the drag on the bullet and vast majority of this is on the front not the side except possibly on “petaled bullets”
I don’t think that “petal” type bullets were thought of in this light. By petal I mean barnes x and not hammer type where they fly off. In a “normal” mushroom you do not have the spaces between the petals so a more uniform area is pushing stuff aside. In the petal bullet there are gaps between petals. Those cause the nice swirlies we see in ballistic gel and are there because the material is flowing off the tips of the petals. The bullet is actually displacing less material (ie less wounding) comparer to a “mushroom” which is why these bullet types penetrate more. Otherwise the spinning is there in all bullets but do not notice is in gel since material is getting pushed away uniformly. Spinning faster may make it look like the bullet is doing more but it is still contacting the same amount of material ( ie the bullet frontal area is not growing) across the same distance
That being said for petal bullets the sides of the petals are contacting material. So that small amount of KE may come in to play there. I don’t think it would on a bullet that does not have petals
Anyway that is my take on it
Lou
lou270
New Member
If you think I am full of it, all of this info is in:
Bullet Penetration by Duncan Macpherson
And
Wound Ballistics by Kneubeuhl
I may be full of it, but I try and base it on research
Lou
kneedeep
Full Member
Lou
Thanks for taking time to post all of your points. I always love to see the reference material added with some common sense thoughts. It is a great conversation.
kneedeep
gltaylor
Global Moderator
Good!
Once again we have additional references and healthy discussion. I am constantly amazed at what many very smart people glean from the same studies.
Only problem is, now I've got more to
read.Thank you all!
Seems like all the "gurus" can do is agree to disagree?
farleg
Platinum Member
Gday
Lou & or others cavitation is the one I’d like to delve a little more into
I do think it’s underrated just not smart enough to put on paper my thoughts especially @ the moment as I’m about brain dead lol
Could you give a little more thought on how as we increase velocity the cavitation increases by how much ( I note the 2000+ velocity so what’s it like @2500 then 3000 & so on ) & do you think one of the reasons hammers make the animal bleed out more ( they just drain the blood out of the animal way more than any other brand )
Just ticking not baiting
Cheers
tthetinkerer
Senior Member
Very good take, and I'm glad you figured out why petal type expansion penetrates deeper than mushroom style...
...but the only thing I will correct is the idea that the rotation has no difference in tissue contacted with petal type expansion. It does. Think of the reverse, which is what we do with barrel fluting. Which removes more material: straight flutes, 1-12" flutes, or 1-8" flutes? The faster the twist, the more material that is contacted and stripped.
Like you note, rotational energy is small and generally plays little to no role in the permanent cavity...unless you use sharp edged, petal type expansion. Hunting with broadheads show us that not much energy is needed when you use a more efficient wounding method, i.e. cutting with a sharp edge, versus brute forcing your way through.
We agree totally that like just about all of us, the author has a bias one way or the other (in his case, in favor of big bores). I just spoke to an older hunter on YouTube about the 100+ deer he's taken without a single failure using the 223 Remington and...the 55gr VMAX. That would definitely send the author of this wounding theory into a fit, but I know how powerful the temporary cavity is so I don't doubt it!
cbjr
Senior Member
Just because I had to know...
Based on a 30-06 as an example:
After using various online calculators, a 150gr bullet in a 10twist @ 3000fps, rotational energy is 14.025 lf-lbs, which is less than 1/2% of forward energy. 14 isn't nothing, but very small in relation to forward energy.
Side note: the answer took longer to achieve than I had planned. Lol
tthetinkerer
Senior Member
You'd be surprised how little ft*lbs are involved in a stab wound or a cut with a knife. Again, I think if we're dealing with sharp petals, the energy doesn't need to be big especially when the temporary cavity is already stretching the surrounding tissues to their elastic limits.
pubmed.ncbi.nlm.nih.gov/27503509/
According to this study, it only takes between 11 and 16 joules (8.1 to 11.8 ft*lbs) to completely stab pig ribs with a Swiss army knife.
farleg
Platinum Member
Aug 26, 2022 at 7:21pm tthetinkerer likes thisQuoteEditlikePost OptionsPost by farleg on Aug 26, 2022 at 7:21pm
tthetinkerer Avatar
Aug 26, 2022 at 6:40pm tthetinkerer said:
cbjr Avatar
Aug 26, 2022 at 5:35pm cbjr said:
Just because I had to know...
Based on a 30-06 as an example:
After using various online calculators, a 150gr bullet in a 10twist @ 3000fps, rotational energy is 14.025 lf-lbs, which is less than 1/2% of forward energy. 14 isn't nothing, but very small in relation to forward energy.
Side note: the answer took longer to achieve than I had planned. Lol
You'd be surprised how little ft*lbs are involved in a stab wound or a cut with a knife. Again, I think if we're dealing with sharp petals, the energy doesn't need to be big especially when the temporary cavity is already stretching the surrounding tissues to their elastic limits.
pubmed.ncbi.nlm.nih.gov/27503509/
According to this study, it only takes between 11 and 16 joules (8.1 to 11.8 ft*lbs) to completely stab pig ribs with a Swiss army knife.
G'day fellas
Nice info
Now what happens @4k to those figures & the stretch & cut by petals is very correct & not understood well in my world
Now also why is the hide parting from flesh that no other pill design I've ever seen accomplish ( only on certain critters) &also here's a bit of info to work out why the difference
375 cal
137sh @3800 in 12 &7 twists ( various range impacts ) the 7 twist is superior on the critters I've shot not that there is shabby but a difference none the less
A Simple mind like me visualise it in a outboard motor prop the way you just cruise along vrs a full throttle & you just look how much water is displaced
Cheers
tthetinkerer
Senior Member
Yep, farleg is right. In the varmint calibers, hunters have noticed for a long time that bullets with faster twists just "splattered" critters better for some reason, and they couldn't understand why exactly.
What I think many of us don't consider is that it requires kinetic energy to deform a bullet into its final, terminal form (initially, that KE is donated in the form of velocity). Higher twists impart a state upon the bullet that allows it to reach its terminal state easier...kinda like how an enzyme lowers activation energy and allows reactions to happen faster or with less energy than otherwise. The reason for this is the additional stress that high RPMs place on a bullet.
