Home Forums Hunting & Shooting Ask The Gunwriters Runout question

Am familiar with the Vaughan and Audette results. Conflicting results are always interesting.

I have tried indexing rounds years ago and did not see where it helped. I found that eliminating or minimizing runout at it source was a better fix for the problem.

Assuming that the chamber is actually concentric to the bore, wouldn't a case have to be neck sized to see any benefit to less than 0.004" of runout? Otherwise, the case is just laying at the bottom of the chamber, out of alignment with the bore.

If one has the case sized correctly (even FL sized - so there's just a hint of resistance to bolt closure), won't the cone-like nature of the chamber and cartridge shoulder center the round as the bolt is closed? Or will it still possibly be tilted? Might depend on the nature of the bolt face and feed style.

Rex

In theory, if the shoulder is not bumped, yes. All ties in with chamber to bore concentricity, bolt face being perpendicular to chamber, and locking lug engagement. All in a perfect world!

Which I believe is why JB stated you see runout having more effect in a blueprinted bench gun. All of those issue should be addressed. Factory rifles, not so much.

Consistency is the key, and if they're bananas they're not laying there out of alignment the same way shot to shot.

I like Eric Cortel and think he gives good advise. Having said that, I do believe that chamber/bullet profile/freebore/brass fit to the chamber all pay a part in the final group size ( as well as other factors) I know that I what I saw on my rifle (that I mentioned earlier in this thread) runout did make a difference. Maybe it was because it was a sporter barrel vs a heavy barrel like Eric has, or one of the other factors mentioned or a combo of factors. Either way, I feel that I want to have as true and straight a round as I can. I strive to keep every at zero but my upper limit is .003 (YMMV)

What tool do you use to measure run-out?

I do a variation of this as Mule Deer wrote about in Gun Gack 1. I use my universal decapping die and then FL resize with the rod a little loose so it can seek the center. It works great. With something like a 22-250 expanding the neck in a separate step would probably give better results due to the amount of body taper.

Another thing to consider is how much the die is sizing the neck compared to how much sizing the neck actually needs to hold a bullet.

This is a little off topic, but I bought a custom rifle a few years ago that came with a suggested accuracy load that had the bullet jammed .01 into the lands like a bench rest load (this is a hunting rifle but the builder does a lot of bench rest work). Does jamming the lands help at all if you don't reduce the neck tension like they do in their bench rest loads? It would seem from the responses above regarding jump that you would need zero run out if you jammed the lands with a neck that had enough tension to feed from a magazine. I never shot the suggested load because I wanted to use a different bullet, but I was curious if it would work for hunting purposes.

A post that is chasing this question down the rabbit hole!

Mr B,
Vaughn reasoned thru the mathematical reasons why he thought indexing should work, then reasoned thru possible reasons why it didn't turn out in his testing. One of the factors he theorized was the ejector tipping the case in the chamber (he used a Remington 721 which is very similar to the Rem 700 mechanically). Audette shot a P64 M70...no ejector to push the case. ...and I'm not sure what the backend lockup of a Mann Fixture looks like, but I thought my surplus Mann barrel was threaded for a Springfield receiver...in which case, no ejector.

There's other things that he chased that are relevant to this discussion such as the tilt in the bolt that the trigger causes (and that he said shimming or sleeving didn't completely correct. And the headspace dim of the cartridge relative to the chamber.

I am very familiar with Vaughan's book, since I purchased a copy shortly after it was published, and have read it several times. He also concluded that his 721 actions bolt lugs and recessed were lapped due to long use!

I read Audette's stuff on indexing quite a while ago, can't remember where.

Run out is often a product of inconsistent necks (thickness), and the best dies in the world will not rectify that issue. I both turn and ream all my brass after its first firing. Helps a lot.

Do you zero your sights for the monkeyed up crooked indexed rounds or the straight ones?

Like you, I had an RCBS die that was driving me nuts, switched to Redding type S and now all my dies are type S and life is simple. ( granted, I only load for 3 cartridges)

There will be the one that claims anything above RCBS is a waste of money, whatever, it’s made it easy for me.

I thoroughly enjoyed (and continue to enjoy) Vaughn’s book! I had probably bought three or four copies after wearing out my first copy and having one or two not come back after lending it out.
Too bad PS is defunct and thus this book is out of print.

Yes, Vaughn found that that his old bolt had the lugs lapped into contact through long use. ...and when he replaced it, he found that the new action had contact on the bottom only...so he recut the bearing surface of the bottom lug to allow the top lug to bear. He mentions that he found the same situation with his three custom bench rest actions.
I remember a well known rimfire benchrest smith described the same situation in front lug rimfires and set out to redesign the walker trigger so that it did not exert an upward force. That was hella controversial and sparked some very heated discussions.

Vaughn’s solution was to cut the bottom lug and bolt face to account for the bolt tilt which showed improvement in both his instrumented testing for wayward forces on the receiver and in his shooting for groups.

Concentricity tool and your eyes.

Actually, just using your eyes works for making sure runout isn't any more than .005--which is plenty for most factory big game rifles. Roll the loaded rounds across a smooth, flat surface and if you can't see any "wobble" in the tip of the bullet, runout is normally .005 or less.