A few weeks ago I shot about 100 rounds of Double Tap 180g to make sure it would cycle consistently as it's my preferred defense load. Twice, about halfway through a 15 round mag, the slide locked back. The previous shot extracted fine, and it continued functioning after I released the slide. Unfortunately I wasn't keeping track to determine whether it was the same mag or not, but I've shot many rounds of normal 180g TMJ target loads through all of my mags and never had a single malfunction. Any thoughts?