Researchers slant data all the time.
Myth Busting Neck Tension and Bullet Setback
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fxvr5
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Data or Day Ta is only meaningful if it means something,and the results can be used. Just like statictics. The researcher can pretty much make the results come out how ever they want by the sample size.
Show your evidence.
Thread drift: For anyone interested in what has become one of the most common/pernicious sources of false results (particularly in the social sciences) that does not require any outright falsification, check out 538's p-hacking tool. Warning: stat nerd stuff, only bother with this if you care about stats: https://fivethirtyeight.com/features/science-isnt-broken/#part1
Outright falsification of data/direct measurements is pretty rare, and generally subject to severe sanction in academia when it is discovered.
There are other sleight-of-hand tricks that researchers often play... and usually they begin by fooling themselves.
The data provides some interesting insights, however the sample is much too small to draw any conclusions. In post 9 many of the samples that were tested more extensively did not experience any setback. It is possible the original pool of brass that didn't have setback would have experienced setback with other pieces of brass. Look at the GFL and PMC brass - most pieces in the second test did not setback yet they are labeled as suspect brass because they didn't pass the first test.
Additionally die tolerances are all over the place. One die / brass combo might work perfectly, while someone else with the same manufacturer die set might have different tolerances. I have 3 sets of 38 special dies. The sizers all have different diameters - .373, .375, and .376.
If you had a team of 10 people perform the test with their various pieces of reloading equipment and their stash of brass and the results all produced a similar outcome you would be able to start drawing some conclusions.
Additionally die tolerances are all over the place. One die / brass combo might work perfectly, while someone else with the same manufacturer die set might have different tolerances. I have 3 sets of 38 special dies. The sizers all have different diameters - .373, .375, and .376.
If you had a team of 10 people perform the test with their various pieces of reloading equipment and their stash of brass and the results all produced a similar outcome you would be able to start drawing some conclusions.
vaalpens
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Even though you are skeptical about the test results due to sample size and all the other variables, I think at least you can agree that Blazer and FC brass did not perform well in the sample we have seen so far. What would help is if you can independently perform you own setback test to add to the sample size, and increase the validity of the findings.
OP
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LiveLife
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Wow! Thank you for all the responses and valid counterpoints (Point taken and disclaimers put in the OP) - https://www.thehighroad.org/index.p...sion-and-bullet-setback.830072/#post-10711217
I added how I verified the accuracy of the calipers to the OP.
Now, let's get back to the OP goal of myth confirming or busting "Neck Tension and Bullet Setback".
Vermont Gage Class ZZ pin gage as verified on this thread - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10523549
I added how I verified the accuracy of the calipers to the OP.
Now, let's get back to the OP goal of myth confirming or busting "Neck Tension and Bullet Setback".
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more info on varying neck tension of mixed 45acp cases:
i just grabbed my bucket of sized cases and started measuring case mouth thickness. pmc cases have a problem here. everything else varies no more than .002" individually and all "good" cases measure .009"-.011", or .010"-.012", or better.
the "good" mix included: herters, federal, winchester, r-p, cbc, f.c., aguila, pmc and various military cases. the "fail" group was almost all pmc. the thin group is pmc and a military case.
fyi,
murf
i just grabbed my bucket of sized cases and started measuring case mouth thickness. pmc cases have a problem here. everything else varies no more than .002" individually and all "good" cases measure .009"-.011", or .010"-.012", or better.
the "good" mix included: herters, federal, winchester, r-p, cbc, f.c., aguila, pmc and various military cases. the "fail" group was almost all pmc. the thin group is pmc and a military case.
fyi,
murf
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LiveLife
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No, range testing will be conducted as mentioned in post #9 - https://www.thehighroad.org/index.p...sion-and-bullet-setback.830072/#post-10710859
As to the range testing methods, same as how I have done other load developments and powder work ups on THR:
- 17" Just Right carbine (9/40/45 caliber conversions) with 1:16 barrel twist rate and/or 16" PSA carbines with 1:10 barrel twist rate
- 10 shot groups at 25 yards
- Caldwell chrono with Android app
We have just begun to confirm or bust the myth of "Neck Tension and Bullet Setback" as my measurements started with X-Treme 100 gr RNFP sized .355" with short bullet base (This was done intentionally to exaggerate bullet setback).