KE translates into deformation via contact with another object (i.e. impact), and faster twists lower this threshold somewhat. The effect is more dramatic in lead core bullets.
farleg
Platinum Member
The splat word now where talking it’s gone into hiding for a while
the transfer of this energy is the one that’s the hard part to get correct/ consistent over the wide ranges of velocities / calibers
Woh just hold up a bit I seem to be warming to all this energy talk
it’s all good I think as I don’t mind saying or using it when it’s put in context like you guys can do
cheers
lou270
New Member
There are not a lot of satisfying, or concrete, answers on ballistic wounding. Seems the majority of study focuses on handgun and most rifle is based on military/fmj
As for temporary cavity (TC) a few rules of thumb from books I have:
Total TC volume is proportional to KE and density of tissue
Diameter of TC is proportional to KE transfered to target at that point in time
Assuming same sectional density, diamater of the temporary cavity is proportional to velocity
Assuming same energy, temporary cavity will be wider and shallower as sectional density decreases and longer and narrower as sectional density increases
The stress from temporary cavity only damages tissue when exceeds the elasticity of the tissue. Some tissues like muscle and lung are more elastic and some tissues are less elastic like heart and liver
Handguns and other low velocity rounds generally do not have enough energy for stretch from temporary cavity to cause permanent damage
I have not seen solid numbers but few sources say somewhere between 1500-2000 fps is where damage from stretch cavity starts to happen. I also read somewhere there is an increase at around 26-2900 fps but don’t remember where
Lou
gltaylor
Global Moderator
Lou,
Well said and concise points! Based upon my limited testing, I'd have to agree with every point from what I've seen.
Tinkerer,
You too are right on point.
I can't explain the science or technical part - but I can promise you that moderate to light bullets at very high RPM (fast twist) and higher velocity is devastating to tissue.
Speaking of elasticity - I was dumbfounded at how much the paunch/stomach could stretch and capture the "energy bubble", velocity and penetration ability of my fast bullets. It's like a huge catcher's mitt!
cbjr
Senior Member
tthetinkerer pretty interesting on the stab energy!
farleg
.375 137gr 3800fps
1:12 - 21.163 ft-lb (228k rpm)
1:7 - 62.2 ft-lb (390k rpm)
tthetinkerer
Senior Member
Lou270,
The reason you've read different numbers on the minimum velocity for temporary stretch cavity damage is because it's different for different weight and diameter bullets. Think about it:
1) velocity is a greater contributor to kinetic energy with a lighter bullet than with a heavier one, given the same total KE
2) a wider diameter bullet expends its energy more rapidly than a narrower one, given the same total weight.
That higher velocity threshold likely applies to the smaller caliber with their lighter bullets. The lower number likely applies to lighter constructed, big bore legacy cartridges.
---
Gltaylor,
Yes, smooth muscle tissue in the abdomen has a much, much greater elastic limit than cardiac or skeletal muscle tissues. I'm pretty much certain at this point that a hard quartering away shot is a no go with my 22 caliber on deer sized creatures.
harperc
Global Moderator
The splat word now where talking it’s gone into hiding for a while
In deference to the addition of better educated folks in the conversation!
harperc
Global Moderator
Good post! A&P being at the very least as complicated as terminal ballistics. Conversations combining both=lions and tigers and bears OH MY!
gltaylor
Global Moderator
Tinkerer,
I'm with you. Based upon what I've seen, I'd keep my very fast light bullets to broadside or slight quartering if i want full penetration. If you just want to capture a shank for study, hope you've got a metal detector (I used mine to find my recent shank). It's very messy and you'll have to hunt your shank in the junk. My 103PH shank made it through the paunch/guts and into the off front shoulder. It was easy to find the shank with the metal detector and cut it out. Gutting and washing the deer was messy
. Total penetration was 17". BUT I CAUGHT A SHANK!gltaylor
Global Moderator
Oh, and Harper, you crack me up. I laughed out loud!
Thank you my friend
lou270
New Member
tthetinkerer said:
....but the only thing I will correct is the idea that the rotation has no difference in tissue contacted with petal type expansion. It does. Think of the reverse, which is what we do with barrel fluting. Which removes more material: straight flutes, 1-12" flutes, or 1-8" flutes? The faster the twist, the more material that is contacted and stripped.
Yes - this makes sense for petaled bullets. I personally dont think it is a big impact since the bullet is travelling forward at high velocity but it is there. Of course you would decrease the penetration some, but these bullets generally have more than enough to begin with
Similarly on fragmenting (ala varmint) there is more centrifugal force to whip these fragments off in a shorter distance. Why more pop on small targets
One myth I do see repeated is that faster twist keeps bullets on straight line in tissue. A pointed bullet will yaw in flesh no matter
the twist we impose. At absolute best you delay the yaw a small amount by having more twist. Bullets become more stable the farther they go so in case of a fmj you may see it penetrate an inch or so more before it starts to flip but that is it. What keeps bullets stable in flesh is shoulder stabilization. This happens when hunting bullets expand and have a larger front. The forces pushing on the outside edges (shoulder) are greater than forces trying to over turn it so keeps it going straight. Wadcatters for ex are a very stable bullet for straight penetration. Of course the bullet can hit something inside or expand irregularly that causes it to flip but shoulder stabilization is what keeps it “point forward” not spin once inside tissue. This is because tissue is many times more dense than air so the geometric stabilization imposed by spin is not a blip of what it needs to be in flesh. Best you can do is keep as stable as possible on entry but this sort of comes for free as noted bullets get more stable the further they travel
Lou
farleg
Platinum Member
Gday Lou. Like This...
Also are you saying a 12 twist vrs 7 in 375 cal will penertrate the same & in 30 cal a 11 ,10&9 twist will also penertrate the same all with the same bullet & same critters but I do note it’s hard to get consistent resistances due to subtle to major angles & what the pill plows through on its final resting place if it dosent exit
?
I’ll be straight with you& not bait as myintent is to hopefully find a reason what’s going on as I just don’t know & I’ve found these discussions enlightening & I won’t take offence just trying to put the puzzle together a little more
my terminal results are showing differences & the wound channel is staying wider for longer
now is this potentially from the bubble created @ impact & giving the shank a free ride or getting vacuumed along
this is with shedding type pills not only hammers solids show a little different traits
Cheers
ps I don’t personally like editing for myself so if I’m miss reading what you’ve put up Lou please set me straight & get me on the correct path
Once again no offence will be taken cheers
tthetinkerer
Senior Member
I will agree with you that it's the frontal geometry that keeps a bullet straight after expansion and not really twist...but twist is responsible for the transitional stabilization you need before full stabilization can occur.
