Quote Originally Posted by YFZsandrider View Post
When slamming the mags home, try to recognize if there is a difference between pushing straight upward, and pushing more at a 45 degree angle toward the front of the gun when driving the mag home. Its far more likely to occur when driving in a upward and foreward motion.
A lot of guns will do this, especially if you use a forward motion as described. Some guns, like the HK USP, will do this more frequently than others, but it can happen with any.

I've been told in a Glock armorer's course that Glock didn't intend for the slide stop lever to be used to release the slide, but only to lock it back. A more European practice, which is also why the slide stop lever is so small.