Does concentricity matter ?

[GeoDudeFlorida]

If a bullet is seated crooked——neck tension has been effected.
If the chamber corrects said crooked bullet—neck tension has further been effected.
If the leade corrects the crooked bullet by jam—-neck tension has been deemed almost irrelevant.
Therefore if concentricity has no effect on the round, but effects neck tension, and neck tension is a “massive influence” on primary ignition—- doesn’t that state the concentricity has an influence on the round…??

However, unless you are placing many in the same hole from a distant galaxy, this almost seems to be a mute point…

……oh yeah….IMO…..



……..and, blah, blah, blah…..

Exactly! Which is why I pointed out early on: making straight cases is more important than checking for straight bullets post-seating; and, if you are single-loading a tight chamber to or almost to the leade then neck tension approaches irrelevance.
Plan to be ignored by the “elite class” arguing among themselves, though. We’re not supposed to know these things. )

 

[Varminterror]

Plan to be ignored by the “elite class” arguing among themselves, though. We’re not supposed to know these things. )

Your original comment - make straight cases, don't worry about measuring - was agreed by many of us posting here...

What's the purpose of your self-pity party now on page 5?

 

[CQB45ACP]

They'd be able to tell you who likes 2 buck chuck or Chateau Mouton!

The conversations would probably be along the same lines. Who's right/wrong, what's the best answer...

Years ago (late 70s maybe very early 80s) I bought a bottle Château Lafitte R. to taste what the hoopla was all about. Don't remember price but probably $100.

Went to open it and the cork pushed completely into the bottle. The wine was awful of course--vinegar or worse. Took it back and got a refund and never tried a Premier Grand Cru after that. Lesser cru, yes, but eventually got over myself and saved my money to eventually spend it and more on reloading.

Even if I don't understand everything being discussed here, it's still worthwhile to learn what I can.

 

[Varminterror]

Sigh...

If a bullet is seated crooked——neck tension has been effected.

This isn't inherently true of itself - it's non-sequitur. Neck tension is defined as the difference in the sum of 2x the thickness of the brass + the diameter of the bullet vs. the OD of the finished round. Being crooked does not inherently change the dimensions expressed here.

However, ALL of the tests presented in this thread by independent shooters have supported that any presumed influence has been repeatedly proven to NOT influence group size.

If the chamber corrects said crooked bullet—neck tension has further been effected.

Equally, this is non-sequitur. We have no information that shows (2x brass thickness) + (bullet dia) - (dia of finished round) has changed before or after a cartridge has been straightened.

However, ALL of the tests presented in this thread by independent shooters have supported that any presumed influence has been repeatedly proven to NOT influence group size.

If the leade corrects the crooked bullet by jam—-neck tension has been deemed almost irrelevant.

This statement is wholly non-sequitur. Patently false claim with no scientific merit.

Therefore if concentricity has no effect on the round, but effects neck tension, and neck tension is a “massive influence” on primary ignition—- doesn’t that state the concentricity has an influence on the round…??

False assumptions yield false conclusions. Pretty simple. Neck tension influences primary ignition, and your premise that concentricity significantly influences neck tension is non-sequitur.

However, unless you are placing many in the same hole from a distant galaxy, this almost seems to be a mute point…

*moot

Yes, it has been stated by many folks many times in this thread, concentricity measurement of produced ammunition and any resulting culling or sorting of ammunition thereafter is either meaningless to all shooters or meaningless to all but a near-zero number of shooters.

 

[Mk-211]

Even if I don't understand everything being discussed here, it's still worthwhile to learn what I can.

Agree 100%

I'm not a wine connoisseur either, $2 Chuck wasn't a bad wine. My wife likes riesling wines, so we usually get them.

 

[JFrank]

Let’s all remember that this is just a discussion. I’ll always promote testing for one’s own combination.

 

[Soonerpesek]

SIGH…!!

Neck tension is defined as the difference in the sum of 2x the thickness of the brass + the diameter of the bullet vs. the OD of the finished round

Using your words:
If you seat a bullet, and then crook same bullet, the difference in the sum of 2x the thickness of the brass + the diameter that the crooked bullet just created is indeed different.

False assumptions yield false conclusions. Pretty simple. Neck tension influences primary ignition, and your premise that concentricity significantly influences neck tension is non-sequitur.

Nothing I stated is false…

moot

…and no…..mute, as in silent.
Not moot as in forgotten…
Thanks for attempting to be my grammar instructor tho….



We can, and have, gone round and round with this. Each of us with the belief we are correct.
Some of us don’t have big bro mods to side with us even though our statements are construed as legitimate…

 

[Nature Boy]

I don't mess with neck tension (or if you prefer JFrank/FGuffey, "Bullet Hold" ) for the same reason I don't worry about run out. I had custom dies made to the same dimensions as my rifle's chamber. This eliminates concentricity issues (<0.002 TIR) and keeps my neck tension a constant 0.002.

