I've used lower recievers from Mega, Aero Precision, Stag, S&W, Noveske, CMMG, LRB Arms, Bushmaster, LMT and Armalite and the only problems I've ever had was a CMMG reciever that would drop G.I mags but not Pmags. Other than that, they all worked served their intended purpose without problems. Marketing, hype, and quality (real or percieved )are all factors that affect the market.