I tried a promag 223 30 rounder out this week in south dakota while praire dog hunting it worked great at first but then it started to feed funny later in the day. Not 100% sure it is the mag as this gun is very modifed but it seemed if the feed lips wore or some thing. I did not really spend time to cheak the issue just switched to my bulgy mags. that once fitted to the gun work fine. They may all fit a bulgy weapon but that indicates to me that the Bulgy must have a very liberal mag well as there was a considerable diffeance in the length of my mags as well as the thickness of the feed lips and area just forward of the lips in the mags I have.