As a prelude to "Mother Of All Bullets" thread, I plan to test other bullets of different types (Jacketed/Plated/Coated Lead/Lead) and sizing (.355", .3555", .356").
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Wis-Harpo
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What would the results be if you loaded a magazine of loaded rounds and the last round was a dummy. Then shot all of the loaded rounds, and chambered the dummy like what occurs during normal cycling . What would be the setback of the dummy round due to the recoil of the loaded rounds and normal cycling? This is easy to put into print, but time consuming in practice. This is a question not a comment to any other post. I was just wondering and want to learn a thing or three.
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LiveLife
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Wis-Harpo, good question.
Methods we use to test our finished rounds should be subjected to same/similar actions/forces our pistols generate. That's why I stopped pushing on the bullet nose against the bench top to check neck tension rather I now feed/chamber the rounds from the magazine and release the slide without riding it, which better duplicates the actions and impact forces the bullet nose/case neck experience during actual firing.
I could include the last dummy round in the magazine for the range test to see if the bullet setback results duplicate my current test of releasing the slide without riding it.
vaalpens, thanks for case wall thickness data on post #25 - https://www.thehighroad.org/index.p...sion-and-bullet-setback.830072/#post-10711217
murf, thanks for the case wall thickness data on post #34 - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-2#post-10711334
Before I started this thread, I was actually preparing a myth busting thread for case wall thickness. What I didn't realize was there were variables I did not factor that could overshadow other variables to produce neck tension and subsequent bullet setback if neck tension was insufficient:
I will add portions of this post to the OP.
Next, I will measure bullet setback using different sized bullets ranging from .355" to .356".
Methods we use to test our finished rounds should be subjected to same/similar actions/forces our pistols generate. That's why I stopped pushing on the bullet nose against the bench top to check neck tension rather I now feed/chamber the rounds from the magazine and release the slide without riding it, which better duplicates the actions and impact forces the bullet nose/case neck experience during actual firing.
I could include the last dummy round in the magazine for the range test to see if the bullet setback results duplicate my current test of releasing the slide without riding it.
vaalpens, thanks for case wall thickness data on post #25 - https://www.thehighroad.org/index.p...sion-and-bullet-setback.830072/#post-10711217
murf, thanks for the case wall thickness data on post #34 - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-2#post-10711334
Before I started this thread, I was actually preparing a myth busting thread for case wall thickness. What I didn't realize was there were variables I did not factor that could overshadow other variables to produce neck tension and subsequent bullet setback if neck tension was insufficient:
- While most of us focus on case wall thickness near case mouth (.010"-.012" average thickness), this is NOT where most of friction with bullet occurs to establish neck tension.
- To me, most of neck tension occurs below case mouth likely near mid point of bullet to bullet base where case wall thickens much more than at case mouth.
- This is why taper crimp plays a very small part in increasing neck tension as taper crimp is usually applied near case mouth.
- When neck tension/significant bullet setback issue is posted, we often suggest to ensure the brass is full-length resized and/or to use smaller expander/flare which reduces the ID/OD of case neck below the case mouth.
- And this was the biggest realization - Depending on headstamp, case wall thickness varied at different points around the case mouth and multiple measurements were needed.
- Yes, case wall thickness is not often consistent. Some headstamp vary with less than .001" but some others vary with over .002" and this explains why some loaded rounds have out-of-round case neck.
- I initially took 4 measurements around each case mouth at 12/3/6/9 O'clock and found case wall thickness on the same case could vary up to .001"-.002" which significantly affected case wall thickness measurements since typical case wall thickness measured .010"-.012" on average (.002" range).
I will add portions of this post to the OP.
Next, I will measure bullet setback using different sized bullets ranging from .355" to .356".
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not to beat a dead horse, but i did want to give pmc a fair chance. i sorted out my pmc fired cases and measured again:
some of these have been reloaded a number of times, a lot are once fired cases. the "fail" cases are at least a .003" variance. the "ok" cases have a max. of .002" variance.
i guess the next step is to load up the two groups, run them through the chrony, punch some paper and see what happens.
for now, i'm not going to include pmc 45acp cases in my "mixed" pile.
murf
p.s. this falls under the "neck tension" catagory!
some of these have been reloaded a number of times, a lot are once fired cases. the "fail" cases are at least a .003" variance. the "ok" cases have a max. of .002" variance.
i guess the next step is to load up the two groups, run them through the chrony, punch some paper and see what happens.
for now, i'm not going to include pmc 45acp cases in my "mixed" pile.
murf
p.s. this falls under the "neck tension" catagory!
