You might also try locking the slide back, inserting the loaded magazine, and then pushing the release lever down (or pulling the slide back a little more) to load a round in the chamber. This is also a good way to introduce the loaded magazine into the gun in normal firing situations. After the last shot, the slide will lock back. Drop the mag, insert another, drop the slide and commence firing. You don't have to apply as much pressure to get the magazine to seat as you do with the slide forward.