Originally Posted by
schnyd112
Could also be brass that may have been fired more than once, has work hardened, and now isn't malleable enough to deform with the chamber when chambered. In other words... the brass may need to be annealed. Get a box of reputable factory ammo and see if the problem persists.
Are you using the mallet to open the bolt, or to move it rearwards? I have had them hard to open, overpressure causing too much bolt thrust, but once the lugs cleared the recess it came rearward just fine.