Does concentricity matter ?

[Varminterror]

I solved any concentricity issues at the press, which negated the need to check for it or worry about it.

Yep, use equipment that minimizes run out, then check to make sure it’s still good

This really outlines the difference between QC and QA which most folks really don't grasp. Using equipment and processes makes good ammo is Quality Control, which are Lead Measures we implement to do the things which make good ammo. Measuring ammo AFTER it has been made is Quality Assurance, a Lag Measures which determines the result of the process, but does not actually improve the process or product being made. As a production philosophy then, if we concentricity sort our ammo, we are wasting time making ammo which won't do what we need. Alternatively, using a concentricity tool to determine which dies or brass to use to make quality ammo makes sense, as we're setting up a Quality Control process of Lead Measures which make good ammo. Using a concentricity tool to sort and cull ammo might produce the same ultimate product quality, but it's less efficient because it has wasted time and resources to achieve the same standard.

And of course, if you're not competing where the difference between shooting in the 0's and 1's matters, then the science out there which has been shared in this thread proves that concentricity doesn't influence precision enough to matter for you.

 

[Varminterror]

First, I don't think we watched the same video.

.006 ain't much for runout

Secondly, 6 thou is a lot of run out. Not unheard of, but for common dies and quality bullets and brass, 6 thou is a high outlier, not a typical average, and it certainly isn't apt to say "6 thou ain't much".

 

[westernrover]

I wanted a concentricity gauge a couple years ago, but was talked out of it on the forums. I also saw a video of Erik Cortina dismissing concerns about concentricity, saying he doesn't check for it because it doesn't matter -- to be specific, the concentricity of the loaded cartridge does not have a meaningful effect on the results on target. Whether that is because the chamber straightens it or it just doesn't effect the result once the bullet is in the bore, I don't know. I also don't know, if my chamber is just a relatively loose factory chamber and not made with a custom reamer like those guys that shoot competitively, does it matter then?

I think I'd have to answer the question, matter for what? What matters to me is being able to hit a small target with the first shot at distance -- say a coke can size target at 500 yards. That's "sub-MOA." I don't care about groups per-se, but I think groups are a practical way to measure a rifle and a load. I recognize the delta between grouping performance and what I actually want, but groups are still a practical thing to check function. I look at cold-bore accuracy, but how would I measure the effect of concentricity on cold-bore accuracy? The consistency I get with groups should translate to consistency in cold-bore shots, more or less.

 

[Varminterror]

I look at cold-bore accuracy, but how would I measure the effect of concentricity on cold-bore accuracy? The consistency I get with groups should translate to consistency in cold-bore shots, more or less.

This is a can of worms in itself.

"Clean bore" offset is real. "Cold bore" offset really isn't. If you're moving a goalpost to chase concentricity influence on cold bore accuracy, you're kinda trying to chase unicorns on a flying carpet. The testing would be exactly the same to prove concentricity influence on groups (precision) vs. cold-bore accuracy (confidence in precision such that a correct and accurate zero can be established), it would simply take longer to do the test as the shooter has to wait longer between shots. Not magic, not even difficult, but all signs point to a null hypothesis - unless you own a flying carpet and a field of unicorns.

 

[JFrank]

Things that I’m pretty sure have more influence on performance than concentricity. I could be wrong though.

Good barrels
Good bullets
Accurate powder weight
Seating depth
Correct bullet hold per application
Primers fully seated
Correct amount of firing pin fall
Strong firing pin spring
Good case prep
No stress on the action
Tune

Etc…

 

[Nature Boy]

it makes me all warm and fuzzy to not have “sloppy” ammo, so I’ll continue to make sure my match ammo straight enough to please me.

Pride in your product has its own merits

 

[PapaG]

Yes. For precision. Read FWMann’s The Bullets Flight” to learn what was known over a century ago.

