when yo load 20 rnds. in it does it still hang up? or is it only when the mag is loaded near capacity? I have some old Scherer 40 rnd mags I had to use a jizz wheel on and open up between the feed lips. You may want to install a Wolff extra power recoil spring first. Some of the PMI 40's when new and loaded up near capacity will also hang up until you get down to 34-35 rnds. Just make sure it's not something else before removing material from the mag. If someone else you shoot with has a Mini you may want to let them try the mag and see if it acts the same in there rifle. By the way what brand magazine is it?