@boss_hawg what kind of failures did you have with x39 not firing. Did you upgrade a heavy hammer spring or enhanced firing pin as well.
I have 1 c products defense 30 round mag that has been flawless though i haven’t loaded it past 20 rounds yet.
I have two mags that are 10 rounds (? need to check) that are either asc or cpd that have the misfeeds.
so my issues are mag related.
however with either type of mag you can tell that there is some binding with the tapered case of the x39 ammo. a good tap helps as long as rounds don’t go flying out. it’s hard to explain but i am of the opinion that the x39 is difficult to feed through an ar-15 magwell no matter what setup you’re running. the 5.56 rounds lock in and stays put in standard mags but i would hate to be running around with loaded ar x39 mags in a carrier/belt/vest in a life or death situation. again this is just my opinion and observation with very limited experience with this setup.
just as an fyi - my barrel is a yankee hill 11.5” that i got for a screaming hot deal and my bcg is a toolcraft x39. i don’t think either of these are to blame as long as the mags feed correctly.
i really wouldn’t have built this upper except that the deal on the yhm barrel was too good to pass up (i think i paid $50 on a primary arms listing that i could not find 30 minutes after i completed the deal).
i do plan on deer hunting with this setup later this year but - like i said - this is far from being my go-to if my ass were on the line.