Myth Busting Neck Tension and Bullet Setback

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fxvr5 said:
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.

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.
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Good point. I have a feeling we'll end up with particular headstamp cases and lengths to produce smallest shot groups.
Walkalong said:
I thought this was just about bullet setback and safety concerning pressures. Maybe I read it wrong.
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This thread is prelude to upcoming "Mother Of All Bullets" thread to standardize and finalize my test loads for that thread (Any question raised will be linked back to this thread).

After this thread is concluded, next thread will be "Search For Most Consistent Metering and/or SD Producing Powders" using the headstamp cases and lengths this thread deems most suitable.

THEN we will start the "Mother Of All Bullets" thread using the brass and powder combo that proved most consistent. Yes, thanks to Bart B. and jmorris (Their comments have been my guiding lights), I have spent a lot of time thinking, ordering, testing, thinking again, testing more to have arrived at current thread.
 
bds said:
Good point. I have a feeling we'll end up with particular headstamp cases and lengths to produce smallest shot groups.

This thread is prelude to upcoming "Mother Of All Bullets" thread to standardize and finalize my test loads for that thread (Any question raised will be linked back to this thread).

After this thread is concluded, next thread will be "Search For Most Consistent Metering and/or SD Producing Powders" using the headstamp cases and lengths this thread deems most suitable.

THEN we will start the "Mother Of All Bullets" thread using the brass and powder combo that proved most consistent. Yes, thanks to Bart B. and jmorris (Their comments have been my guiding lights), I have spent a lot of time thinking, ordering, testing, thinking again, testing more to have arrived at current thread.
Click to expand...

With well over 100 bullets to choose from, how many bullets will you include in your study?

There is evidence that consistent velocity SD is NOT positively correlated to accuracy. https://americanhandgunner.com/exclusive-consistent-velocity-accuracy/ Also, that same article shows that the most consistent velocity SD powder, True Blue, produced larger groups than Power Pistol which had wide velocity spreads, though they were tested with different bullets.

If setback (differences or changes in OAL) is part of what you want to include in your results, are you going to measure the OAL of every round in the chamber, which suggests that you would have to hand-place every round in the chamber so that the OAL does not change from when it feeds from the magazine?

If you're just testing headstamps against one another, are you also going to measure their volume to make sure that doesn't contribute to changes in pressure/velocity which could be responsible for differences in accuracy?

A single 10-shot group isn't going to be compelling unless they differ by a factor of 4 or so. Why? Because in the American Handgunner article, that author found about a 2.8-fold difference in group size shooting the exact same load (with Power Pistol) from the same gun, and he was shooting 15-shot groups (and from a Ransom Rest) which is more rigorous than a 10-shot group. Thus, the normal variation in group size with the same load in the same gun can vary considerably.
 
fxvr5, please read the OP disclaimer.
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.
Click to expand...

I am simply going to make 3 dummy rounds for each headstamp per bullet type and measure the OAL/COL before and after they are fed/chambered from the magazine in Glock 22/KKM barrel and Glock 23/Lone Wolf barrel.

Please read post #49 which will answer many of your questions - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-2#post-10711561
bds said:
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.
Click to expand...
 
reddog81 said:
The data provides some interesting insights, however the sample is much too small to draw any conclusions.
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I agree, very valid points. And that's why I am increasing the sample size by repeating the measurements using random brass and different brands of bullets. If certain headstamps continue to experience bullet setback, they are less likely to maintain consistent "chambered" OAL/COL.

I will be measuring Hunting Shack Munitions bullets next and PowerBond/Rainier bullets afterwards.
 
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Continuing from Measurement #2 where X-Treme 100 gr plated RNFP was used - https://www.thehighroad.org/index.p...sion-and-bullet-setback.830072/#post-10710859

- Frankford Arsenal dial calipers verified with .355"+ pin gauge - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10523549
- Lee dies were used
- Finished OAL used was around 1.040"
- Since bullets were sized .355", taper crimp used was .377" - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10567453
- Dummy rounds (no powder, no primer) were measured before/after they were fed/chambered in Glock 22/23 using KKM/Lone Wolf 40-9 conversion barrels and 9mm magazines without riding the slide

Measurement #2 with X-Treme 100 gr plated RNFP at 1.040" OAL:

These headstamp cases did not experience bullet setback:
  • CBC
  • GECO
  • S+B
  • Starline
  • WIN
These headstamp cases experienced bullet setback (After Glock 22/KKM barrel, After Glock 23/Lone Wolf barrel):
  • AGUILA: -.0005", -.0005"
  • AGUILA: -.001", -.001"
  • AGUILA: -.0005", -.0005"
  • BLAZER: -.002", -.002"
  • BLAZER: -.001", -.002"
  • BLAZER: -.002", -.003"
  • FC: -.001", -.001"
  • FC: -.002", -.002"
  • FC: -.0005", -.0005"
  • .FC.: -.002", -.002"
  • .FC.: -.001", -.001"
  • .FC.: -.001", -.001"
  • GFL: -.001", -.001"
  • GFL: 0.0", 0.0"
  • GFL: 0.0", 0.0"
  • PERFECTA: -.001", -.001"
  • PERFECTA: -.0005", -.001"
  • PERFECTA: -.0005", -.0005"
  • PMC: -.001", -.001"
  • PMC: 0.0", 0.0"
  • PMC: 0.0", 0.0"
  • PPU: -.0005", -.001"
  • PPU: -.0005", -.0005"
  • PPU: 0.0", 0.0"
  • R-P: -.001", -.001"
  • R-P: -.001", -.001"
  • R-P: 0.0", 0.0"
  • SPEER: -.001", -.002"
  • SPEER: -.002", -.002"
  • SPEER: -.001", -.002"
  • Tulammo: -.0005", -.001"
  • Tulammo: -.0005", -.0005"
  • Tulammo: 0.0", 0.0"
NOTE: For subsequent measurements, removing Aguila/PPU/Speer/Starline/S+B brass as I do not have sufficient amount for random testing. Also removing FC brass as I have plenty of .FC. brass.


For Measurement #3, Hunting Shack Munitions 115 gr plated RN was used:

Measurement #3 with Hunting Shack Munitions 115 gr plated RN at 1.130" OAL:

These headstamp cases did not experience bullet setback:
  • GECO
  • R-P
  • WIN
These headstamp cases experienced bullet setback (After Glock 22/KKM barrel, After Glock 23/Lone Wolf barrel):
  • BLAZER: -.001", -.001"
  • BLAZER: -.0005", -.001"
  • BLAZER: -.001", -.0005"
  • CBC: 0.0", -.0005"
  • CBC: 0.0", 0.0"
  • CBC: 0.0", 0.0"
  • .FC.: -.001", -.001"
  • .FC.: -.001", -.001"
  • .FC.: -.001", -.001"
  • GFL: -.0005", -.0005"
  • GFL: 0.0", 0.0"
  • GFL: -.0005", -.0005"
  • PERFECTA: 0.0", 0.0"
  • PERFECTA: -.0005", -.0005"
  • PERFECTA: 0.0", 0.0"
  • PMC: -.0005", -.0005"
  • PMC: -.001", -.001"
  • PMC: -.0005", -.0005"
  • Tulammo: -.0005", 0.0"
  • Tulammo: 0.0", 0.0"
  • Tulammo: 0.0", 0.0"
 
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But if I am wrong and we are going to end up comparing all this to accuracy testing, it's going to be hard to prove one way or the other. :)
 
Blue68f100 said:
BE shooters like the brass length 0.002-0.003" from what the chamber is. Most shoot for a min length since most brass runs short.
Click to expand...
thx for that. i'm going to go with the min/max in the reloading manual for culling brass in my test, but it is good to know that precision handgun case prep is like precision rifle case prep, as little slop as possible on the head clearance.

murf
 
Just for clarifications sake... Is the Hunting Shack Munitions is loaded mixed headstamp ammo purchased from a retailer?
 
Case Wall Thickness - Since there was quite a bit of discussion on case wall thickness, I did some more measuring to shed light on "inconsistency" of case wall thickness and why we cannot just take one measurement per case. ;) Too much variance I saw with case wall thickness is reason why I did not pursue the "Myth Busting Case Wall Thickness" thread and instead started this "Myth Busting Neck Tension and Bullet Setback" thread.

Since some reloaders chamfer the inside of case mouth, instead of .050" depth, I took my measurements at .100" depth and four (4) times around the case neck at 12/3/6/9 O'clock.

NOTE: Cases were full-length resized, flared and full-length resized again to straighten the brass at case mouth to eliminate measuring of residual taper crimp/bent case mouth.

