At what point does cartridge runout erode accuracy?

[Idaho-Lefty]

I WORRY a bit MORE about,.. the freakin',.. WIND !
*** But, I WON'T shoot any of my .270 WSM Bullets with, OVER, .006 to .007 Maximum TIR for,.. Hunting Elk !
Too Important and fug's with,. MY "Confidence" in, my Ammo ! I use the worst one's for, Foulers & Playing at, Plates !
My Forster Dies, Produce, very FEW,. "Bad ones", anyway !

 

[NZ_Fclass]

It's as much as what we do, as why we do it.

Do we take sub-standard rifles or ammo to the range knowing that part of our set-up is faulty? Do we waste time and money making banging noises just for the hell of it?

Shooting can be expensive, and we are not all in a position to buy the best and latest - but given whatever budgets or other restraints, we endeavour to shoot x's. We do this by getting the best barrel and action we can, the best scope, rings, trigger etc. put together by a decent smith ( or clever mate) that can make the combination work.

We also strive to use the best ammunition that we can obtain. Most presses and dies are capable of making good ammo.Any half-decent press will form a reasonably straight case, provided that the die is held well and there is sufficient slop in the shell holder. Most dies from Lee, RCBS or Hornady are quite capable of turning out a good case - I quite like Lee collet dies - straight necks can be achieved, well under 2 thou run out. But I can do better by setting neck tension, so I use Redding and Forster, and I'm moving toward using expander mandrels. I prefer to full length size. I don't use cheap brass, preferring Lapua or Norma for neck thickness consistency without neck turning. I anneal the brass - because it makes better, more consistent ammo.

So is it a matter of "has to be under 1 thou runout" or simply part of the process- a holistic approach to getting things "right"?

And I will make a confession - it took me a while to learn the difference between pistol and rifle reloading (I'm a slow learner...) I made "A" grade in ISSF centrefire using a Lee turret, and later a Dillon, churning out a couple hundred .32 S&W rounds in an hour on a Saturday. Cases got cleaned every so often. Loads never varied, Runout's not a thing. And at international level - the top guys use factory ammo anyway.

 

[Longtrain]

When I first started in FTR with a 308, TIR didn’t mean much to me having come from XTC and never paid any attention to it.

My TIR was usually high 4-6 or so. I learned to sort my brass and turn necks and my TIR dropped below .003 for most cases. Tried to shoot 1K with .001 or less, as my learning curve for LR was budding it was impossible to determine if the TIR made any difference.

I moved to a Dasher in Open Class and my cases are mostly .001 or less. Don’t know why, its a no turn Lapua chamber, fire formed cases and bingo great TIR. I guess it matters to some point in the scheme of shooting LR. I chauk it up to one factor that I don’t have to worry about in 1K shooting. Can I quantify a specific result on paper, no, I can’t, just part of the making the sausage.

 

[mikecr]

I believe runout matters when it reaches the point where the banana you're chambering binds against the chamber. A new pressure point.
I doubt bullet pointing errors matter.

 

[AWS]

when your accuracy won't come up to your standards and the only thing you can blame is runout.

 

[D-4297]

This got me thinking ; so I grabbed a box of 100 rounds I had loaded for a Match I didn't get to shoot , and checked twenty or so . Average TIR was .001 - .0015 . They went to the range last week , and gave me a very nice 200 - 14X at 600 yards , in 3 to 5 mph breeze . Second relay was a 197 - 12X . I guess it matters to some degree , that you are loading concentric ammo . Or at least consistent concentric ammo .

 

[XTR]

“

This got me thinking ; so I grabbed a box of 100 rounds I had loaded for a Match I didn't get to shoot , and checked twenty or so . Average TIR was .001 - .0015 . They went to the range last week , and gave me a very nice 200 - 14X at 600 yards , in 3 to 5 mph breeze . Second relay was a 197 - 12X . I guess it matters to some degree , that you are loading concentric ammo . Or at least consistent concentric ammo .

I think most of us make ammo with similar TIR, assuming you don’t drop any of them

if I drop one it becomes a sighter.

 

[Mulligan]

“

I think most of us make ammo with similar TIR, assuming you don’t drop any of them

if I drop one it becomes a sighter.

But, does it matter?
Will the dropped round shoot into the group?