With many hunting style bullets (soft points and ballistic tips) expansion or the beginnings of it are initated at the very point of contact--they begin to form a progressively more stable complex the moment they touch game. Really wide hollow points are the same. Each of these three expands primarily by way of friction.
Your sleeker BTHPs or OTMs will need hydraulic pressure to open, where friction can later take over. It needs to enter game a certain distance and pressure needs to build before any semblance of expansion can happen, though. This is where you need enough twist to stay stable.
Also, odd angles, inconsistent and uneven tissue densities can throw a bullet of course. Extra twist can help mitigate this. Some bullet types are more susceptible to this issue as well i.e. hammers, tsx, bergers, etc. while some are not i.e. VMAX, gamekings, gold dots, TNT hollow points.
gltaylor
Global Moderator
OK, you smart guys have just about outrun my headlights...
I'm trying to stay focused on Hammers and how they perform/act on impact and afterwards.
Upon impact, they shed their petals and basically become wadcutters in shape. There should not be any petals left in tact on the shank in ideal conditions. The petals become additional missles - but that's another subject.
In the process of shedding petals, a great deal of energy is used to form a very large (hopefully) and deep "bubble" (temporary wound cavity) as the shank travels forward through tissue-bone, etc.
We're not concerned with pointed bullets (fmj) or those that form mushrooms - because Hammers don't do this.
(I'm not being argumentative or trying to be offensive. Just trying to sort through all this info to learn and gain understanding)
Several of us do autopsies on animals to learn about Hammer bullet behavior after impact at different speeds, angles and bullet weights. We think we've learned that higher stability factor (rpms) translates into straighter penetration paths. It also seems that more highly stabilized bullets are less affected by impacts involving bone?
Dangerous game hunters have followed this logic for many years. They demand straight penetrations measured in Feet, rather than inches!
So anyway, that's my 2c worth. Just trying to get myself grounded so I can try to keep up with you guys
lou270
New Member
Farleg - yep, that looks like it on shoulder stabilization. As for twist vs. penetration I think it depends. These are loose rules, but for a given amount of KE if for the bullet you are using the twist increases the diameter of the wounding it will most likely reduce penetration. In that sense it is having the effect as more frontal area.
Here is probably the best ex i can find of what I am trying to say on twist vs terminal perf. This is from the new super fast twist 1/3 8.6 round. You can see that doing a 3x increase in twist caused what looks like a wider wound to start and shallower as it goes along. I think this is because of what me and tthetinkerer talked about - the faster twist allowed more tissue contact for the petals (these are petaled / mono bullets) so got more radial damage but this means bullet slows down more as it travels due to higher drag. I still dont think you will see any or much difference in a front that does not have petals whether it is the hammer stub or a typical rounded mushroom.
If you are seeing the wound stay wider for longer with hammers with faster twist where petals come off, the best guess I have is that when they come off the faster twist flings them a little further away from the base. So, as the temporary cavity forms behind the base as it is going through there is ruptured tissue further away that is weakened so as the stretch cavity reaches this it detaches things further away so the permanent cavity is larger. Pure speculation on my part though. You would also need to be shooting a round with lot of energy and velocity to take advantage of this I would think. It may actually hurt 'less powerful' rounds if their stretch cavity does not reach what the petals are damaging.
Lou
lou270
New Member
Your sleeker BTHPs or OTMs will need hydraulic pressure to open, where friction can later take over. It needs to enter game a certain distance and pressure needs to build before any semblance of expansion can happen, though. This is where you need enough twist to stay stable.
tthetinkerer
The reason these bullets come apart is because they start to yaw and present more area. This is exactly what happens with the m16 round, which is perhaps, the most studied high velocity bullet of all time. In the case of the m16 round it splits at the cannelure generally. Stagnation pressure is proportional to velocity squared so it actually goes down as the bullet penetrates. However as stability goes up, such as at greater distances, the bullet starts to tumble later since it enters more stable
Here is from book Wound Ballistics:
I expect this is how things like berger vld behave as well and why their hunting bullets have thinner jackets than their target bullets. There is no lead or hollow point to initiate expansion so a thin jacket ruptures as more force is applied to it when starts to yaw.
harperc
Global Moderator
I'm going back to bed and will try later.
lou270
New Member
If you think about it, hammers will behave exactly like a barnes X type bullet until the petals shed. By that I mean it will expand to a wide frontal area and then the petals will break off and go their own direction causing additional wound tracks. This period of 'wide' is what will cause the biggest 'bubble'. The base and the petals will keep going and the temporary cavity that formed behind the 'wide' and now 'narrow' base will tear things up beyond the crush cavity until the bullet slows down during penetration. Tissue already weakened by the petals will likely tear so long as they are not so far away from the main wound track that there is not enough stress from temporary cavity to do so.
There is nothing different about a hammer than a fmj or mushroom bullet. All the forces acting are the same. I figured the comment on twist not affecting penetration would raise some hackles but think about it. You need a sg=1.0 to be stable, meaning you are keeping the bullet point forward basically. sg 1.0 in air is like .001 or .0001 in flesh. I don't know the value but the point is the small differences in twist we are playing with - 1 in 7 to 1 in 10 is not going to change the stability in a much more dense medium significantly. For DG it could be that since they are dealing with such short distances and increase in twist causes a better angle of incidence at impact keeping things more straight. As noted you get this naturally during hunting as rotational velocity decreases much slower than forward velocity, but for DG you are not dealing with distance.
Any case, food for thought. I'm still learning on this topic and the more you read on this stuff the more questions you tend to have
lou270
New Member
Here is video on shoulder stabilization:
tthetinkerer
Senior Member
Lou270,
A boat tail hollow point will yaw if it doesn't expand, but that isn't the intended terminal effect...it's to expand, hence the hollow point part. Maybe not "match" bullets, but hollow points in general.
I think you may be arguing against yourself, here. Shoulder stabilization does take over as the stabilizing factor in tissue, but a sufficiently fast twist keeps the bullet straight long enough to expand the shoulders out. Oh, and SG of 1.0 is NOT fully stable. It pitch/yaws as it comes out of the bore. It's only stable enough that it can overcome the drag forces and can "settle down" a ways downrange.
The two clear gel shots with the 8.6BO show just what I was trying to tell you. A faster twist will place more forces against the bullet to come apart/deform, allow it to happen easier, so shoulder stabilization happens sooner.
