Just returned from the range and had mixed results. I ran 60 rounds of Armscor M855 through: soft shooting, good accuracy, but had feeding issues regularly. It would string together a few and then not feed and few. Never had ejection issues. Initially it was stopping short enough to not cycle the trigger, but by the end the trigger would cycle but the carrier did not go back far enough to get behind the next round.
It has a flat wire spring and I may trim it before fiddling with the gas port.