so I took my mags out this morning after taking some emery cloth to the insides as suggested. No dice! I can run 6 rounds in the mag fine all day. 7 or more and the follower fails to push the next round up. I suspect the strength of the spring (or lack there of) and the fact that the follower can tilt and jam is the cause of this. also spring placement in the follower is an issue as the rounds sometimes keep going primer up instead of nose up. usually a good whack will get it seated better but its no fun when its in the magwell and doing that.
NFA member
I managed to get the KCI mag follower to fit an work with the promag spring. Hugh improvement right off, some minor binding that a little more sanding and lube should improve. The mag and shipping is $30 plus your time to fit everything together makes this a pricy mag. If you can't return them and let promag deal with there product then this might help.
So you can load the mag to full capacity and it feeds? How does the bullet sit? Nose up?
NFA member
The spring guide is welded in the center of the follower, a little tweak to spring and follower guide will get it nose up. managed to get 21 rds in and cycle.