The bolt catch, buffer, spring, could all be suspect. Armalite bolt catches are beefier than the DPMS catches (he could have put an ar15 catch in which is also smaller). Armalite springs are the best ones going for any 308ar, I have several. A great ( no understatement) buffer is one by our site sponsor Clint at Heavybuffers.com. I only run his buffers in my ar's, and they never fail, reduce recoil, and are superbly machined. Here's a link to a thread I started regarding them for some info for you, I hope this all helps. http://308ar.com/forum/heavy-buffers/don't-think-there's-a-difference/