350 Legend Load Development, Crimping?

BuckeyeHntr

BuckeyeHntr

Well-known member
I have a load developed for this rifle that shoots at 1” and occasionally under. With a 125 gr Shock Hammer I am attaining an average of 2800 fps. Out of a CVA scout with a straight wall cartridge I feel these are good numbers.
My question is, is this a round that should be crimped? As it headspace’s on the cartridge mouth and is sensitive to case length my gut says “no it should not be crimped”. Thought I would pick the brains of the folks roun’ here.

OH….
 
Depends on how much neck tension and or how far into the case the bullet is seated.
Ideally it's best to crimp for semi auto..
 
I am running a single shot rifle so I am not concerned about “set back”. I am looking as most are on this site about using a crimp to tune accuracy and velocity. My concern is that if crimped the round will have nothing to headspace on as it is rimless and headspace’s on the mouth of the case, causing the cartridge to drop too far into the chamber. Thanks for the reply’s all!
 
BuckeyeHntr said:
I am running a single shot rifle so I am not concerned about “set back”. I am looking as most are on this site about using a crimp to tune accuracy and velocity. My concern is that if crimped the round will have nothing to headspace on as it is rimless and headspace’s on the mouth of the case, causing the cartridge to drop too far into the chamber. Thanks for the reply’s all!
Click to expand...
If I recall rounds that headspace off the rim can only be crimped with a taper crimp. I can't remember... maybe worth a web search.
But if I was loading this for a single shot I would start without crimping and see what accuracy is before I worry about improving group size. Hammers tend to be easy to get good groups from the start.
 
Outdoor Edventure, that is a good looking round. What is it? I’m worried that a crimp into the bottom of a PDR band would not allow the cartridge to headspace properly.
Koda, I believe you are correct on cartridge’s that headspace off the rim.
 
BuckeyeHntr said:
I’m worried that a crimp into the bottom of a PDR band would not allow the cartridge to headspace properly.
Click to expand...
I agree that's a legit concern.
You could try crimping on top of a band... (it might move the seating depth)

I would start with no crimp. I have 2 Hammer recipes that get great groups without a crimp so I'd start with none and see what you get first.
 
The groups and velocities I mentioned were shot without a crimp. Just trying to find out if one is feasible. I suppose I could try a light crimp on the top of a PDR band as you suggested. That makes more sense.
 
Sorry all, I’m in Colorado at the moment.

@BuckeyeHntr you are wise to understand and foresee the issues regarding crimping Hammers in the 350 legend. I understood the issue when I started loading the 350 but I still had an extreme over pressure from the case mouth getting pinched in the mouth of the throat. I don’t have the pictures and information on my phone. I’ll try to pull some pictures off of some past text messages.

Kneedeep
 
IMG_4167.jpeg
You can see where the case mouth is stretched on the right side.

This happened in a cheap AR upper with starting load of LilGun. I’ll try to look up the details when I get home and get some time.

Kneedeep
 
I don’t think that the failure above was crimped. I’ll have to check my notes.

In an email exchange with hodgdon they explained that the 350 legend was designed to be taper crimped. They further explained it needed to be crimped because of the type of powder and amount of case fill used. If not crimped, the bullet can move forward, from primer ignition, into the lands as the powder fully ignites. This can cause high pressure.

Will crimping hammers on top of a PDR band work? I don’t know. When I crimped a hammer on top of the PDR band, it appeared to deform the brass rather than the copper. I am very skeptical about crimping hammers in a PDR valley for the same reason you are @BuckeyeHntr

350 legend chamber warning.jpeg
Here are some comparisons i made. It is difficult for me to accurately measure the case mouth after loading, so take the measurements with a grain of salt.

Kneedeep
 
Have you considered seating it to shoulder and crimp it there? The 125’s is less than an inch long, which will still give you adequate powder capacity for 350 Legend Distances.
 
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Ed

I’ll get details when I get home. I’m pretty sure I had the 172sh loaded to the shoulder. I never fired a hammer in the 350 that was crimped in the PDR valley. I only loaded a dummy round that was crimped in the valley to measure the effect.

I think this failure was from a combination of issues. Trim length, possible sloppy chamber job and a metal chip that was stuck at the lip where the case mouth headspaced. I had cleaned the barrel before firing the first shot through it. But I didn’t buy a borescope until I locked this one up. I found the metal chip after I had cleaned it after the over pressure.

I have loads for a CVA scout and ruger American with no issues. They are however loaded with the 165 flex tip. Every good accuracy and velocity.

