While back I posted on a problem. a AR10 in .338 jamming when feeding from the right side of a magazine
After trying various things, handed the barrel to someone with the right tools. He checked the headspace(correct), and gave the chamber a good polishing. I finally got it back and reassembled it yesterday.
After some cycling tests with dummies worked, fired it today. Only about twelve rounds, but kept topping-off the mag so it would be feeding from the right for the first half-dozen, and zero problems. Looks like that was all it needed.
Right side feed presentation malfunctions (FTFeed) are often:
* bad feed lip geometry of the magazine
* Sharp ejector that catches the side of the case rim (This will manifest as a failure to go into battery)
* Improper alignment of the magazine with the feed ramps in one or a combination of any of the axes, due to tolerance stack