 

[splattergun]

Am old fashioned, and my concentricity "gage" is rolling a finished round on a flat, hard and level surface. If i see the bullet wobbling at all, am wanting to know why and how to fix it.

I use this process on a mirror, which really makes any wobble really show up. I only do this on a batch basis though, to check my press more than anything else.

 

[CQB45ACP]

I watched the video and have read your comments and confess I understand little of it. I also did a quick search and see maybe a dozen concentricity gauges on the market. My guess is they'll keep selling em like always.

 

[Walkalong]

Yes. For precision. Read FWMann’s The Bullets Flight” to learn what was known over a century ago.

When the bullet comes out of the barrel it isn’t completely stabilized yet, but “settles in” shortly thereafter. If concentricity doesn’t matter at all, there’s where it’s happening. The spin settles it down.

Old timers liked longer .22 LR barrels not for speed, they lose speed, but to spin the bullet a touch more, theoretically making it more accurate, perhaps settling it down sooner…….dunno.

 

[berettaprofessor]

Secondly, 6 thou is a lot of run out. Not unheard of, but for common dies and quality bullets and brass, 6 thou is a high outlier, not a typical average, and it certainly isn't apt to say "6 thou ain't much".

Oh heck yes....I use Lee dies almost exclusively and rarely see anything over 0.002!

 

[zeke]

I use this process on a mirror, which really makes any wobble really show up. I only do this on a batch basis though, to check my press more than anything else.

At this point am only doing it occasionally, maybe every batch. There is no way i check every round. Can admit that i do not know how many thousandths of runout is easily observable.

 

[zeke]

First, I don't think we watched the same video.



Secondly, 6 thou is a lot of run out. Not unheard of, but for common dies and quality bullets and brass, 6 thou is a high outlier, not a typical average, and it certainly isn't apt to say "6 thou ain't much".

If runout doesn't matter enough to check, .006 is only .003 more than the control group? And considerably less than the runout that was tested in the first video. And if runout doesn't matter, why do the statistics ? The only way runout doesn't matter, is if your reloading procedure minimises it to a point it doesn't matter in the firearm and purpose the round is being used for. So can i ask if you measure or know the runout of the rounds you load?

 

[Varminterror]

if your reloading procedure minimises it to a point it doesn't matter in the firearm and purpose the round is being used for.

Yes, as directly stated above - the quality control of producing ammo which doesn't need to be sorted (or fixed) to produce sufficient precision for the task is the game. Then you don't need to worry about measuring produced ammunition as a matter of practice (quality assurance).

The problem, however, stems from the fact so many folks insist concentricity matters for their firearm when it's a factory rifle and their purpose is punching (relatively) huge groups at 100yrds.

So can i ask if you measure or know the runout of the rounds you load?

No, I don't regularly measure any more - I did for around 3 years for thousands of rounds. I no longer do, as a matter of course, because I have confirmed 1) I am not introducing additional run out at any stage of my reloading process, and 2) I can and do shoot sub 1/2 moa reliably without doing any culling or sorting of my ammunition based on concentricity, and nothing I do benefits from shooting in the 0's and 1's.

Folks get so axle wrapped on making reloading precision ammo seem complicated and tedious. @JFrank outlined it pretty concisely above - primer ignition, neck tension, charge weight tuning, and jump... Do that, and your ammo will shoot small. Chase the rabbits which get you fed. Concentricity sorting won't get anyone fed unless they're shooting 0's and 1's, and even for those folks, it's highly debated as more voodoo than science. For those 40 and older, we grew up with two tuner knobs in the car - turning the bigger knob moved the needle fast with big results for a little turn, and then the smaller knob only moved the needle a little with small results for big inputs... There are 4 or 5 big knobs for precision shooting, and a thousand smaller knobs, most of them having influence so tiny that a near-zero number of shooters in the world can or do actually prove any benefit from turning them.