Snapseed.jpeg

Kneedeep
 
kneedeep said:
I don’t think that the failure above was crimped. I’ll have to check my notes.

In an email exchange with hodgdon they explained that the 350 legend was designed to be taper crimped. They further explained it needed to be crimped because of the type of powder and amount of case fill used. If not crimped, the bullet can move forward, from primer ignition, into the lands as the powder fully ignites. This can cause high pressure.

Will crimping hammers on top of a PDR band work? I don’t know. When I crimped a hammer on top of the PDR band, it appeared to deform the brass rather than the copper. I am very skeptical about crimping hammers in a PDR valley for the same reason you are @BuckeyeHntr

View attachment 2112
Here are some comparisons i made. It is difficult for me to accurately measure the case mouth after loading, so take the measurements with a grain of salt.

Kneedeep
Click to expand...
Thank you for the info kneedeep. So far I have only seen some unexplained flat primers. Nothing like you have experienced. My best results have been with no crimp and the 125 SH’s seated with the case mouth landing in the middle of a of a convex drive band (the finite part the gets engraved on a hammer). In my caveman brain this made the most sense. Put the case mouth on the bearing surface of the bullet without a crimp and it should headspace, right? It has so far.

OutdoorEdventure,
I hadn’t considered that as I am already close to compressed load of W296 if I seat the bullet any deeper…. Yikes. But it would be something to try to see if accuracy improves!

OH…
 
BuckeyeHntr said:
Thank you for the info kneedeep. So far I have only seen some unexplained flat primers. Nothing like you have experienced. My best results have been with no crimp and the 125 SH’s seated with the case mouth landing in the middle of a of a convex drive band (the finite part the gets engraved on a hammer). In my caveman brain this made the most sense. Put the case mouth on the bearing surface of the bullet without a crimp and it should headspace, right? It has so far.
Click to expand...
BuckeyeHntr

Your theory is sound regarding the case mouth on top of the PDR band. You can measure your loaded case mouth to see what the diameter is. I don't believe it's too difficult to measure the uncrimped case mouth. But I believe measuring the case mouth on taper crimp is difficult to measure accurately.
350 legend cartridge spec.png
The case mouth dimension is .3780" (-.008") so .3780" to .3700"

A heavy crimp in the valley of the PDR band can produce a case mouth diameter under .3700" (see earlier post .3670"). With that said, knowing what I know now, I will not load a 350 Legend (or similar cartridge) without crimping. Your random flat primers are likely coming from the bullet getting pushed into the lands from the primer ignition, as the main powder charge ignites.

I recently tried to taper crimp a dummy round on top of a PDR band. I was unsuccessful as the crimp moved the seating depth every time. So I don't think you can really just crimp on top of a PDR band. The copper is too hard to allow the brass to press into it so in my mind the case mouth has to roll over the PDR band to some extent in order to crimp. Evident by my seating depth getting changed each time. So each to their own on whether or not to crimp and or where to crimp. I'd just suggest being careful and measure your case mouth.

The 350 Legend is a very finicky cartridge to load, in my opinion. I believe it is very unforgiving. I also contacted @joe16 during this process to get some advice on loading straight wall cartridges. In the end, everything seems to make a difference with this cartridge. As an example (using the same powder charge, OAL and crimp) just switching primers resulted in 122fps loss in velocity. And it was a consistent loss in velocity. Other primers were around 50 fps difference.

Good luck
kneedeep
 
I will also add to watch your case trim length. I took an empty, trimmed and prepped case and to the best of my ability scored a .010" mark on the inside of the case mouth. I then put this case into the chamber of the rifle that had the overpressure. I ran my borescope down the barrel and took a picture of the chamber and case mouth. I then used my photo editing software to crudely measure (based off my scored mark) the distance between the case mouth and chamber lip. The gap looked to be excessively long (longer than saami spec). I believe this could have been part of the reason for my overpressure. I now only trim .005" off of saami max case length instead of the standard trim to length, just as a precautionary measure.

The 350 saami chamber spec was revised to shorten the chamber dimension due to pressure problems with factory ammo after it was first released onto the market. See saami website for revision.

I will also advise everyone to think about chamfering the case mouth. Inside and out. I personally chamfer inside slightly but only try to remove the bur (if there is one from trimming) on the outside of the case mouth. I believe excessive chamfering in combination with other factors can lead to issues and inconsistencies.

Regards
kneedeep
 
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