We actually agree, you just don't know it
lou270
New Member
Not really in agreement but I will state my case
A bullet expands because the pressure on it exceeds the strength of the material. At this point the bullet effectively starts behaving like a fluid and deforms until the force is less than that holding it together. This is caused by the stagnation pressure in a fluid like material and is proportional to velocity squared. Otherwise it is “harder” the faster the bullet impacts it. For ex you shoot a steel plate at 1500 fps and your bullet blows up. You shoot a deer at 1500 fps it will not expand. You shoot a deer at 2500 fps it expnds nicely. You shoot a deer at 3500 fps the bullet may shatter like hitting steel. Twist has very little to do with it. However for any fragments eroding off they may get zinged off faster/sooner with faster twistFor a typical lead / copprt bullet or hollow point designed to expand (not match type) the expansion happens immediately and is done in the first 1-2” of penetration. By this time the bullet is fully expanded to terminal shape. The lead tipped bullet gets the pressure at the tip, for the hollow point it fills and the pressure pushes outward. So there is no “stabilizing” in flesh needed assuming bullet is point forward. You could have a situation with a small hollowpoint where the angle at impact will keep fluids from entering the cavity before the bullet yaws but very unlikely to see this behaviuour with a lead soft point or decently wide hollow point. So faster twist may help here but by the time a bullet travels a little way down range (goes to sleep) shouldn’t matter. This is probably why the HH have pretty conservative twist recommendations. They have a pretty small hollow point and will be imporant to keep point on as square as possible. But just because it helps here does not mean it helps everywhere in terms of expansion nor does it mean there is anything wrong with the design. Just need to keep it in mind and probably why people sometimes report problems with the original barnes tsx and expansion.
As we discussed already for a petaled bullet the twist can help cause a wider wound because it is helping contact more tissue over a shorter distance. The forward velocity is what is causing the damage. You would not likely see this in a uniform front bullet since bullet presentation to the material is not changing. You can see that in the 8.6 pic. It has a wider wound to start but the slower twist has a wider wound towards the end. You just spend more energy up front but wound volume ends up about same just different shape. Anyway that was what I was trying to show with that pic.
Lou
farleg
Platinum Member
Gday I was up 3hrs ago & went back to bed also Carl
Now I’m back up cows are a happy & im in nunaland cause I’m stuck for words but rest assured I’m a ticking thanks heaps guys just trying to place what I’ve seen to what has been put up
So this is it for now
No hackles up here
Just seen the second use of the word “ stub “ definitely seeing I’ve lived a sheltered life
Trying to decipher why it’s applicable to DG & not your everyday deer shooter
Puts another side to the petal/shank ratio
Hydraulic & friction
Lots of big words that I have to look up the meanings of
Yep time for some work & tick some more
Thanks guys you have made my day more interesting
in a nice way I’m not being smart just thankful how it’s a good conversation without the usual crap that comes up on other forumsThis is the best place
Cheers
tthetinkerer
Senior Member
Lou, it seems like you're having trouble seeing the forest from the tree right in front of you. The statement that "twist has very little to do with it" is, to put it bluntly, false.
RPMs (a function of both velocity and barrel twist) place significant stress on bullets radially and this compromises their mechanical properties. Some bullets (such as Hornady's SPSX or Sierra's Blitz lines) can have so much force placed on them by the RPMs alone that they start to come apart from drag forces alone!
The reality is that people much smarter than all of us have already explained that there is a difference between the stability needed to punch paper and the stability needed to keep a projectile straight long enough to expand after impact with an animal. All the bullet manufacturers, ballisticians, and people like Litz are not all lying.
Furthermore, hunters in the South African and Australian brush figured out long ago that a faster twists keep their big game projectiles on track to hit the vitals better.
Both of these things had to do with something I talked about earlier: the transitional zone between external and terminal ballistics. That's where the twist matters most for stability on game.
lou270
New Member
Thetinkerer
I am still looking for an expert to say where twist has an impact on terminal performance. I am not trying to be contrary just stating what I have found. None of the experts who study this stuff, perform surgery on it, do experiments, perform autopsys, etc. that I have found give any credence to twist contributing to terminal ballistics. The only place I see people claiming twist has a big impact on terminal performance are on forums like this one
Below is an example and and you will find similar from “the experts”:
Rotational energy in the bullet has sometimes been proposed as a potential WTI mechanism, but this energy is too small to be important. The kinetic energy of rotation is always less than 2% of the translational kinetic energy (1/ 2mV2) even with a fast rifling twist, and is considerably lower for most bullets. This rotational”
kinetic energy is usually not included in conventional ballistics tables, and properly so, as it is too small to have any dynamic significance other than to provide gyroscopic stability to the bullet in air.”
— Bullet Penetration: Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma by Duncan MacPherson
a.co/9zUJ017
I would very much like to see a quote or paper from Litz that addresses this for ex so if you have one I would love to see it and learn from it. However I am not too interested in anecdotal evidence. I have my own on that and am trying to not let it interfere with research I have done
As for varmint bullets blowing up this is at least partially if not
mostly caused by increased structural strain and friction to the jacket as it travels through the bore at high velocity in faster twists than the bullet was designed for.
Lou
lou270
New Membe
I will also add that the only place I see what I would describe as the transition zone you are referring to is in the penetration of fmj spitzer bullets. The bullets have a narrow initial wound track called the narrow channel. However the bullets start to yaw as soon as they enter flesh. This yawing builds on itself and the bullet eventually starts to turn over. If the bullet comes apart you get a big wound at this point, if not it is a significant wound (like an expanded bullet because more area is in contact), then it completes the flip and travels base first.
The stability in air can impact the narrow channel length as the greater the angle of incidence (nose angle) at impact the more quickly the bullet starts to yaw. So the more stable the longer the narrow channel part of wound. There is no “narrow channel” in an expanding bullet track as noted because expansion starts right away where dynamic pressures are highest not later after velocity slows down
I will look around some to see if I can find any influence to twist (ie stability) referencing bullet expansion as may have missed something.
Lou
lou270
New Member
Seems split on petal vs no petal bullets. Lol:
www.americanhunter.org/content/does-a-barrel-s-twist-rate-affect-bullet-expansion/
Lou
farleg
Platinum Member
Lou
Gday Lou
the fur calculator is all they need lol
interesting points from you & tthetinkerer
siting on the sidelines watching & ticking
cheers
gltaylor
Global Moderator
Lou and tinkerer,
Well past my headlights now. Just gonna step aside and enjoy reading. Maybe something will click. The "experts" can't even agree. What do I know?
