Awhile back, I built a Glock mag 9mm AR, using a Joe Bob Outfitters lower (made for them by New Frontier Armory), NFA lower and bolt, and Ballistic Advantage barrel. I could not get it to feed reliably, especially when using ETS Group mags. Even Glock OEM mags were problematic. I talked to Rudy (Mad_Machinist) at Knob Creek about the problem and he told me he could fix the issue with ease. He quoted me a more than fair price of $50, to include return shipping, or $60 if I needed him to disassemble the upper. A few weeks after 'The Creek,' I sent him my barreled upper and a check for $60.
About a week later, Rudy called me to ask me about some red Loctite residue on the barrel nut, which I'd put on it to keep the rail from wobbling. Rudy was worried about damaging the nut when removing the barrel, though I assured him that if it happened, it would have been my own fault and he need not worry about it. Another few days went by and the barrel arrived back home.
I reassembled the upper that night, put it on the lower, mounted my YHM Cobra 9 can, loaded a few mags from different manufacturers (Glock 15 rd, Glock 33 rd, ETS 31 rd, and MagPul 15 rd) with some 124 gr subsonic, and took it out into the yard to test fire. (As an aside, one of the great things about living in the country is the ability to rip off a bunch of suppressed gunfire at 10:30 without disturbing anybody except the dog.
I only put a couple dozen rounds through it-just enough to test basic functionality-as I'll take t out this coming week for more range time. I didn't have a single hiccup, which is remarkable, considering how often it would jam before Rudy got hold of it.
If you need work done on your pistol caliber AR to get it running right, you'd be hard pressed to find someone better than Rudy to do the work for you.
Thanks for the good work, Rudy.