…That is not something that you would ever do. Where are those bullets going when you’re not on-target? Even if you don’t hit an unintended target, that’s wasted ammunition, and you aren’t carrying an infinite amount. Trust me when I say that carrying 6 pistol magazines each loaded with 20 rounds, in addition to a chest carrier with 7 fully loaded M4 magazines starts getting heavy.
I’ve done a little IDPA–and will be doing more–and that kind of shit would get you tossed out of a match IMMEDIATELY. If you spend enough time practicing, you don’t need to do that anyways; part of the air marshal qualification course involves drawing a pistol from concealment, and firing a single shot on target-at 7y-in 1.15 seconds or less. High-level USPSA shooters can complete Bill drills from draw in under 2.