Bullet runout or concentricity

[jelenko]

I've tested up to half of that variation with no real advantage on an F class target.

What I find so hard to wrap my head around is how a chamber and throat need to be withing 1 TENthouthanths yet we can feed it ammo that is miss aligned 100x that tolerance and it doesn't cause major issues.

I think the throat aligns the bullet when chambering it.

 

[markm87]

The neck sizing may be to blame. I've shot .007+ runout factory ammo with SMKs and they shoot fine, but I personally wouldn't accept that slop in my loads.

Neck bushings both floated and tightened down gave me the worst runout. I went to Body dies and Lee Collet neck dies to get it down to +/- .001-.002 or so.

I do use the Wilson seating dies too so I never even have to check runout anymore.

 

[Doug Casner]

Runout govt. spec. was .005 at L.C. but that was for a M60. Tried to get the match and special ball better. I gotta believe straight necks are more accurate. Line it up with the center o f the bore. If it starts out crooked it aint gonna get any better. Doug

 

[McStocks]

Sitting at the loading bench a few years back and for some reason rolled some loaded rounds across the bench. The bullets looked like little bananas wobbling in the brass! I thought, "Holy Crap, we better not shoot these in a match!". Then I looked at the box, and realized it was the ammo that my shooting partner, Shirley, used in the Long Range matches at Camp Perry! She was the only one who cleaned both of the 1000 yard matches the first day - 400, bunch of Xs. I subsequently replaced the dies though.

A quote from Boots Obermeyer: "Do you suppose a bullet squeezed down a barrel with 50,000 PSI behind it remembers that it started out a little crooked?"

Steve

 

[Doug Casner]

Steve, your probably right., but why the govt. spec on concentricity? I used to have war with some of those taper presses trying to get them in. It was kinda hard getting some of those old machines, new in the 40s,to run straight cases. I hate to think my work was for nothing. Doug

 

[gdbleb]

Lots of great experienced-based advice above.
But its winter and nobody's punching many holes in targets outdoors so we're in the shop.
You should trace the runout through all of the steps in your reloading process - 1) neck runout of fired case 2) neck runout of resized case 3) neck runout of loaded round/case 4) bullet runout of loaded round.

You'll learn a lot.
Stay warm.

 

[seymour fish]

Have you shot those .007- .008 and see how they shot compared to the .002, you maybe surprised.

Perfect to .003 show no difference at 1K, ,,.005 and above do in a system capable of 2.25” 5-shot groups

 

[SKWERLZ]

Your runout more than likely isn't your seater. More than likely your sizing process. Unturned brass could add .0015 to your runout alone on case neck.

The biggest source of runout I found in my process was regular dies with a pull through neck sizing buttons.
Pulling the buttons and using a Lee collet or mandrel was a marked improvement.
More so on dies that sized down the neck excessively.
The one honed neck Forster with the button I tried was pretty good actually.

 

[L.Sherm]

More so on dies that sized down the neck excessively.

This is the case in my experience with non- bushing FL dies

 

[Doug Casner]

You guys are right. I was remembering through the cobwebs off my mind. The govt. measured concentricity on blank taper too. I wonder how accurate that blank was with .002 neck concentricity? Doug

 

[McStocks]

Steve, your probably right., but why the govt. spec on concentricity? I used to have war with some of those taper presses trying to get them in. It was kinda hard getting some of those old machines, new in the 40s,to run straight cases. I hate to think my work was for nothing. Doug

Doug, Like I said, I replaced the die that was causing the problem - no sense starting out crooked if you can fix it! I suppose the paper-pushers have to make up a spec on everything. When I shot M60s, all I cared about was that they fed and went, "Bang"!

 

[Coyotefurharvester]

Has anyone tried chambering a round with 0.005+ runout in a chamber with 0.002 neck clearance. My guess is it will have less run out after extracting with out firing. Don't know as I never saw a need to measure runout as I usually FL size without bushings.

 

[Jonnyofalltrades]

But what about in a factory cut chamber, that has more like .005"+ of radial clearance? Maybe the canted bullet thing actually matters then?
Every time I read about a test it always involves a rifle with a custom barrel that I can assume is a lot tighter in the neck area than an average Joe's factory rifle.

Perhaps I'll have to try this out for myself.
As an average Joe, I have access to such rifles.

 

[Wild Bill IV]

No runout at all would be ideal. Wouldn't perfection be great!

I am not sure what the least acceptable runout should be. I have only recently purchased a gauge and the runout I got on my latest 308 Win loads ran from a low of .002"(4 out of 15) to .007-.008 for the rest. I think that is not good.

I am using Lee dies. I think that a better bullet seating die would go a long way toward correcting my runout problem. If so, what bullet seating die would you recommend ?

I am using Winchester Match Brass.

Any die that has the spring loaded sleeve alignment will work!!!

 

[Doug Beach]

.0005” total clearance is pretty typical for the freebore section of a match reamer. If your chamber has freebore, and you’re seated out anywhere near the lands, your bullet is being aligned by the freebore diameter. Will it stay straighter if you remove it from the chamber? Probably not.
Can it be multiple thousandths out of alignment at the moment of truth? Nope.
Factory chambers are a whole ‘nother beast.

 

[6BRA]

A bullet locked in the freebore with .007 or .005 runout, has to create unequal neck tension. Although straightened out with the bore. When the big bang occurs I don't see this benefiting anything. In the way the brass expands and neck releases projectile. I'll pass.

 

[searcher]

I think the throat aligns the bullet when chambering it.

Yes sir. I think jamming the bullet eliminates most runout - and is likely why most guns shoot best jammed - if not a contributor to accuracy.

 

[Webster]

A bullet locked in the freebore with .007 or .005 runout, has to create unequal neck tension. Although straightened out with the bore. When the big bang occurs I don't see this benefiting anything. In the way the brass expands and neck releases projectile. I'll pass.

A lot of assumptions. A lot of top long range shooters say it doesn't matter? What's the opinion of the top short range competitors? I make my decisions based on results and not this is what I think is happening.

 

[BoydAllen]

A lot of assumptions. A lot of top long range shooters say it doesn't matter? What's the opinion of the top short range competitors? I make my decisions based on results and not this is what I think is happening.

The best way to resolve this sort of question is to test, with an accurate rifle, with good conditions. Without testing, opinions are not of much value.

 

[barefooter56]

Perfect to .003 show no difference at 1K, ,,.005 and above do in a system capable of 2.25” 5-shot groups

Per Fred Sinclair " if your bullet runout is .000 to .005 you dont have an issue. The big thing is to ONLY USE A FIRED CASE to check this. Like has already been mentioned : Check the case : right out of the chamber, after sizing the case, and after seating a bullet ( probe should be as close to the bullet /case mouth junction you can get it without touching the case).
Issues like this can sometimes be fixed by centering the decapping rod, loosening the grub srew in the lock ring to let the die "float" in the press threads and help with centering of the die on the case, checking to make sure the seating stem is centered in the die, ETC. THE RUNOUT WILL TELL YOU WHICH DIE(S) are causing the issue.
easy peasy.