I was using russian brown bear ammo from barnaul which has a good reputation. I dont remember what mag I was using. I have the factory 8-rounder some 25-round surefires and 1 fbmg. I know for dure that it wasnt the surefires. By the way, to any who read this, my 25-round surefires have so far been most excellent. I will check my bolt for the problem you mentioned. But I'm gonna hate putting the bitch back together.