Toprudder
Member
Good info, BDS.
I'm not the least surprised that different headstamps would have differences in neck tension. Some time ago, just out of my own curiosity, I inspected and measured different 9mm headstamps (over a dozen) and saw significant differences in wall thicknesses and taper. The majority of the cases had constant wall thickness from the case mouth down to about 0.200", then the wall thickness started to increase all the way to the web. There was a least one headstamp (Hornady?) that tapered in thickness starting immediately at the mouth. And then there were the headstamps with the internal "step" (IMT, FM, Ammoload) that had a constant thickness from the mouth to the step.
One thing I took away from this is that some cases are more suited for 147gn bullets, and some are more suited for 115gn (or lighter).
I'm not the least surprised that different headstamps would have differences in neck tension. Some time ago, just out of my own curiosity, I inspected and measured different 9mm headstamps (over a dozen) and saw significant differences in wall thicknesses and taper. The majority of the cases had constant wall thickness from the case mouth down to about 0.200", then the wall thickness started to increase all the way to the web. There was a least one headstamp (Hornady?) that tapered in thickness starting immediately at the mouth. And then there were the headstamps with the internal "step" (IMT, FM, Ammoload) that had a constant thickness from the mouth to the step.
One thing I took away from this is that some cases are more suited for 147gn bullets, and some are more suited for 115gn (or lighter).
you might want to look at the spreadsheet in post #12. i did a bit of measuring on just this subject a few years ago. i reached the same conclusions as you.
murf
fxvr5
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You might want to measure their length as well. Bullseye shooters are pretty sure case length matters as it contributes to headspace which is known to affect accuracy.
45 auto cases shorten the more they are fired. http://massreloading.com/loading45ACP.html
You don't want to make the wrong conclusion, i.e. that neck tension affects accuracy, when the actual variable that affected accuracy was case length.
i don't know which post you are commenting on, but i always try to eliminate all variables save the variable i'm testing when i do a test. these cases will get my normal prep which includes checking case length.
murf
fxvr5
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sort them for long and short.
longer cases fit better = less loose headspace = better accuracy because they fit the chamber more consistently.
OP
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LiveLife
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murf, thank you for the additional data.
I had one experience with PMC 45ACP brass that may be pertinent. One day at the range, I noticed a bunch of shiny brass on the floor. When I checked, they were PMC. When I tested different factory ammunition for USPSA matches, PMC and S&B were ones that produced smaller shot groups among other brands and I used them for matches until I started reloading (BTW, reloads shrank my groups by 40%).
When I got home and after tumbling the range brass, I ran into failure to fully chamber issues with PMC brass I had just picked up from the range floor. After some investigation, it turned out this particular lot of PMC brass was softer and was collapsing during bullet seating just enough to bulge the brass and hang up with the chamber wall.
I reloaded other PMC brass I had and could not reproduce the problem. I also did not experience any problem with other 45ACP brass I picked up from the range floor. I culled the entire lot of PMC 45ACP brass I picked up from the range floor and tossed them in the recycle bin.
This demonstrated to me posts other THR members made about lot-to-lot variance in brass quality and condition. These were obviously new brass once-fired that day, yet brass quality and condition were such that they weren't suitable for reloadng.
Other thing for me to add about PMC brass is that I have a Lone Wolf 40-9 conversion barrel with tighter chamber and no leade (Like my Sig 1911 barrel) that requires taper crimp die adjustment to fully chamber rounds compared to other headstamp brass (NOTE: These rounds will fully chamber in other barrels like KKM, Lone Wolf and factory). I have similar issue with CBC, GFL and newer R-P headstamp brass.
