Also, BTW, I get a higher number of malfs, failure to feed, and double feeds in my S&W 5.45x39 AR than I do in my MSAR 5.45x39!!
Yep, I have one of the 12 to 20 factory guns, and yep I shoot it although only rarely because of the pain of cleaning corrosive ammo, the AR has NP3 so no worries.
Then I dont know what the issue is, me and several members have killed barrels on these 5.45 uppers with little to no trouble. From personal experience they are gassed as much as a Colt 6920 since Ive shot them back to back on the same lower. What buffer are you using?
I had the same issue and solved it with an adjustable gas block, I was sprayed with gas for the first couple shots and then dialed down the gas input since the block was already present on my build.
Try Ballistol (straight and water mixed) for that. Haven’t shot much chlorate primed ammo in awhile, but the stuff makes cleaning Pyrodex fouling a breeze now that I switched to it. Dissolves any type of projectile jacket fouling I can think of also.