- Frankford Arsenal dial calipers verified with .355"+ pin gauge - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10523549
- Lee dies were used

Measurement #4 - Case Wall Thickness .100" below case mouth (Caliper jaw taped at .100"):

AGUILA: .0125"/.0125"/.0125"/.0125"
AGUILA: .011"/.0125"/.0125"/.011"
AGUILA: .013"/.012"/.011"/.010"

BLAZER: .010"/.011"/.010"/.011"
BLAZER: .0105"/.0105"/.0105"/.0105"
BLAZER: .010"/.0105"/.010"/.011"

CBC: .013"/.013"/.012"/.012"
CBC: .013"/.0125"/.0125"/.012"
CBC: .013"/.013"/.013"/.012"

.FC.: .011"/.011"/.011"/.011"
.FC.: .0105"/.0105"/.0105"/.011"
.FC.: .0105"/.011"/.0105"/.012"

GECO: .012"/.011"/.012"/.012"
GECO: .012"/.0125"/.0125"/.012"
GECO: .012"/.012"/.013"/.0125"

GFL: .010"/.011"/.013"/.012"
GFL: .012".0105"/.012"/.0105"
GFL: .011"/.013"/.013"/.011"

HRTRS: .012"/.013"/.012"/.013"
HRTRS: .013"/.012"/.012"/.013"
HRTRS: .012"/.013"/.013"/.012"

PERFECTA: .013"/.012"/.011"/.012"
PERFECTA: .012"/.013"/.012"/.011"
PERFECTA: .013"/.011"/.012"/.012"

PMC: .011"/.012"/.011"/.012"
PMC: .012"/.012"/.012"/.011"
PMC: .011/.012"/.011/.011"

PPU: .013"/.013"/.013"/.012"
PPU: .013"/.014"/.012"/.012"
PPU: .0125"/.0135"/.0135"/.0125"

R-P: .010"/.014"/.010"/.013"
R-P: .014"/.012"/.011"/.012"
R-P: .011"/.011"/.012"/.012"

S+B: .012"/.013"/.012"/.013"
S+B: .013"/.014"/.013"/.012"
S+B: .012"/.0135"/.0125"/.012

SPEER: .011"/.011"/.011"/.011"
SPEER: .010"/.011"/.011"/.010"
SPEER: .009"/.011"/.010/.011" (This case was measured 3 times with similar results on .009")

Starline: .011"/.011"/.012"/.011"
Starline: .013"/.011"/.010"/.011"
Starline: .010"/.011"/.011"/.011"

Tulammo: .013"/.012"/.011"/.011"
Tulammo: .014"/.012"/.011"/.012"
Tulammo: .014"/.013"/.014"/.012"

WIN: .011"/.011"/.011"/.012"
WIN: .012"/.011"/.012"/.010"
WIN: .010"/.012"/.011"/.011"
 
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Thinner case wall brass producing less neck tension and greater bullet setback is understandable, but here is the question we should all be asking:

Since Measurement #2 and #3 demonstrated bullet setback by thicker case wall brass, what factors caused the decrease in neck tension?

BTW, all the brass came from same indoor ranges and processed/cleaned/polished the same (Inside of most cases were clean) with walnut/corn cob media by ljnowell - https://www.thehighroad.org/index.php?threads/brass-for-sale-9mm-380-45-40-il.820011/#post-10550945
 
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Yes, plenty - https://www.thehighroad.org/index.p...n-9mm-40s-w-45acp.799231/page-4#post-10338994

I have been testing Berry's, HSM, Hornady HAP, PowerBond, Rainier, Remington, RMR, Speer TMJ, Winchester, X-Treme, Zero regular and thick plated bullets along with jacketed bullets in preparation for the "Mother Of All Bullets" thread in the works.

As to plated bullets coming apart, I believe that myth has been busted many times over with too much crimp cutting through the copper plating as primary culprit and plated bullets pushed past their rated fps as second - https://www.thehighroad.org/index.p...ng-at-25-50-yards.808446/page-3#post-10470195

I pushed RMR 100 gr Hardcore Match Plated RN (Thick plated rated to 1500 fps) to almost 1500 fps with 2" 50 yard 10 shot groups so I figure the plating stayed intact - https://www.thehighroad.org/index.p...n-9mm-40s-w-45acp.799231/page-3#post-10245856

RMR HM 100 gr RN (.356") at 1.050" OAL with .378" taper crimp:
5.5 gr HP-38: 1493-1468-1432-1479-1454 fps
4.5-4.7 gr Promo: 1478-1475-1480-1471-1467 fps

index.php
 
bds said:
Thinner case wall brass producing less neck tension and greater bullet setback is understandable, but here is the question we should all be asking:

Since Measurement #2 and #3 demonstrated bullet setback by thicker case wall brass, what factors caused the decrease in neck tension?

