There is a ridge on the inside of the frame. I think I started out with a file and removed a little on each side and continued to test fit. I then went to a Dremel and did the same. Once I got all the mags to drop freely, I went back and cleaned up with a file again. It's not pretty, but I don't notice it at all. Again, this is what worked for me and the whole "New vs.Old" debate is something I just chuckle at now whenever I see this come up. This just seemed like the most logical and simple fix. I had no intention of putting Mags in a vice, squeezing here and squeezing there, trying to "tune" a mag that should work,in my opinion straight from the factory. I knew that once I started trying to modify mags, the "warranty" went out the window, and the chances of me screwing up brand new mags was MUCH higher than me screwing up the frame.No mag catch hole mod either. Being in California, these mags are like gold. Hope this helps