Now I know some folk subscribe to the method of using neck bushings in the sizing die to adjust neck tension as another tuning knob to twist. That would be a good discussion for another thread.

Time being a finite resource, I put as much effort into finding reasons NOT to do certain steps as I do in pursuit of optimizing my loads for the most accuracy.

 

[Varminterror]

If you seat a bullet, and then crook same bullet, the difference in the sum of 2x the thickness of the brass + the diameter that the crooked bullet just created is indeed different.

This is an inherent fallacy. There's no scientific founding to say that turning the bullet and neck has done anything to the diameter of the bullet nor the thickness of the neck.

Quite the opposite, we can observe when we DO use the Hornady concentricity tool to bend ammo, we do NOT see a shift in the diameter...

So what you're saying is that if I'm laying down, my belt size gets larger than when I'm standing... which, of course, is false, so making the claim is a non-sequitur argument.

 

[Varminterror]

Time being a finite resource, I put as much effort into finding reasons NOT to do certain steps as I do in pursuit of optimizing my loads for the most accuracy.

BINGO, amigo!

I'd rather spend time helping new reloaders realize they don't need to weight sort brass or trim meplats or uniform primer pockets or turn necks or measure concentricity by sharing all of these other tests generously performed by other shooters to show none of these matter than spend any of my time turning a knob which doesn't do anything, or watching new shooters get mislead to thinking they need to turn these knobs!

One of my mentors in Lean Manufacturing used to use the phrase "Fix the part (of the process) where the part (product) gets broken." Doing anything else is just creating waste.

 

[Soonerpesek]

View attachment 1192241



This is an inherent fallacy. There's no scientific founding to say that turning the bullet and neck has done anything to the diameter of the bullet nor the thickness of the neck.

Quite the opposite, we can observe when we DO use the Hornady concentricity tool to bend ammo, we do NOT see a shift in the diameter...

So what you're saying is that if I'm laying down, my belt size gets larger than when I'm standing... which, of course, is false, so making the claim is a non-sequitur argument.

Obviously not saying the diameter of the BULLET has changed….that I did not imply…
The diameter of the space between the walls has increased when the bullet was crooked…
Concurrently will effect neck tension that you have stated has a massive influence.

Explain to me where that statement is incorrect….

 

[Varminterror]

The diameter of the space between the walls has increased when the bullet was crooked…

Proof of the claim is the burden of the claimant.

Bend some bullets, measure that space, present the data here, prove your claim.

Otherwise, you're imagining something which you have made no attempt to actually prove is happening, but rather, thousands and thousands of us have proof is NOT happening...

 

[JFrank]

I don't mess with neck tension (or if you prefer JFrank/FGuffey, "Bullet Hold" ) for the same reason I don't worry about run out. I had custom dies made to the same dimensions as my rifle's chamber. This eliminates concentricity issues (<0.002 TIR) and keeps my neck tension a constant 0.002.

Now I know some folk subscribe to the method of using neck bushings in the sizing die to adjust neck tension as another tuning knob to twist. That would be a good discussion for another thread.

Time being a finite resource, I put as much effort into finding reasons NOT to do certain steps as I do in pursuit of optimizing my loads for the most accuracy.

Good one bro’
I test lots of dumb stuff, if it makes a difference on the target I’m interested, if not I move on.

Neck tension is still measured in pounds not tensions . F.Guffey..

 

[zeke]

So then a chamber would need to fix the eccentric ammo in order for runout not to matter. The evidence suggests that a very accurate rifle that likely has a chamber machined by a custom reamer corrects the eccentricity such that it is still very accurate when badly eccentric cartridges are fed.

Now suppose I have a factory Ruger rifle rather than a BAT custom. Does runout of the cartridges that I feed start to matter? My chamber might not be so tight that it fixes eccentric ammo, so does that mean I need to pay more attention to runout so the cartridge is concentric even in a relatively loose chamber? If so, to what degree can I benefit from controlling runout and by how much?

This is way too generalized for any complete answer to your questions. However, does the rifle and ammo being used meet your needs/purpose for the rifle? Do you reload?
And while very basic , and cheap, you can roll your rounds on a flat hard surface at eye level to see if you can observe the bullet "wobbling". Yes it is very low tech, but imo serious runout is easily observed. Then go from there. Am not in possession of a rifle that can fix each rounds runout to .0025, nor do i jam bullets into the rifling. So for my purposes runout certainly does matter. Especially if there are very basic (and free/cheap) ways to minimise it.

 

[Varminterror]

So let's circle the wagons a little bit...