Carry on. It's great dialogue
harperc
Global Moderator
I'm enjoying this conversation immensely Lou and tinkerer. Kind of like a dog watching it's owners talk, I catch a word now and then.
It's definitely the deep end of the pool for me, but I'm paddling.
I've been a proponent of faster twist for multiple decades, and can't say my mind is fully open, but I'm trying.
Thanks guys, I'll keep checking in.
lou270
New Member
I have been enjoying discussion as well. I have been exploring / researching the literature lately so nice to share it somewhere and have a rational chat with interested folks and get few differing ways to look at things
Lou
tthetinkerer
Senior Member
Lou270,
Couple things to clear up with you. I never said that twist rate plays "a big role" in terminal ballistics. As long as the bullet is fully stable (roughly 1.5 SG or higher) or marginally stable and fired at a target at a distance far enough for the bullet to "settle down" it's being twisted fast enough. On the other hand, some bullet types (soft points, especially so-called semi points) are less prone to veering off course at impact due to how they expand and/or their geometry. If you've read enough about gyroscopic stability, you should understand that the models are just that--models. They are based on a lead core, boat tail spitzer bullet. Not a stubby little flat based cast lead bullet, or a very long VLD style monolithic bullet. What may read as a 1.5 SG may actually be higher, or it may be lower...in those cases it pays to have some extra twist to assure you have proper stability.
Second, this transitional area I'm talking about, and I'm not sure how you haven't figured out what I mean yet, is the place where the bullet transitions from external ballistics to terminal ballistics...it happens when the bullet hits the animal! (Marginally) stable bullets can easily veer off course here, or begin to tumble instead of begin to expand. What you thought I was talking about concerning penetration is actually called the neck, and any bullet's penetration path can have a neck, not just FMJ types.
Read pages 9-10 of the attached. Pay close attention. Read between the lines and use you own deductive reasoning. The role of twist rate in terminal ballistics is outlined. If a bullet is not fully stable, it still has significant nutations that affect the angle of attack. The AoA has a significant effect on what happens when it enters the animal. Hollow points may just fold over and not expand if they don't hit square. Sufficient twist helps to assure that it does hit squarely and it stays that way until it can enter into the tissue enough and form a shoulder/mushroom. Soft points are the most stable in this regard, as they don't need to enter the animal to form shoulders...it begins the moment they contact the animal.
You seem smart enough not to need an "expert" to tell you those things in plain English, but rather should be capable of deducing it from the examples they're giving you a long with all the understanding you've obtained from internal, external, and terminal ballistics, along with knowledge about stability and material properties. The amount of research you appear to have been doing may be lost upon people who believe in assuring suffient twist rates on game on "these kinds of forums."
Attachments:
Terminal_Ballistic_Performance-1.pdf (973.54 KB)
tthetinkerer
Senior Member
I just read the article and it's full of holes. My God, seriously...?
First, what kind of bullet was Nosler using? Was it hollow point spitzer? A dum dum? A ballistic tip? Lead core or monolithic? What was the target distance? I can assure you, a hunting bullet from a zero twist barrel will not expand the same as a twisted on unless it's at point blank range and it's a soft point.
Barnes demonstrated exactly what was originally proposed in this thread, and EXACTLY what I was saying about faster twist with sharp petals on a monolithic cutting more tissue as it creates a wound channel.
I have very little faith in Nosler and their testing, as they can't even get their B.C.s right.
I've done my own testing and I know that twist rate aids terminal ballistics in so much that it helps assure that the bullet hits squarely AND with some bullets surplus twist brings them closer to the point of mechanical failure and they become (in essence) "softer" and easier to expand...the best examples being bullets like the SPSX which will expand and penetrate like a normal JSP fired in a 1:16" but will act like an explosive VMAX if fired in a 1:9"
Those two bullets were Sierra Blitz, fired in a 1:16", which is technically unstable, yet since the soft point is inherently terminally reliable due to its design and mode of expansion, it expanded evenly. Fired in a 1:9" it would have turned to bird shot in the 1st inch of gel.
Attachments:
lou270
New Member
thetinkerer
No - I am familiar with the article you posted. The
impact to terminal performance and stability is related to fmj bullets and length of narrow channel. I already pointed out that stability has an impact here and there is no dispute. The length of narrow channel in fmj pointed bullets is well understood
As a matter of fact - here is the article that is refenenced in that one - apps.dtic.mil/sti/pdfs/ADA519801.pdf. A less stable bullet in this case caused bullet upset more quickly but that is neither here nor there for expanding hunting bullet. Trying to apply that broadly to other bullets is what I am disputing.
You seem to want to apply Litz’s sg needs to be 1.5 to optimize bc to expanding hunting bullet performance. I have seen no proof other than “it should” that these slight turbulences cause any significant change to expanding bullet performance. Think about it - you are shooting down on the animal or quartering to the animal in the field You are going to have far more change in angle of tip impact than 1 degree you get from a minutely wobbling bullet.
An expanding bullet doesn’t need to be ‘held straight” during penetration by twist. Sorry - but this makes the least sense given how expanding bullets work. The only exception being berger which behaves effecively like a fragmenting fmj design and has neck
However - we can agree to disagree on all this. I am happy to keep discussing it, but I don’t want it to turn negative as these posts do if go too long
One new thing to me is the effect of twist on petaled bullets. I knew something was going on there but could not put my finger on it. The fluting analogy helped
I also think it makes sense that faster twist can increase or at least make bullet expansion easier. Whether that is significant and good or bad thing depends on situation and bullet. I think the bigger effect here is probably seen in bullets designed to fully fragment. In any case probably good idea to follow what the bullet maker recommends in this case and not be shocked if you don’t and bullet doesn’t behave as intended
Lou
lou270
New Member
I am not sure why would want to dismiss the nosler data other than it does not agree with pre-concieved notions. I would say out of everything that is stated on the subject it is most relevant or at least removes the guessing. However I would agree it would be more relevant if there were more data as to bullet type. Based on response and context of article assume an expanding
design (ie do bullets expand more…). Dont really care on range.
