.308 Concentricity

[Knife Edge]

Just bought the Hornady Lock-n-Load Concentricity Gauge

Some of the rounds are spot on at .000" runout, been dialing everything else down to .001". Am I being overly anal considering this is for an AR platform? Is .002" to .003" just as good?

Lastly, I assume there is some runout as I must be pulling them off the Redding 2400 trimmer improperly, probably torquing the neck as I pull it off the pilot.

[huckberry668]

I did that concentricity thing for a while and didn't find it much help at least for my ARs. I measured several boxes of Federal GM 308 as well as Blackhills, Remington and Hornady factory match grade ammo and they're all within .001" to .006" runout. All shot under .75MOA out of my Savage heavy barrel.

I used Federal GM brass, trimmed, square off the primer pocket, debur the flashhole, turned the necks. I separated the loaded rounds by .001" runout and shot groups with each lot. Not much difference and we're talking an Armalite AR15T (24") that gets under .75 MOA groups consistently. I often wonder how runout readings affect accuracy and those who swear by it.

I guess within a few thousandths maybe negligible. Or ultra accurate guns benefit more from low runout.

My experience is that, it's impossible to load each and every round with .000" runout. However careful I am I always get between .001" to .003" runout for most of my reloads. I did find that if you seat the bullet little bit at a time (3 to 4 times) and rotate the brass each time it'll come out with less runout discrepancy.

[brian01tj]

Unless you're a true competitive bench rest shooter don't bother with it

[30Cal]

I stopped measuring. Mine are 0.006" on average and shoot like a house on fire.

[brando]

Runnout is an important issue, especially with precision rifles, but most people will not see much of a difference as long as you're in the thousandths. For a while back in 2007 I was having runnout issues with my .408, regularly getting 0.008" which made even low ES loads shoot no better than 3MOA @ 1200m. Getting it down to 0.002" halved my groups at that distance.

[Knife Edge]

As usual, you guys provide the real deal. Thanks and glad you are here on Calguns!