Yep, check head space to start,

Next check the ammo (loads or reloads), and what you have have the gas system/ tension spring-buffer set to for the ammo, which  brings up back to ammo.   Since it very easy to go with a slow burning powder that although will have normal working pressure, drives the gas pressure at the bolt unlock higher to cause the bolt to unlock sooner (more residual pressure in the bore during faster bolt unlock, which means harder pull out of the chamber, and more gas to to spent primer during the pull that can cause the primer to be blow out on the unlock/spent case pull) and if you are using a slower burning powder, may have to decrease the gas to the B/C to slow the bolt unlock back down.

So really, take a good look at the spent case rim from the extractor pull that might be bending the hell out of the rim on the bolt unlocking too fast, and the sides of the case for a rough to dirty chamber that is marring the hell out of the shiny spend cases, and go from there on the solutions.

Check headspace... and what specific ammo ( s ) ?