As for BC, I would get Litz’s book Ballistic Performance
Of Rifle Bullets. Nosler is not the only one with “intlated BCs” though their 7mms seem about the worst. The 270 and 30 cal not so bad but still high. In any case Nosler is known for terminal performance not BC
Lou
tthetinkerer
Senior Member
Lou270,
I'll try to explain this step by step, because what is intuitive to me may not be to everyone. We KNOW FOR CERTAIN that BC is compromised when a bullet is not comfortably stable*. Why is that? Because pitch/yaw isn't yet brought to its minimum until it is fully stable. This is why I (and bullet manufacturers as a whole who all give minimum twists for theirs bullets) leverage Litz's findings on gyroscopic stability.
A hollow point generally needs to hit the target, drive into it some distance and fill the cavity with some fluid/-like substance which forces it open, and subsequent penetration and drag through tissue completes expansion. If your bullet is pitching/yawing too much at the point of impact it may not hit squarely or open up evenly which does affect terminal performance.
The best thing I can do is to get a second gel block and devise an experiment to show you and everyone how twist can affect terminal performance. Unlike dishonest Nosler, I will use multiple types of bullets with different expansion modes, all fired at the same speed, but in different twists (1:16" vs 1:8").
*full stability actually occurs around 1.4, and not 1.5, but to be safe and to compensate for non-ideal conditions 1.5 is suggested as a minimum
tthetinkerer
Senior Member
Because the Nosler data doesn't say anything about the kind of bullet or the distance. It doesn't really help the discussion about terminal performance of sharp petaled (monolithics). I already know that soft point and JHP style bullets don't care what kind of twist you use as far as their wound channels are concerned, but some modern styles of bullets do. I don't appreciate major MFGs that inflate/lie about BCs to sell their bullets when all they have to do is buy a labradar and be done with it (see attached USAF study).
Now, the Barnes stuff in that article DEFINITELY gives the relevant details and findings that dovetail the gel shots that Farleg showed (which was of Barnes 210gr TSX).
Attachments:
BC comparison.pdf (981.37 KB)
riceman
Global Moderator
Guys to help here i did the twist test in 1 gallon jugs of water.
Rifle used winchester 43 22 hornet 1-16" twist.
35hh 1.1sf. Mv 3100 distance 100yrds. Penatrated and came to rest in 3rd jug.
Only 1 petal came off and bullet tumbled after exiting 1st jug of water.
So decided try 12" twist 223 vanguard. Same speed and distances. 2 petals came off, same 3 jugs but tumbled exiting 2nd jug.
Tried 8" twist 223 ar. Same speed and distance.
Bullet lost 3 petals, 4th broken just never came off. Entered 3rd jug straight but no exit..
Only difference in this test was twist.
This was done 2 years ago.
Attachments:
riceman
Global Moderator
This is a good thread Harperc started a few years ago, may help
lou270
New Member
Thetinkerer
Yep - I get it on the small hollow point. This is a bullet design issue and the reason a big hollow point sits behind the polymer tips of most mono bullets these days. This is long lesson learned mostly with barnes growing pains. As I noted in previous post this is why increased twist can help with small hp. This was part of my point about following manufacturers recommendations.
I will admit I am a bit leary on this concept of small hp since I still believe an angled shot due to elevation or quartering animal will present the hp with a much steeper angle than couple degrees of wobble. What am I missing here. Probably why to this day barnes tsx still has rep of not expanding sometimes though ttsx does not
In any case this discussion turned some from does twist impact terminal performance to does bullet stability impact terminal performance. I am not so interested in this discussion as you noted that most manufacturers supply a min twist. I no way imply that you should use less twist than manufacturer recommends. Assuming you do this bullet will be stable and we are good
One caveat to keep in mind on the sg calculators is that they are approximations. So if litz calculator says 1-8 is stable (sg > 1.5) but hornady says 1-9 that does not mean the calculator is correct and hornady is wrong and you need more twist. The calculators do not take into account the design and density of the bullets (ie real center of gravity). Bullet designers do this when they design bullets. Hornady probably got tired of answering this question from bullet twist calculator jockeys and put out a youtube video
So back to question of twist impacting (assuming bullet is stable) terminal performance of big game bullets. Seems yes to some degree for petal bullets (more twist may make wider but less deep wound - no free lunch) not really for traditonal (ie non-petal) bullets.
Lou
farleg
Platinum Member
GDay the fur calculator is ready, just give him the nod
a lot has been learnt & riceman put up a good thread & a few others have also been chatted over & overwhelming for me is how far we have come & what we’ve learnt just like in this thread it’s fascinating stuff & I personally thank everyone for their input as I’m looking @ things with a bit more or less of a twist
than I once thought of yep just trying to penertrate into the depths with more certainty keep it coming
Cheers
harperc
Global Moderator
And some crayons to explain it to some of us
lou270
New Member
I am basically came to the conclusion of use a bullet that either blows the petals off for collateral damage or use a bullet that expands to front that doesn’t have them. If the consensus is you need faster twist to try and equal the damage why bother unless you just want more penetration and less damage to begin with
Interestingly that is what got me interested in hammers to begin with
Lou
tthetinkerer
Senior Member
Thank you for those pictures, I was always wanted to know what those little 35gr ballistic barrels would look like expanded! That should make an excellent predator bullet...
...no longer any need to buy Ballistic Bob's Beaver Busters anymore!
riceman
Global Moderator
Beaver busters.
farleg
Platinum Member
Gday
Tthetinkerer & lou
I feel like this thread has come to a end for which I kinda agree it’s better if it doesn’t get to long we won’t start rehashing the same points already put forward by you 2
I really really appreciate your time & others probably also
Way above my pay grade but I’ve got a lot out of the discussions by you 2 & paying a little more attention to a few points now really it’s already in the bubble but now it will be way easier to assess so thankyou again
As your fairly new here & If your curious or haven’t already done
Search up “ hammered down under “ thread as it was a great learning curve for me personally on the way hammers were behaving & put a few myths to bed & my mate who guides now uses the 248hh on his house rifle for buff & everything else that gets in the way
Twist to me is ever so important in my choice of pills & yes I like 2 plus of stability but I can live with some pills ( due to preformance) of slightly below 1.5 or around it as it’s just watching the bubble & fur calculator as they don’t lie in my world but I’m yet to see the results of more twist producing lesser results
Gel I’m careful of like other media tests but I really like looking @ it as it gives us great reference points & animal testing will always be king in my world as gel dosent run
Thanks again no offence intended to anyone
& I look forward to more civil discussions like this as it helps so many myself included
Yes this place is awesome
Cheers
lou270
New Member
Farleg
Read through the hammered down post and a coulple of questions/comments.
