Hmm.
Here's what you found with your one "experiment":
"I decided to measure bullet runout on some of the Lapua match ammo and to my surprise it was .003 to .006. I decided to buy a Redding bushing neck sizer die to see if results improved. I used a .336 bushing and sized about 2/3 of the neck. Concentricity also improved to consistently under .0015 bullet runout.
"The results were improved accuracy without flyers for this gun. I've bought a few more of Reddings FL bushing dies for some of my other guns and have also seen some improvement in the little amount of shooting I've had time for in the last couple of years."
Am puzzled about how you came to the conclusion that the improvement in accuracy was due to more consistent neck-tension in your handloads rather than bullet run-out--especially when "concentricity also improved to consistently under .0015"--especially during "the little amount of shooting I've had time for in the last couple of years."
I've shot a couple thousand rounds with the 308 rifle I mentioned. Accuracy was better after switching to the bushing dies even though my concentricity was already within the .003 limits you have mentioned. And the very accurate factory ammo was less concentric than these limits.
Do you think improving concentricity by .0015 is the reason for better accuracy?
Or could it be something else?