When I measured the case wall thickness at CASE MOUTH, the headstamp cases that did not fully chamber did have slightly thicker case walls but not always (That's how I found the inconsistency of case wall thickness on the same case). So it was out-of-round finished rounds that were causing the failure to fully chamber ... so I thought. When I adjusted the taper crimp die so measurement at case mouth was .378" (.380"+ will not chamber in the tight chamber Lone Wolf barre with no leade) with not out-of-round rounds, the rounds still did not fully chamber. That's when I realized failure to fully chamber was caused by bulging of CASE NECK below the case mouth, particularly near bullet base where taper crimp die won't reach.
So, it is not just the case wall thickness at case mouth we need to focus on but the case wall thickness near bullet base. I could use the Lee FCD to "fix" these rounds so they would fully chamber but that's not the focus of this thread.
Of course, measuring case wall thickness at bullet base seating depth is not easy as resized case length varies and finished OAL varies which in turn will vary the bullet seating depth ... so no measuring of case wall thickness at bullet base seating depth.
That's why I started this "Neck Tension and Bullet Setback" thread instead as measuring bullet setback is easier and factors in other variables.
I know. I know. I can already hear the keyboards clicking away to point out the variables of variables but I figured, this is one data set I can use for the "Mother Of All Bullets" thread. I can already see that I will end up using a particular headstamp cases with specified resized case length.
I had one experience with PMC 45ACP brass that may be pertinent. One day at the range, I noticed a bunch of shiny brass on the floor. When I checked, they were PMC. When I tested different factory ammunition for USPSA matches, PMC and S&B were ones that produced smaller shot groups among other brands and I used them for matches until I started reloading (BTW, reloads shrank my groups by 40%).
When I got home and after tumbling the range brass, I ran into failure to fully chamber issues with PMC brass I had just picked up from the range floor. After some investigation, it turned out this particular lot of PMC brass was softer and was collapsing during bullet seating just enough to bulge the brass and hang up with the chamber wall.
I reloaded other PMC brass I had and could not reproduce the problem. I also did not experience any problem with other 45ACP brass I picked up from the range floor. I culled the entire lot of PMC 45ACP brass I picked up from the range floor and tossed them in the recycle bin.
This demonstrated to me posts other THR members made about lot-to-lot variance in brass quality and condition. These were obviously new brass once-fired that day, yet brass quality and condition were such that they weren't suitable for reloadng.
Other thing for me to add about PMC brass is that I have a Lone Wolf 40-9 conversion barrel with tighter chamber and no leade (Like my Sig 1911 barrel) that requires taper crimp die adjustment to fully chamber rounds compared to other headstamp brass (NOTE: These rounds will fully chamber in other barrels like KKM, Lone Wolf and factory). I have similar issue with CBC, GFL and newer R-P headstamp brass.
When I measured the case wall thickness at CASE MOUTH, the headstamp cases that did not fully chamber did have slightly thicker case walls but not always (That's how I found the inconsistency of case wall thickness on the same case). So it was out-of-round finished rounds that were causing the failure to fully chamber ... so I thought. When I adjusted the taper crimp die so measurement at case mouth was .378" (.380"+ will not chamber in the tight chamber Lone Wolf barre with no leade) with not out-of-round rounds, the rounds still did not fully chamber. That's when I realized failure to fully chamber was caused by bulging of CASE NECK below the case mouth, particularly near bullet base where taper crimp die won't reach.
So, it is not just the case wall thickness at case mouth we need to focus on but the case wall thickness near bullet base. I could use the Lee FCD to "fix" these rounds so they would fully chamber but that's not the focus of this thread.
Of course, measuring case wall thickness at bullet base seating depth is not easy as resized case length varies and finished OAL varies which in turn will vary the bullet seating depth ... so no measuring of case wall thickness at bullet base seating depth.
That's why I started this "Neck Tension and Bullet Setback" thread instead as measuring bullet setback is easier and factors in other variables.
I know. I know. I can already hear the keyboards clicking away to point out the variables of variables but I figured, this is one data set I can use for the "Mother Of All Bullets" thread. I can already see that I will end up using a particular headstamp cases with specified resized case length.
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agreed. that is why i posted my spreadsheet in post #12.
the 45acp case is not tapered so should not be affected here. but, i will still test the pmc cases and see if a large variance in case mouth thickness has any affect on accuracy.
these are great threads, bds. and i will contribute as much as i can.
thx,
murf
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