I've got one that does it w/ LC .308 & Chilean 7.62x51. It's aggravating the hell out of me. I have thoroughly cleaned it and every 4th shot or so, I get a stovepipe. I've checked the extractor and it seems okay to me.
Thoughts?
Extractor spring
Buffer spring
This gun has one battle pack run thru it. This problem started at approximately 150 rounds. I have scrubbed the chamber and am wits end.