FWIW, I have a DPMS Sportical for a range toy and haven't had any problems with it. Only have about 600 rounds through it, and the only time I had a malfunction was one light primer strike. That was within the first 50 or so rounds fired. All in all, I'm very happy with it.
Planning on ordering the CMMG 300 Blackout upper to use on the lower in a week or so.