I had a broken in bushmaster shorty that never did feed reliably or even lock back on an empty mag. same story with all ammo especially the weaker 223 stuff like wolf or wwb varmint. In fact i couldnt make it through a 20 round box of wolf without 7 or 8 failures to feed/extract/eject
premium 223 ammo was hit or miss, usually miss. 5.56 would cycle but im not paying for 5.56 when shooting paper. (dont want posts about training with what you use for home defense because i do, but its expensive so when i want to go blasting i take the wolf with me)
tried new gas rings, heavier buffer and ran all the checks i read about on here and determined i was short stroking and low pressure was the reason.
ending up pulling the FSB and opening up the gas port one size. took all of 15 minutes and a wooden block, hammer, punches, dewalt drill and bit. sacrificed a cheap cleaning rod by putting it in the barrel while i drilled since i didnt want to over shoot and hit the rifling on the other side. taking off a FSB isnt as hard as i thought.
i also snipped a turn or two off my mag catch spring(meant to type bolt catch spring). reason being that when i removed the upper receiver and worked the bolt catch with a new empty mag (actually tried it with 6 of them) the bolt catch would not get pushed all the way up by the mag follower. shortening the bolt catch spring made it weaker and it functions fine now.
It hasnt had any failures of any kind and ive put about 1K of wolf through it since then. this has brought new life to a weapon i had owned for a couple years. i used to get mad when i looked at it, now i take it around the house with me and often on field trips in the SUV. it is happy. i am happy. life is good.
hope this helps someone who might have given up on their blaster. once you enlarge the gas port its cant easily be undone though, so make sure its the last thing you do and the problem is not something else.