Researchers slant data all the time.Rule3 said: "The researcher can pretty much make the results come out how ever they want by the sample size."
That's not true. It's a layman's myth. Researchers are bound by what their data says.
Researchers slant data all the time.Rule3 said: "The researcher can pretty much make the results come out how ever they want by the sample size."
That's not true. It's a layman's myth. Researchers are bound by what their data says.
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.
Researchers slant data all the time.
Show your evidence.
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.
DISCLAIMER: Testing conducted for this thread was done by a random poster on the internet forum with possible unreliable equipment. Test data deemed unscientific and use them at your own risk.
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-10523549What measuring instrument was used to measure .001 variance?
- Frankford Arsenal dial calipers verified with .355"+ Class ZZ pin gage
Now, let's get back to the OP goal of myth confirming or busting "Neck Tension and Bullet Setback".
No, range testing will be conducted as mentioned in post #9 - https://www.thehighroad.org/index.p...sion-and-bullet-setback.830072/#post-10710859Does this mean no accuracy testing?Now, let's get back to the OP goal of myth confirming or busting "Neck Tension and Bullet Setback".
If you are going to test accuracy, can you please explain your methods? Thanks.
As to the range testing methods, same as how I have done other load developments and powder work ups on THR:I will next do a comparison range test
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).Now, let's get back to the OP goal of myth confirming or busting "Neck Tension and Bullet Setback".
..
As to the range testing methods, same as how I have done other load developments and powder work ups on THR:
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").
- 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
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.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).
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.
murf
p.s. this falls under the "neck tension" catagory!
thanks for the tip. any particular length you can recommend?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.I thought this was just about bullet setback and safety concerning pressures. Maybe I read it wrong.
thanks for the tip. any particular length you can recommend?
murf
agreed. that is why i posted my spreadsheet in post #12.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 this LW barrel) 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, especially 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 but the case wall thickness near bullet base.