Here is an update, after reading Wallhanger's suggestion, I had another look at the 20 and this time I reached in from the bottom and pushed the carrier in simulating loading a shell, then I used my finger to push it away from the shell latch, which it did. After that I was able to cycle shells through with out a hitch. Pretty strange but at least I don't need to file it and I know just that much more about the gun. Thanks for your feedback guys!