1 - From what I gather the consensus was that really high sg seemed to work better. Ie shank penetrated more straight vs tumbling
2 - Was the high sg accompanied by higher velocity? For ex, did you see cases where you had less tumbling but still high velocity but a normal sg , say > 1.5 but not super high like 2.5+
From a terminal performance standpoint what twist increases (rpm) is centrifugal force. While twist may not help the bullet deform
it will increase force in a perpendicular direction. So it may make a wider “mushroom” if bullet design allows or if you have weakened jacket for ex it may pull/tear off and get zinged away faster vs stay in 1 piece with a lower rpm. You can see this is varmint bullets for ex
Anothet thing I want to discuss is as I pointed out stability in game and stability in air are very different. flesh is at least 1000 times more dense. So a SG of 1.5 or 4 is big in air but it is .0015 or .004 in flesh. Doesn’t make a difference from a physics point of view (remember - shoulder stabilization). So if you have perfectly straight (>1.5 sg) then more theoretically should not matter. Again field results matter more - so bear with me I have a theory I would like you to think on basis on fur calculation…
Hammers are a but of a different animal in terminal perfomance. They blow the petals off and leave the shank. A normal big game bullet may fragment but in general the bullet mushrooms fairly uniformly out and erodes during penetration.
My theory as why shank penetrates better with increased sg (rpm) is that if you have petals not all tearing off at basically the same time you can create a significant instability in the core which may cause it to either veer off course or even tumble if say one petal stays on for even very small time longer. Increased rpms from higher twist helps the petals come off at same time ensuring no or minimal instabilities are introduced during petal shedding.
Anyway that is one thought that to me is explainable by physics why more twist may help keep the shank straight
. Thoughts?Lou
kneedeep
Full Member
Lou and tinkerer
I don’t have the time right now to join the conversation but have enjoyed reading this discussion. You both make good points and explain them very well.
Lou, I do like your theory above. I hope you explore it more and continue this conversation. I have discussed similar theories on hammers shedding their nose petals and shank stability. Although I did not think about the twist in your theory. Great stuff.
I would like you to think about what the definition of an “expert” is. There are academic experts that understand the physics and can write papers on the subject. But they may not have a full understanding of what’s going on because they don’t have the real world experience to see the hands on results of their writings. Then there are folks like Farleg and others on this forum who have the real world results and observations but may not be able to explain their results regarding the physics. Again why I think Farleg needs to whoa book on terminal performance. And not just with Hammers.
Hope you can combine all the information together.
kneedeep
kneedeep
Full Member
Great post as always riceman!
lou270
New Member
“ I would like you to think about what the definition of an “expert” is. There are academic experts that understand the physics and can write papers on the subject. But they may not have a full understanding of what’s going on because they don’t have the real world experience to see the hands on results of their writings. Then there are folks like Farleg and others on this forum who have the real world results and observations but may not be able to explain their results regarding the physics. Again why I think Farleg needs to whoa book on terminal performance. And not just with Hammers. ”
Agree - absolutely. I have plenty enough of my own experience with non-hammer bullets so the whole extra-emphasis on twist or high sg with hammers has me extra curious. I am not saying twist not important other places but apparenlty extra important here from reported results. I am challenging some of the reasons folks say it helps because it doesn’t jive with well understood iteractions. However, that does not mean, for ex, that I am disagreeing with farlegs results that more twist is better. Just thinking/discussing on what is reasons for it
Lou
kneedeep
Full Member
Lou, I like the way you think.
Some show extremely good results without high SG. Is it an ideally balanced pill (nose/hp/shank) for their velocity and animal resistance? All ,stable, hammers will outperform other designs imo.
Is higher SG a “band aid” to achieve ultimate performance in a pill that’s not ideally balanced for a given velocity and animal resistance?
There certainly doesn’t seem to be a down side to higher SG.
joe16
Platinum Member
Kneedeep
Sir I like the way you think. I think it would be a great read. That's if we could hold Farleg down long enough for him to write a book!!
Tales from Down Under my perspective on bullets and terminal performance. Something like that, but what a great idea!! There's even a few people on here that could give him a hand on some particular sized cartridges. Since he is, you know, narrow in his scope
A book, what a great idea
Joe
lightthetower
Full Member
“Bang, Flop, Calculate the Fur; a Love Story” by farleg
riceman
Global Moderator
"The view from upside down"
farleg
Platinum Member
G'day
you guys are killing me & notes taken on you all ,so sleep with one eye open i say may be advisable lol
Knee-deep now your on the recruitment drive I see hmmmm
Deflection is one I usually don't like but I'll settle for one now lol
I'm not interested in writing a book , man I haven't got enough time in the day now but I would gladly add a forward or whatever its called to a book if Steve ever does one & if he would even consider me to put something in it I would be honoured if that was the case
kneedeep so time you get onto Steve if you want me to put pen to paper lol as that's the only way I'd do it howz that for a deflection , I'd say a pretty good scapegoat
I'll keep one finger typing here while trying to get past spellcheck also as this place is my book I am humbled by the suggestion that I could write a book & appreciate all that you guys do for me as its way more than I can ever give
You guys are simply the best in so many ways
Now its back to the topic & my book lol
Cheers
farleg
Platinum Member
Gday lou & others please chime in & pull me apart
lou to answer your questions
1/ yes
2/ overall the greatest indicator was a higher sh showed a very consistent outcome regardless of velocity with no tumbling or minimal
as we got to the lower sg you could see a pattern of tumbling occurring ( most people will never see this as critter size the shanks gone before it would start ) on a more regular basis
from a terminal preformance standpoint::
I get a given twist flings off the petals due to more tork ( I may be wrong on my wording so please correct me ) & I was really worried going to a 7 twist in my 375 but I’ve been pleasantly surprised ( phew ) but I had to see actuals not theories, I’m better @ putting it in practice than a theory side as it’s so clear once I see the insides of a animal & reaction to the shot vrs me trying to assume on theory base
( guess that’s also just experience over many 100”s thousands of critters? Or ? But I do believe I’ve got a knack @ seeing what’s going on really quick & my mates have told me this many times over the years ( I’m trying not to come across as cocky so please don’t take it that way )
the zinged away faster if I’m reading this correct
a few of us have come to look @a petal /shank ratio that is showing in the same twist you get the ratio correct & the shank penetrates not just penertrates it does so @ a higher velocity & goes deeper ( parachute effect )