Let's design an experiment:

Hypothesis: Ammunition concentricity influences precision (Or the related hypothesis - DOES Ammunition concentricity influence precision)

Results presented in this thread and arguments there against, and corresponding influence on future proposed tests:

* EXTREMELY bent ammunition was shown to have deminimis influence on 1000yrd groups when bullets are jammed into the lands - the counterpoint was that this was 1000yrd shooting which is believed to have greater sensitivity to other error influences than would 100yrd/200yrd groups. An additional counterpoint was presented that this test did not show how much the rifle chamber was straightening the ammunition prior to firing. Further testing should therefore be conducted at short range where mechanical precision is not overwhelmed by bullet flight and further testing must include chambering then removing the ammunition to remeasure to determine how much influence the rifle chamber has on straightening the ammunition prior to firing.

* EXTREMELY bent ammunition was shown to have been straightened by a rifle chamber and the groups again at 1000yrds were not influenced in any meaningful way even when bullets are jumped - the counterpoint was that this was a custom action with a tight freebore, and a subsequent hypothesis was presented that a more generous freebore would not straighten ammunition in the same way. Further testing must be done either to determine how much a "standard" chamber would straighten ammunition and/or to determine how much more or less a "standard chamber" straightens ammunition vs. a custom chamber.

* A Factory PISTOL was used to show that bullets seated from EXTREMELY crooked position did not produce larger groups. A counterpoint I would make (not previously presented in the thread) would be that the article did not show actual eccentricity measurements.

So the experimental design here MUST include:

1. Short range group shooting
2. Factory rifle with presumed "loose" chambers (or a combination of factory and custom chambers)
3. Details about chamber dimensions for respective rifle chambers
4. Measurement of eccentricity prior to chambering and residual eccentricity after chambering (remove ejector to prevent bending of ammo by ejection process, hand feed ammunition into chamber to prevent bending of ammo by feeding process
5. Statistically sufficient roundcounts of each control and experimental sets to establish valid conclusions based on known differentiation tests (such as T-tests)
6. Control group of non-sorted/non-fixed/non-culled ammunition
7. Control group of culled ammunition with minimum/near-zero runout
8. Experimental groups of bent ammunition with varying eccentricity
9. Measurement of neck OD prior to chambering and thereafter (including measurement prior to bending if a manual method of bending is used) to determine influence on neck tension by the bending and straightening steps of chambering the ammo

+ One problem I can observe is the refusal to accept results - as has been stated in this thread, any results by any shooter not on a short list of world class competitors would undermine validity (for some reason?) of any test results... Access to world class short range benchrest shooters is relatively limited, so like most folks on this forum, I'd have a bit of trouble sourcing one.

Questions for input to design:

• If a manual method of bending ammunition is used, is brand/model of dies pertinent to the experiment? The control and experimental sets will be manually sorted or mechanically modified, so the eccentricity or concentricity promoted by any specific die would be null.
• Is there any argument towards a controlled method of bending ammunition? The Hornady concentricity gauge and straightening tool can bend ammunition to relatively controlled runout
• What would be acceptable extent of runout to satisfy validity of the conclusions? I might propose a preparatory "experiment" of measurement of existing ammunition to determine common average and standard deviations

Any input to improvements for this experiment?

All of these experimental parameters thus far seem easily attainable by dozens of us, hundreds of us, present on this forum, so it sure seems like we could create a significant body of science here.

 

[Varminterror]

Am not in possession of a rifle that can fix each rounds runout to .0025

Could you share the data and details from this experiment?

Can you share the data and details of the experiment which shows runout greater than 0.0025 are broken and need be fixed?

 

[zeke]

Could you share the data and details from this experiment?

Can you share the data and details of the experiment which shows runout greater than 0.0025 are broken and need be fixed?

there's one in every crowd

 

[Varminterror]

@zeke - it seems like a fair question, and you've brought up the difference between the tests you've seen in this thread multiple times suggesting that factory chambers wouldn't do what do custom chambers. Persisting to say this even after you have been presented a test using a factory PISTOL which still showed that eccentricity didn't influence group sizes on the page...

So as mentioned above - the burden of proof to support the claim is on the claimant. Are you sure your rifles can't correct eccentricity? Are you sure that eccentricity above the 0.0025 you proposed is actually detrimental for your rifles? It seems fair to ask if you can prove what you've stated.

 

[Soonerpesek]

Proof of the claim is the burden of the claimant.

Bend some bullets, measure that space, present the data here, prove your claim.

Otherwise, you're imagining something which you have made no attempt to actually prove is happening, but rather, thousands and thousands of us have proof is NOT happening...

So…….I have to proof my claims, but you don’t…???!!!
I shouldn’t have to proof what is common sense….


Put a bar in a thin walled hole…
Pull the bar to you….
Observe that the space where the bar is has got maligned to be larger……
Do you really need pictures…..!!!???