BTW, all the brass came from same indoor ranges and processed/cleaned/polished the same (Inside of most cases were clean) with walnut/corn cob media by ljnowell - https://www.thehighroad.org/index.php?threads/brass-for-sale-9mm-380-45-40-il.820011/#post-10550945
Click to expand...
My observation is that you need to measure the case wall thickness further down the case. The case walls on 9mm taper in thickness, they get thicker further down. Most of the cases I checked also don't start the taper until you get below about 0.20" below the mouth, in other words they are constant wall thickness for some distance, before they start to taper. It is my opinion that it is not the neck tension at the case mouth that hold the bullet, it is the neck tension further down where the wall gets thicker. In addition, the notorious "coke bottle" shape that we sometimes get in 9mm, especially with 147gn bullets, forms a sort of shoulder that the heel of the bullet sets on.

Like I said earlier, there are some headstamps that start the taper right at the case mouth, and IMHO these would be best for 115gn bullets. The ones that don't start the taper further down would be better for the heavier bullets.
 
I think the non-correlation between case thickness and neck tension is a very interesting observation. It certainly appears that the "springiness" and/or hardness of the brass is perhaps a more significant factor in predicting tension than thickness.

I kind of reached that conclusion on my own when trying to sort out setback issues in 10mm PPU brass (which had been reloaded more than once or twice). Despite lots of measuring, I just couldn't come up with any measurement that would predict which cases would lose tension or not. I tentatively concluded it was simply that the brass PPU used for those cases was prone to work hardening or some similar phenomenon and that some of the cases simply wouldn't re-size down far enough to grab the bullets. Annealing is not in my bag of reloading tricks, although I did make a clumsy, amateurish attempt at it with a few of those cases that showed a loss of tension, and found no improvement.
 
Toprudder said:
you need to measure the case wall thickness further down the case
Click to expand...
Good point as more neck tension is applied to the bullet base by thicker case neck towards bullet base - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-2#post-10711411
bds said:
  • 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.
Click to expand...
 
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For Measurement #5, caliper jaw was taped at .200" and that was around the bullet seating depth for HSM 115 gr RN loaded to 1.130".

NOTE: Cases were full-length resized, flared and full-length resized again to straighten the brass at case mouth to eliminate measuring of residual taper crimp/bent case mouth.

- Frankford Arsenal dial calipers verified with .355"+ pin gauge - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10523549
- Lee dies were used

Measurement #5 - Case Wall Thickness .200" below case mouth (Around bullet seating depth for HSM 115 RN at 1.130" OAL):

AGUILA: .013"/.013"/.014"/.014"
AGUILA: .012"/.013"/.013"/.013"
AGUILA: .012"/.013"/.014"/.013"

BLAZER: .011"/.012"/.011"/.010"
BLAZER: .010"/.010"/.012"/.011"
BLAZER: .012"/.011"/.011"/.012"

CBC: .015"/.014".014"/.015"
CBC: .015"/.015"/.014"/.015"
CBC: .014"/.015"/.014"/.013"

.FC.: .013"/.012"/.012"/.011"
.FC.: .011"/.011"/.012"/.010"
.FC.: .011"/.012"/.012"/.011"

GECO: .014"/.014"/.0125"/.014"
GECO: .014"/.014"/.014"/.015"
GECO: .014"/.013"/.014"/.013"

GFL: .012"/.012"/.013"/.013"
GFL: .014"/.014"/.013"/.012"
GFL: .015"/.013"/.0125"/.014"

HRTRS: .0125"/.0135"/.0135"/.0125"
HRTRS: .014"/.014"/.012"/.013"
HRTRS: .013"/.014"/.013"/.012"

PERFECTA: .014"/.013"/.012"/.012"
PERFECTA: .014"/.014"/.012"/.013"
PERFECTA: .015"/.014"/.013"/.012"

PMC: .011"/.013"/.012"/.012"
PMC: .012"/.012"/.012"/.012"
PMC: .0125"/.0125"/.013"/.0125"

PPU: .014"/.014"/.014"/.013"
PPU: .015"/.015"/.013"/.014"
PPU: .013"/.014"/.014"/.013"