this to me goes with what you & tthetinkerer were on about in proper terminology so accept my apology for my hack version & just hope you can follow what I’m saying & I’ll also add this if you get this correct the tumbles @ the end isn’t as pronounced & it’s not just getting the petals out the way asap as more terminally to it than just that as other brands haven’t got it yet or maybe I haven’t but runs on the board go to hammers & this subtle difference is it I think
air & flesh stability : totally Agee they are majorly different resistances & even in same critter placement also big bones come into it ( higher sh is king here I believe)
& got you on hammers are different & even though other brands try to replicate they haven’t ( actually hammers perfected a system all ready done by others )
im ticking on your theory & got no right to dispute physics but it is also a little put up above that physics may suggest we have stumbled onto a easier quicker ride
Just above my pay grade then we get the bubble & how does that work as we get a massive smack like a frangible ( too higher velocities & fast twist ) but with the penertration of a wad cutter with a bigger wound channel all the way till it stops ( if you catch it ) but does lesson as it gets closer to its final resting place
now that’s on bubbles that go sideways you get the bubble correct ( help kneedeep what’s that direction explosive charge called again) & watch the magic happen & to me I’m leaning towards a higher sh than we once thought as I’ve seen no preformance issues & potentially iron out any shoulder stabilise issues that may show up especially on bone
( triangles parameters still number 1 )
no doubt I’m a spear freak as from my results nothing can match it on consistency ( if the pills capable ) but I’m also not worried with a low impact velocity as this is where hammers really shine over all other monos & a fair few frangible/c&c
( I can see the eyes rolling in a few heads now lol )
but penertration is the one that will ultimately get the most consistent results day after day year after year well it has in my world
shoulder stabilisation is critical in slower twists & im leaning towards a shank length to caliber ratio that may have no peers ( I’ve mentioned this a long time ago but no takers so anyone this time round
) speed of shank is also important & isn’t just the highest impact velocity achievable
the biggest thing I’ve taken on board is in the transitional zone & thank you & tthetinkerer so much for your discussion & you don’t know how much this has helped me on the picture I now see in my thought process
so thanks guys ( everyone) it’s the most wonderful conversation no right nor wrong it’s all learning/ teaching as that’s what you’ve done for me
now go pull me apart as that’s how we learn
& lastly you can put that in your book when you write it up kneedeep
cheers
no proof read sorry
tthetinkerer
Senior Member
Gentleman, specifically Farleg and lou270,
I found this the other day, and I think it is testing done in a crime lab under controlled conditions. It demonstrates that better stability factor will create deeper penetration before tumble, which is something that many here, including the designer of these bullets, have witnessed in viro (higher speed all things equal = slightly higher SG; tighter twist all things equal = much higher SG):
www.shootingtimes.com/editorial/handgun-bullet-stability/389036
The technician uses FMJ bullets which, like a Hammer shank, do not have a stabilizing shoulder. You will read how they test the very theory we were discussing in a limited fashion, and how the higher SG penetrates deeper without tumbling.
I know the physics says that the difference shouldn't matter in a much denser media, but it's like I said, I think the difference between higher and lower SG is set in motion at the point of contact before the physics of the more dense media is dominant.
Great discussion, guys. Seriously.
PS
We should name farleg's book "getting hammered: memoires of a self-proclaimed muppet"
farleg
Platinum Member
Sep 2, 2022 at 4:55pm tthetinkerer, lou270, and 1 more like thisQuoteEditlikePost OptionsPost by farleg on Sep 2, 2022 at 4:55pm
tthetinkerer Avatar
Sep 2, 2022 at 9:52am tthetinkerer said:
Gentleman, specifically Farleg and lou270,
I found this the other day, and I think it is testing done in a crime lab under controlled conditions. It demonstrates that better stability factor will create deeper penetration before tumble, which is something that many here, including the designer of these bullets, have witnessed in viro (higher speed all things equal = slightly higher SG; tighter twist all things equal = much higher SG):
www.shootingtimes.com/editorial/handgun-bullet-stability/389036
The technician uses FMJ bullets which, like a Hammer shank, do not have a stabilizing shoulder. You will read how they test the very theory we were discussing in a limited fashion, and how the higher SG penetrates deeper without tumbling.
I know the physics says that the difference shouldn't matter in a much denser media, but it's like I said, I think the difference between higher and lower SG is set in motion at the point of contact before the physics of the more dense media is dominant.
Great discussion, guys. Seriously.
PS
We should name farleg's book "getting hammered: memoires of a self-proclaimed muppet"
Gday tthetinkerer
thanks for the link I’ll read it as soon as I get time & I hope you can interpret my writing as I struggle myself sometimes as what my heads thinks then I don’t no how to spell a word ( spell check is frustrating for me sometimes) so I replace it with others that are hopefully correct or sometimes the sentences just don’t flow
so I guess that leads us into the ps
oh so your on the bandwagon now lol but I will say that’s pretty cool
thanks to everyone who contributes no matter how small it make this place awesome & the place I love
cheers
kneedeep
Full Member
I have to make this extremely quick, so you'll can hash it out one way or another. This thought process came from my start with percussion cap muzzleloaders. Large, low bc bullets, low velocity, 20 twist plus barrels and then wadcutters.
A stand out pill 308 124HH
Standard stability above
308 124 shank stability below
Above, assuming the shank retained 60% of it's velocity after shedding nose petals.
Shank bc estimated from a wadcutter similar to in size to the shank, below
Below is shank with increased twist.
Throw in lou270 shoulder stability on top of increased stability after tthetinkerer "transition zone" and I believe we can see where the physics start to play in our favor with increase twist for shank. No time to go into more details. Please run the numbers for yourself and make sure there are no mistakes here. I also believe there is a big difference between "stable" bullet in it's ballistic form and a "stable" shank (wadcutter) in it's terminal form. You did a great job of explaining that tinker. I also believe if the shank has FOC (forward of center) balance, there is increased benefit there. A bullet in it's ballistic or terminal form is rotating around it's center of gravity. Where this center of gravity is located makes a difference on whether or not it wants to move front first or tumble.
I also have a crayon drawing in mind to show some of this but no time to make them up.
farleg - "shaped charge" focuses the energy right where we want it. And boy did you get me to come full circle on that topic!
No time for proof read or further explanation. Please use a Tasmanian translator for this one
kneedeep
joe16
Platinum Member
Kneedeep
Very nice thought process, well put together. You'll have us scratching our heads for a few hours (how did HE come up with that??) before any replies I'm sure. Nice job, Birds must be flying good!!
This place is awesome
Joe
