After a few 30 rnd magazines are shot and the barrel is smokin hot, the bolt will lock back after the last round. Now I lean the gun against the bench to cool, but as soon as the but of the stock hits the ground, the bolt slams forward. It only does this with a hot barrel. Can't get it to do that when it's cold. Anyone see this happen before? Any suggestions? Is this common? Thanks

Hey Dalusa,  I often times return my bolt "home" by slapping the buttstock instead of hitting the bolt catch release, just quicker depending how I'm holding my rifle.  With that said, perhaps you are striking the ground just hard enough to have the bolt creep toward the ground (deeper into the cycle toward the buttstock) and it disengages the bolt catch.  Just thought about this too.....is the a mag in or out.  My guess would be out.  

Jimmy: Mag is still in. Gun is only held by the fore end. Yea, it with slam forward if I smack the stock also. But I'm not really slamming it on the ground, doesn't take much of a shock at all to slam it forward. Gun is cleaned before firing sessions, I also blow-out all parts during cleaning with 100 PSI air so I don't think it's a build-up of carbon or fouling.

I think next time I'm out rapid firing and the bolt is locked back, I'll try to see if the bolt catch fully engages in front of the bolt or if it's only partially engaged.