I took my latest 9mm AR to the range yesterday and kept having doublefeed and stovepipe issues:
My initial thought is to polish the feed ramp and check the extractor - any other items I should check? The build is:
CMMG MK9 lower
PSA 10.5 upper & ramped bolt
KAK tube, PSA 9mm buffer weight, milspec carbine buffer spring
CMMG Milspec LPK
Colt style 32 round SMG magazines (unsure of MFG - one is labled "Brownells", the other "Palmetto State Armory.") I was able to repeat the malfunction with both magazines. I was also only loading 5-10 rounds per magazine.
I was using bulk Remington UMC 115gr 9mm FMJ ammo. The ammo was giving my Sig Sauer P938 some extraction issues (the extractor failed to grab 2 out of approximately 100 or so rounds I fired at the same time, my CZ75 SP01 ate all of it without issue) and the Sig will normally eat anything. I can't see the ammo causing the double feed issues, however.
Thanks in advance.