“My M-4gery (Rock River AR-14) is great but it did jam once due to me not cleaning it. The tolerances are tight as they should be and any carbon buildup in the chamber could cause a jam. Overall I love the AR-15.
I’ve got the National Match A2 from Rock River. Never a jam. Unfortunately, my M14 can’t say the same. Not really the design’s fault, though.
ALWAYS clean the chamber of any self-loading rifle at least every few hundred rounds. Especially something with a slightly tighter chamber than an M16. (RRA uses Bill Wylde’s chamber specs).