 

[Laphroaig]

Jeff Siewart/Ammunition Demystified acknowledges in-bore yaw and discusses it on pgs. 404-406, among other places in the book. Pictorial evidence is shown on 405.

His take is that it's a significant factor in group size and can be minimized by tuning bullet jump. The way that I interpret what he is saying is that bullet concentricity isn't the only cause, which can also include the precision of your chamber and the construction of the bullet.

 

[Varminterror]

I have to proof my claims, but you don’t

You don't have proof.

Where have you proven that the neck is opening around the bullet? I've seen no data from you here. Just your assumptions.

 

[JFrank]

I could probably use a little common sense and suggest that if I moved the bullet back and forth a few times the case would loosen up a bit and since the brass won’t resize itself or have enough spring back the case neck would remain opened up that wee bit.
I might be wrong .. I just haven’t taken note

 

[Soonerpesek]

FINALLY…
This young man understands…!!^^^^^

 

[Soonerpesek]

You don't have proof.

Common sense needs no proof…..

 

[Varminterror]

I want to be clear here, I don't intend to seem like I'm arguing in this thread, but I think it's pretty fair to acknowledge the difference between assumptions and facts.

This is a topic I have studied for more than 20yrs, and I've NEVER seen anyone proving that concentricity is critical to precision, but I HAVE seen hundreds of people in dozens of threads like this claiming that "common sense" proves it... But I think it's pretty fair to ask folks to support their hypothesis - their common sense assumptions - to PROVE their claims, OR just acknowledge that assumptions based on common sense aren't always correct...

I WOULD ABSOLUTELY LOVE TO LEARN SOMETHING IF ANYONE ON THIS FORUM OR ANY OTHER COULD PRODUCE DATA WHICH REFLECTED DEFINITIVE ANSWERS TO THE HYPOTHESES BELOW.

I could probably use a little common sense and suggest that if I moved the bullet back and forth a few times the case would loosen up a bit and since the brass won’t resize itself or have enough spring back the case neck would remain opened up that wee bit.
I might be wrong .. I just haven’t taken note

This is making compounding assumptions that the bullets are bending far enough in the context of this discussion that the case won't spring back, and the assumption that the bullet and case neck are not moving together, but rather that the bullet is only moving part of the neck when being bent (in other words, assuming that the bullet is strong enough to "waller" the neck around to loosen it, but NOT strong enough to bend the entire neck)... Assumptions without data remain to be assumptions.

If you're willing to measure your runout, as you bend the cases and then measure your neck diameters, then you'd have proof to support the assumptions. But folks are promoting a lot of assumptions as if they were based in data and fact, rather than simple speculation. Common sense is great, but as we've seen in this thread, common sense would say that concentricity is critical to precision... But we have several experiments shown in this thread which show concentricity is NOT critical to precision...

Anyone with a 21st century Hydropress, K&M Force Pack Press, or AMP Press can test the change in break-free force after bending bullets and case necks. Anyone with a micrometer can measure OD of case necks after bending bullets and case necks. Just as the folks in these videos and articles conducted the experiments to test their hypothesis that concentricity influences accuracy and ended up with data which defied common sense, it would be exceptionally simple to conduct the measurements to prove or disprove the hypothesis that straightening bent ammunition reduces neck tension, and just as easy to prove the subsequent hypothesis that that change in neck tension would influence precision of the ammo...

Otherwise, we're all just assuming it's important and we're falling into the trap of the observational bias of assuming our assumptions are correct, and then stating them as facts...

I don't KNOW whether bullets seated with common equipment will have such eccentricity that when they bend straighter against chambers and leades that it would loosen their neck tension, because I have never seen data which showed case necks were stretched looser by the act of them being chambered and straightened. But I do know that as I've measured hundreds and hundreds of rounds for concentricity in the past, I didn't get a measurable change in the neck diameters based on the position of my dial indicators on the necks. I also know I didn't see any difference in precision when I used the hornady tool to straighten ammo vs. shooting raw "crooked ammo," and I didn't see any difference in precision when I shot groups of culled ammo vs. raw "crooked ammo." I also KNOW what we have seen in the videos and articles linked in these threads, and those presented in dozens of other threads like this... So I'm NOT prone to assume that 1) concentricity significantly influences precision, and 2) that the straightening of the ammo by the rifle negatively influences neck tension or resulting precision.

I WOULD ABSOLUTELY LOVE TO LEARN SOMETHING IF ANYONE ON THIS FORUM OR ANY OTHER COULD PRODUCE DATA WHICH REFLECTED DEFINITIVE ANSWERS TO THE ABOVE HYPOTHESES.

These are simple tests to do. A lot of folks can do them.

"Trust in God. All others, bring data."