My suspicion is that...

by mcassill, Saturday, July 11, 2015, 18:34 (3427 days ago) @ rob

the change in brass (to Remington) hiked pressures enough to push a weapon that was already somewhat overgassed over the edge to where it had extraction problems. In this case it isn't chamber pressure that's the important detail so much as pressure at the gas block. As Miles has suggested, a heavier buffer may help. An adjustable gas block might as well. Or you can stick to loads that the rifle demonstrates that it likes.