Re: AR 9mm magazines for Colt
My understanding is that C-Products makes crap and that the company is no longer even called C-Products. The best bet are the magazines made by Metalform that Brownells sells. They were the "official" Colt magazines back in the day.
Personally, I am stuck with pre-ban original Colt magazines or converted Uzi magazines. Both work well, except the Uzi mags don't hold the bolt open without a mod.