From everything in I've gathered from the .50cal groups ,the problem is he's using a SLAP round. Due to how they function their not supposed to be fired though anything with a muzzle break or supressor, due to problems with the sabot case getting caught can and causing excess pressure. Not to mention SLAP's have a much higher pressure naturally than other type of ammo. Barret, and most of the other 50 cal manufacturers highly advise against using SLAP's . And honestly when you can get API and RALFOS rounds makes you wonder why you want SLAP.