 

[Webster]

I have searched the web, cannot find a good study or really any solid information on the relationship between straight ammo and accuracy.
Is there a correlation between small groups and really straight ammo?
Does building concentric ammo help with accuracy? If so, how much matters?
CW

I know nothing about the subject. I always thought that traveling down 24 inches of barrel would straighten it out. It's a swaging operation, the rifling squeezes grooves into the bullet. My only question is does hitting the rifling at a very small angle permanently deform the bullet. Just size and seat the way Tony Boyer does and quit worrying about it.

 

[XTR]

But, does it matter?
Will the dropped round shoot into the group?

There comes a point where it probably matters more in my (our) head than the target, but that is also probably equally important

 

[clowdis]

Runnout cannot be more than your chamber clearance. In other words, if you have a chamber that has .003 clearance all around then the worst you can do with your ammo is .003. If you chamber a round with .005 runnout it will have to conform to the .003 chamber. Neck and throat clearances can be even tighter.

 

[liljoe]

I like the statement above, just size and seat like Tony does. If you only knew the lengths he went through to get straight ammo and everything else perfect.

Joe Hynes

 

[Shinbone]

Whether runout matters depends on how well your rifle shoots. If it shoots 2" groups, then the difference between .001" and .005" runout won't matter. If the gun shoots .2" groups, then going from .001" to .005" runout can make a difference.

 

[Dgd6mm]

Whether runout matters depends on how well your rifle shoots. If it shoots 2" groups, then the difference between .001" and .005" runout won't matter. If the gun shoots .2" groups, then going from .001" to .005" runout can make a difference.

Has anyone tested and proved this ? Or is it a theory?

 

[Mulligan]

Has anyone tested and proved this ? Or is it a theory?

That was (is) the original question.

I cannot find it if there was a good test done. So is the tester keeping their results quite or maybe it really hasn't been done?

CW

 

[mikecr]

I like the statement above, just size and seat like Tony does.

Finding best shooting CBTO is a whole lot more important than runout concerns.
And that is NOT usually seated into lands with hunting capacity cartridges & LR bullets.

 

[seymour fish]

There are a lot of potential variables. One is long throated barrels with tight freebores and heavy for class high BC bullets. The combo doesn’t allow much for runout, they will straighten the bullet in the bore when you load them. In short flat based bullets that short range BR shooters use, maybe that is a different animal.

About 10 yrs ago an old BR shooter was at the range with me, this guy was a forever tinkerer/tester. He told me that in his testing that he could not see any difference on the targets with less than .009 runout. I haven’t checked runout since then. I shoot F class, my worst bullets have less than .005 and usually had .003 or less. Most of us should be in the same boat with good equip and technique. There are enough other things I can spend my time on.

He was correct. FTR at 1000 there is no difference up to .005 whatsoever, and some minor opening around .009

 

[Phys86]

Oh my God. Really?

I've been agonizing over this since I started using some new Redding dies a couple months ago and have worse run-out than I used to with my Lee dies. With those, I'd usually get 0.001-0.002 tir, and an occasional 0.003. With my Redding, I'm getting a wider range and a lot more at and above 0.002 with a couple 0.004.

I mean... My reloading the last couple of weeks has been more stressful and aggravating than enjoyable due to this. And you guys are telling me it doesn't matter much below 0.009 and no difference below 0.005?

 

[mikecr]

At some point it will matter, but 2-4thou is not the end of the world unless your chamber is tighter.
I wouldn't stress out over it.
But there is an opportunity here to learn. What is causing the issue? Just figure it out and fix it.

 

[Dave M.]

I have searched the web, cannot find a good study or really any solid information on the relationship between straight ammo and accuracy.
Is there a correlation between small groups and really straight ammo?
Does building concentric ammo help with accuracy? If so, how much matters?
CW

This may not be the answer that most people want to hear, but I’ve always wondered the same thing so this year I did something about it. I loaded up 350 rounds of 6 dasher identically and after I was done I measured each and every one of them using the 21st century concentricity gauge. I selected the worst 150 rounds for bullet TIR, 5mm in front the tip of the bullet. They ranged from 0.0035” to 0.006”.
I brought them to a two day 1000 yard F Class Open competition and truly expected to score horribly. My personal best at 1000 yards is 973-34X. The weather, both days, was very similar to other times I had shot at 1000 yards at this range. I ended up shooting 966-30X. That’s less than 0.7% reduction. Not that significant. However, in all fairness; I feel like I could better answer the question if I had shot the 150 rounds that measured the best for a true comparison.
Dave