Well, Ive read this post since I got my Colt 1911 reproduction model I bought four additional 'off the shelf' Colt type mags. Along with the two that came with the gun, I went to the range. WELL, three of them would not lock back the slide, two of them would not drop constantly and so, after about 500 rds of ball FMJ ammo to get the gun warmed up I came home and bought 6 new M'Cormick mags from Brownells. Put the four in the junk drawer and the original two I packed up in the box. Nuff said