[toolguy2006]

I recently purchased a Sig Sauer AR10, and naturally started to reload for it. I have been using the "bible load" (168gr A-Max over 40.5 gr of IMR 4895, CCI primer, and 2.8" col), which worked well in my M1A.

The issue that I have been running into, is that occasionally the rounds don't want to chamber all the way. The rounds that don't want to chamber properly usually come back out of the rifle with a shiny spot on top of the case, and the shoulder has a dark ring around it.

The rifle runs factory ammo just fine, and I have compared measurements between my sized brass and the factory stuff, and they come out awful close. I measured case diameter in several spots, as well as base to shoulder (with a Hornady head space comparator). The only real difference that I can find between my loads and the factory stuff is that the factory stuff is crimped.

The sizing die that I have been using is a standard RCBS full length sizing die. I'm not sure of a model on the die, if there is one. My uncle bought them in the mid-1960's, and never used them.

Any thoughts??