 

[Theinkman]

I would be interested in a poll asking how many of us checked concentricity and how many don't . If someone does, what have they seen that makes them believe that is a useful measurement and if their measuring showed rounds that had greater runout than .XXX what if anything they did to correct that. I am not all the way down the accuracy rabbit hole and don't think I will ever get to the bottom of it but have wondered about concentricity for some time. Don't have a concentricity gauge at this time because I'm not sure if I'm willing to take the necessary steps to correct it if needed or desired. My question is does it make a difference?

 

[JFrank]

I posted test videos of two polar opposites.

 

[Varminterror]

I would be interested in a poll asking how many of us checked concentricity and how many don't . If someone does, what have they seen that makes them believe that is a useful measurement and if their measuring showed rounds that had greater runout than .XXX what if anything they did to correct that.

That's the real problem - the burden of proof falls on those making the claim, but few folks making the claim are willing to put the enough rounds down range for the test to prove within the bounds of true statistical differentiation that any observations are meaningful results rather than coincidental.

Directionally, we have videos from 2 different shooters which show evidence to the null hypothesis - that concentricity doesn't influence precision - then a lot of folks admitting we believe it makes a difference, because we believe it SHOULD make a difference... But I know when I've shot my own concentricity tests, I couldn't derive any true differentiation between control and experimental sets.

I wouldn't be surprised if less than 1% of reloaders owned concentricity gauges of any flavor, but I'd be equally surprised to find out if even 1% of those which do own them actually benefit from owning the tool.

 

[zeke]

Yes, as directly stated above - the quality control of producing ammo which doesn't need to be sorted (or fixed) to produce sufficient precision for the task is the game. Then you don't need to worry about measuring produced ammunition as a matter of practice (quality assurance).

The problem, however, stems from the fact so many folks insist concentricity matters for their firearm when it's a factory rifle and their purpose is punching (relatively) huge groups at 100yrds.



No, I don't regularly measure any more - I did for around 3 years for thousands of rounds. I no longer do, as a matter of course, because I have confirmed 1) I am not introducing additional run out at any stage of my reloading process, and 2) I can and do shoot sub 1/2 moa reliably without doing any culling or sorting of my ammunition based on concentricity, and nothing I do benefits from shooting in the 0's and 1's.

Folks get so axle wrapped on making reloading precision ammo seem complicated and tedious. @JFrank outlined it pretty concisely above - primer ignition, neck tension, charge weight tuning, and jump... Do that, and your ammo will shoot small. Chase the rabbits which get you fed. Concentricity sorting won't get anyone fed unless they're shooting 0's and 1's, and even for those folks, it's highly debated as more voodoo than science. For those 40 and older, we grew up with two tuner knobs in the car - turning the bigger knob moved the needle fast with big results for a little turn, and then the smaller knob only moved the needle a little with small results for big inputs... There are 4 or 5 big knobs for precision shooting, and a thousand smaller knobs, most of them having influence so tiny that a near-zero number of shooters in the world can or do actually prove any benefit from turning them.

But in order to confirm your desired "concentricity", obviously you had to measure it somehow? Was not discussing whether to measure and cull every batch, but whether concentricity mattered. And obviously concentricity matters to you, or you wouldn't have confirmed you weren't "introducing additional runout". My reference to "fixing it" was in referral to fixing the reloading process, not individual rounds. And yes i could have worded it better, but pretty obvious from all the posts.

 

[Walkalong]

It would be hard to prove that perfectly straight ammo will or will not out shoot ammo with say .003 run out, so unless it was done by someone I really respected as a world class rifle shot, I would take either results with a grain of salt.

Ever look at the "wailing wall" at a registered Benchrest match? (You know, where the targets are hung up and we go cry over the shots that got away).

If so, look at the wild variations in group sizes, even the best shooters group sizes go up and down. Now, try to be good enough to prove concentricity matters one way or another.

I think straight ammo is a good idea. I also like to take pride in my reloads. And, as already posted, it makes me all warm and fuzzy to know they are straight.

