I am thinking the problem is likely the first round chambering softer than those during gas powered cycling. Single loading some groups may tell me something. A good push on the forward assist is worth trying. A call to Rock River is next.
It's probably not a stress relief problem because it does the same thing hot or cold or shooting fast or slow. If this barrel was on a bolt action it would probably be very accurate.
Montana Man, rifles can't count, but they react to differences in bullet pull, vibrations, cartridge concentricacy, and various other mechanical dynamics.