R-P: .013"/.011"/.012"/.014"
R-P: .012"/.012"/.014"/.012"
R-P: .012"/.012"/.013"/.012"

S+B: .013"/.014"/.0125"/.013"
S+B: .015"/.014"/.014"/.013"
S+B: .013"/.013"/.013"/.0125"

SPEER: .010"/.011"/.011"/.011" (.010" measurement tripled checked with similar results)
SPEER: .010"/.011"/.012"/.011" (.010" measurement tripled checked with similar results)
SPEER: .012"/.011"/.012"/.012"

Starline: .012"/.012"/.013"/.012"
Starline: .012"/.013".012"/.011"
Starline: .012"/.012"/.013"/.013"

Tulammo: .015"/.013"/.014"/.012"
Tulammo: .014"/.015"/.014"/.014"
Tulammo: .015"/.013"/.011"/.012"

WIN: .014"/.013"/.0125"/.013"
WIN: .013"/.013"/.0125"/.012"
WIN: .015"/.014"/.013"/.014"
 
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So far, we have following data to work with:
 
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Don't you mean 0.200" below the case mouth instead of 0.020"?
 
Funny that I just logged back on and saw your last post, BDS. I just finished loading 100 rounds of Zero 125JHP bullets, and I had several fail the case gage check (but they chambered fine in my gun). The problem was the case bulge at the bottom of the bullets, and the offending cases were several CBC and one Tulammo. I have to seat the Zero bullets to 1.080" for my gun, which puts the base of the bullet a little further down in the case.
 
I have similar problem with my Lone Wolf barrel that has tight chamber and no leade. Thicker walled cases won't fully chamber and CBC being the worst case as it showed .0144" average case wall thickness at .200" below case mouth (see bottom of next post).

Also, check the sizing of the bullet. Zero 9mm 115 gr FMJ I have are .356" in diameter - https://www.thehighroad.org/index.p...re-sized-the-same.818806/page-2#post-10567453

So thicker case wall is not always better if you are using tighter chamber/shorter leade barrels, especially with larger sized bullets.
 
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I calculated the average bullet setback sorted by no bullet setback to most bullet setback and case wall thickness from thickest case wall to thinnest case wall.

It's interesting to note that AGUILA/CBC/GFL/PERFECTA/PPU/Tulammo cases measured thicker .200" below case mouth than Starline yet experienced bullet setback in Measurement #2 and #3 while Starline/WIN cases did not experience bullet setback. There likely is other factor at play for thinner Starline and Winchester brass to not experience bullet setback, such as brass quality.


Average Bullet Setback from Measurement #2 with X-Treme 100 gr plated RNFP at 1.040" OAL:

.0000" - CBC
.0000" - GECO
.0000" - S+B
.0000" - Starline
.0000" - WIN
.0003" - GFL
.0003" - PMC
.0004" - PPU
.0004" - R-P
.0004" - Tulammo
.0006" - AGUILA
.0007" - PERFECTA
.0012" - FC
.0013" - .FC.
.0016" - SPEER
.0020" - BLAZER


Average Bullet Setback from Measurement #3 with Hunting Shack Munitions 115 gr plated RN at 1.130" OAL:

.0000" - GECO
.0000" - R-P
.0000" - WIN
.00008" - CBC
.00008" - Tulammo
.0001" - PERFECTA
.0003" - GFL
.0006" - PMC
.0008" - BLAZER
.0010" - .FC.


Average Case Wall Thickness .100" Below Case Mouth (Thickest to thinnest):

.0129" - PPU
.0126" - S+B
.01256" - CBC
.0125" - HRTRS
.0124" - Tulammo
.0121" - GECO
.0120" - PERFECTA
.0119" - AGUILA
.0116" - R-P
.01158" - GFL
.0115" - PMC
.0111" - WIN
.0110" - Starline
.0108" - .FC.
.0105" - SPEER
.0104" - BLAZER


Average Case Wall Thickness .200" Below Case Mouth (Around Bullet Seating Depth for HSM 115 gr RN at 1.130" OAL):

.0144" - CBC
.0138" - PPU
.0137" - GECO
.0135" - HRTRS
.0135" - Tulammo
.0133" - S+B
.0132" - WIN
.0131" - GFL
.0130" - AGUILA
.0130" - PERFECTA
.01225" Starline
.0122" - PMC
.0121" - R-P
.0115" - .FC.
.0111" - SPEER
.0110" - BLAZER
 
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