So I purchased a dedicated 22lr upper CMMG, 2 CMMG 22lr mags, 1 ProMag 22lr mag and a plum crazy lower. The thing shoots great. The CMMG mags operate pretty well, occasionally it will FTF, it seems to do it more when the mags get low, 1 to 3 rounds left. I think the follower pushes the round up at to an aggressive angle and it won't feed. The ProMag, SUCKS, it ALWAYS FTF's no matter how many rounds are in it. Over all I happy with everything except the ProMag.
Plum Crazy lower = A+
CMMG dedicated upper = A-
CMMG mags = B+
ProMag = F
Plum Crazy lower = A+
CMMG dedicated upper = A-
CMMG mags = B+
ProMag = F