they ALL can be a problem. I have a 1903 made in 1906, and an original (obvious not "original") with two tone which hung up, and I had to file on back wall (and i think rear of feed lips) to get it to fully insert, lock, and slide work. Same thing with one of two Triple Ks tried, the other worked perfectly. Whatever you end up with, if problems, look for bright spots up top and lightly file/fit/file/fit until it works. The factory mags were hand fit to each gun, at least in the early days. I use the Triple Ks with flawless function, now, fyi, and use as a carry mag.