Everything was going fine after shooting about 100 rounds with my P01 then I had a problem, a round failed to feed properly, the slide was stuck halfway. I cleared it and after that all went well for the rest of the session. I have fired thousands of rounds with this gun and this is my first experience with this problem. I know that is a very good ratio but it still left me with a bad feeling for obvious reasons. It was also the first time that I was shooting Winchester ammo from Wal-Mart, was it the ammo? The mag? I don't know, anybody have advice?