I did a similar thing on a stage, was a 2 string stage, 6 targets, 1 round each, mag change one round again. First box went fine .... moved to the second box and forgot to put a fresh mag in my pistol at the start of the second string. 1,2,3,4,5, slide lock (WTF), mag change, 6, mag change, 1,2,3,4,5,6. Man I was pissed the RO looked at me and just said "Im glad that you changed mags again or that would have been a bunch of procedurals". I learned, make sure you put a fresh mag in and not one youve shot out of.