As has been posted, we test dies etc to make sure they don't load crooked ammo, whatever make, whatever it does to a case, we test it. We test it with concentricity gauges. Once we have a known good brass batch/good chamber/good sizer/good expander/good seater that loads straight ammo, we don't need to check much, but I still check a couple in each batch to make sure something hasn't gotten out of whack etc..

Plenty of better shooters than I waxing my butt at registered Benchrest matches who never checked concentricity, but hey, they were better shooters who shot more.

A pro pool shooter using a broom stick could beat my eyes out no matter what fancy stick I might have.

I saved these two targets, shot back to back same gun same shooter same day, I just let one get away on one target. Just a reminder on concentration and how important it is.

 

[film495]

This is a can of worms in itself.

"Clean bore" offset is real. "Cold bore" offset really isn't. If you're moving a goalpost to chase concentricity influence on cold bore accuracy, you're kinda trying to chase unicorns on a flying carpet. The testing would be exactly the same to prove concentricity influence on groups (precision) vs. cold-bore accuracy (confidence in precision such that a correct and accurate zero can be established), it would simply take longer to do the test as the shooter has to wait longer between shots. Not magic, not even difficult, but all signs point to a null hypothesis - unless you own a flying carpet and a field of unicorns.

just to throw out an idea. If someone loaded 100 rounds, and 25 measured .01, 25 measured .03, 25 measured .05, and 25 .07 ... and sets of each were fired in a consistent way from the same rifle, my assuption would be the lack of consistency would show larger groups correlary directly with higher runout, but seems like that is not the prevailing view. Interesting

 

[Varminterror]

I posted test videos of two polar opposites.

Are they?

John's video says in his summary at ~5:45 that his results here with extreme run out with minimal influence downrange should dispell "the notion that you have to be at 1/2 a thousandths," and that these results "should help put a lot of minds at ease."

Bryan's video, even in his video description, states that his results show that "bullet run out up to 0.006" have no impact on precision." Which his Part 2 Video with bullets jumping also shows, and even runs the T test to show that the group sizes, though coincidentally different, are not statistically differentiated.

 

[Varminterror]

just to throw out an idea. If someone loaded 100 rounds, and 25 measured .01, 25 measured .03, 25 measured .05, and 25 .07 ... and sets of each were fired in a consistent way from the same rifle, my assuption would be the lack of consistency would show larger groups correlary directly with higher runout, but seems like that is not the prevailing view. Interesting

I'd actually say that the prevailing VIEW - as in the presumption we all share - is that increasing eccentricity or non-axiality SHOULD result in larger groups, and vice versa, but rather, the prevailing RESULTS shared by actual tests done in this space show that our presumptions simply aren't substantiated in real world results. We ALL think straighter ammo should shoot smaller, but test after test show that for the common run out we'd see in ammunition produced on common equipment, straighter ammo really doesn't shoot smaller, and that we have to go to MASSIVE extremes to actually undermine accuracy with eccentricity.

 

[jmorris]

This really outlines the difference between QC and QA which most folks really don't grasp. Using equipment and processes makes good ammo is Quality Control, which are Lead Measures we implement to do the things which make good ammo. Measuring ammo AFTER it has been made is Quality Assurance, a Lag Measures which determines the result of the process, but does not actually improve the process or product being made.

What I was trying to say this morning.

I’ll admit to spending more time with the tools in the process development phase than in production...

If it’s junk when you are done, you’ve already wasted your time.

 

[Varminterror]

unless it was done by someone I really respected as a world class rifle shot

If it really takes this level of performance to produce differentiated results, then ONLY for that person will the result be differentiated.

Another way of saying that - if a near-zero number of shooters can realize a difference, then a near-zero number of shooters can realize a benefit or a detriment.

 

[jmorris]

Another way of saying that - if a near-zero number of shooters can realize a difference, then a near-zero number of shooters can realize a benefit or a detriment.

Now that’s a quote for trimming 9mm brass...