I had my first non flawless day at the range today, but not a serious problem at least. On firing the last shot in 12 round mag in a USP .45 the slide closed on a empty mag. Two more 12 round salvos in the same mag functioned perfectly afterword. My guess is that the mag spring might be getting a little age or that the Blazer Brass being of questionable quality may have had a light power load and not fully pushed the slide backward. Any other thoughts?