Recently purchased a new armalite super sass and with much load testing I've been able to get consistent .50-.75 size groups from this rifle when single feed. The problem is that when feed from the mag the groups open up to 1.5". So tonight I loaded the mag and manually ran them through the rifle and checked bullet seating depth and this did not change, I use a crimp. Also rechecked run out, also no change. But when I measured the shoulder it had been set back .005". When loading for the rifle I measured a spent case and bump the shoulder back .002". Does anyone have any idea what would cause the additional .005" set back when the bolt rams it home? Can't help but to think this would causing my problem. Thanks in advance for your input.