mrdinapoli
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Posts: 25 | Jan 31, 2023 at 12:58pm gltaylor, farleg, and 3 more like this
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Post by mrdinapoli on Jan 31, 2023 at 12:58pmkneedeep,
I almost got a chance to try my loads yesterday — had the day off and weather was beautiful. I returned from a meeting, and my wife had company over. Since my range is 50 yds off my back door, I was vetoed. So hopefully soon.
Trying to get caught up on all the discussion, so here are several thoughts/comments:
1. I just saw a post on “setting neck tension with a mandrel as the last step” on LRH that looks good. I did take a quick look and saw a post regarding neck tension possibly not being the main issue, as bullet release is largely controlled by neck expansion from powder expansion. However, the initial build up of pressure will still be controlled by neck tension, contact with lands, etc, as we discussed before. So food for thought. Alex Wheeler and several other well versed reloaders have posted. It is 9 pages long, and I have not had time to look thru it much, but keep it in mind. (https://www.longrangehunting.com/threads/mandrel-as-last-step.258463/page-9)
2. Erik Cortina and other professional shooters have suggested that from their testing and experience, CONSISTENT NECK TENSION IS MORE IMPORTANT THAN THE ACTUAL AMOUNT OF NECK TENSION. I agree with this statement and this is one of the reasons why I set my final NT with mandrels. This may be due to and also further support the supposition that neck reduction and then upsizing with bullets or mandrels reaches a point of plastic deformation of the brass necks, after which point further neck tension due to the elasticity of the brass can not be obtained.
3. I did check my supplies at hand and their ability to fit together. I have bases for arbor presses that have a built in center bore to collect primers (in case used for depriving), that are large enough to pass a 6mm bullet, but not the case neck. However, they will allow a loaded 22 cal case neck to pass. This means that I should be able to use the process and design mentioned in earlier post to test bullet pressure release on my 6mm CM and 22 CM without needing to have something custom made. In addition, I do have bushings for my 6mm CM at home to allow neck tension settings of 0.001” to 0.006” after allowing for 0.001” spring back. I do not have mandrels for all these sizes, so NT will need to be set by neck bushing and then expansion will be achieved by bullet seating. However, it should enable me to at least address the question: “do you reach a point in neck reduction at which neck re-expansion with a bullet (or mandrel) causes enough plastic deformation of the neck, that a fixed elastic tension is reached; after which point further neck reduction only increases brass working and does not add additional tension.” I have some already fired cases sitting around, and I will see if I can test this when I get a chance. It will also be interesting to see the differences between bullet release pressure for standard cup and core bullets vs hammers. There are 2 main factors that I see may play a role: 1) there is an overall reduction in surface contact area with the Hammers where the driving band peaks contact the case neck; however, 2) the neck can be seen actually “sinking’ into the intervening valleys between the driving band peaks due to the elasticity of the brass. Movement of the bullet will need to upsize or overcome these reduced intervening areas prior to movement. The exact balance or trade off between the two will be interesting to see in testing.
4. One other thought regarding neck interaction with the driving bands of the Hammers: I image one must use caution seating bullets consistently into the neck to get the most consistent results. ie. it might be best to have the bullet seated to a point where 3 things occur: 1) the same number of driving bands are seated within the parallel walls of the case neck — this should be obvious, but probably most important; 2) the bullet should be seated to a consistent depth where the case neck mouth ends up in the middle of the valley between 2 adjacent driving bands — if it is seated where the mouth is on the top of one of bands, small inconsistencies (even 0.001”) in seating depth may affect release pressure — more pressure if the mouth is in front of the band, and less if it is behind; 3) the last driving band should be seated in a consistent position in relation to the case neck/shoulder junction — this will likely be controlled by 1 & 2, as well as keeping case base to datum measurements consistent.
5. In response to your questions about my reloading and load work-up process, you are correct: 3 rounds each of each powder charge x 4 charges, for each type of bullet and for each powder. I have always done this in the past because I like to see group sizes for each charge. The problem is that this really adds up, and I don’t like to shoot a lot of rounds thru my hunting rifles. I have read in the past, and have been rereading about OCW and OBT testing to get the overall best and most stable results, including with variations in temperature and slight variations in powder charge and bullet distance to lands with reloading variation. However, many of these still use 3 shot groups.
I really like the method you described with the Hammer bullets — choosing 1 powder and using 1 round each for each charge shot into one group, and then analyzing overall group size. It is really interesting that you mentioned that 1 powder will often shoot much better than the others. Then you can pursue that powder further. In addition to showing overall group size attributed to the powder itself, this would allow for observations in vertical and horizontal dispersion of the shots with that particular powder to provide info about the harmonics and pressure/shock wave node in relation to bullet release timing. In theory, this would address all the topics at one time with the least amount of shots and components. It would address: “powder preference” for bullet in that particular barrel, OCW (barrel vibration and harmonics), and OBT (barrel shock wave/pressure node).
Many of these likely overlap, and when we say that a barrel “likes” a particular powder better than other powders, it is likely because the powder, bullet, barrel, harmonics, pressure node, etc, all fall into the best alignment and widest tolerances for that particular barrel, bullet, and powder. Your method appears that it is a quick way to sort through the best candidates so you can discard the poor candidates. From there, it can be fine tuned further. It may be possible that on occasion a better combination will be able to found with firing many 3 shot groups, but this would likely be the exception rather than the rule. In fact, needing to shoot many groups in my method is what prevents me from trying different powders and combinations. I choose several loads from what appear to work for others, test them, choose the best, and ignore all the other possible combinations.
I WILL BE TRYING YOUR METHOD AFTER I TEST MY CURRENTLY LOADED ROUNDS.
6. As mentioned in my answer to Joe16, I have never considered crimping because I have always followed BR, F-Class, Hi-Power, PRS, and ELR loading methods, which do not use crimping. However, it has come up often enough that I will need to look further into it. After I shoot my loaded rounds and see how they perform, I may need to try crimping a few successful combinations to see the effect on accuracy and velocity. I will likely need to move my testing over to my 6CM or 6.5x47 which have heavier barrels and burn less powder and components. I am always open to new ideas and testing.
This is a picture of what I described in my earlier post to testing bullet release pressure.
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and others I went straight to a half.
