Some folks have touched on this already. The question of when you start to do triple taps, just to be sure, as you go from a larger caliber to smaller is rather pointless as a reasoned SOP sort of answer. Jesse H and other mention shooting until the target is neutralized. That is really all you need to know. There is no caliber to round count performance formula for you to determine when you need to double tap, triple tap, or unload the entire gun into the person. To suggest that there is a standard would be to over simplify the problem to a point of being irrelevant to reality. There are simply too many other factors involved to make the determination relevant. Things such as size, weight, physical condition, distance, mind set, armor, weapons, etc. all come into play, not to mention your mind set, ability to weild your weapon, ability to hit the target in the necessary vital areas available to hit at the distance the target is from you, caliber, slug weight, slug type, velocity from your weapon at the target, weather conditions, etc.
Given the cailber to shot number, I would guess that you would need to be dozen tapping if using a .22 lr, as a rule of thumb or SOP...unless you are that 84 year old granny in AR who dropped her son in law at 220 yards with a .22 lr rifle, no scope. Apparently, she saw no need in increasing the number of shots to compensate for the caliber or the distance.
By the way and as a serious consideration, drills that emphasize a shot to the head are also overly simplified and hence should not be considered as the great stop shot people think is going to occur. It should NOT be that a shot to the head (as in Mozambique drills) should be the shot that drops the person but a shot to the CNS (central nervous system), particularly the brain, brain stem, or spinal cord above the shoulders. I don't expect people to aim at the spinal cord or brain stem, those are simply alternate portions of the CNS that will more than likely produce the needed result. If you have shot somebody twice in the chest and they are still not retreating, a shot to the 'head' that only managed to damage the face or bone without incapacitating the CNS probably isn't going to stop the guy either. Too many folks get shot in the "head" and survive to quite fine and some manage to continue to fight quite well. Platt and Matix were both shot there, one temporarily incapacitated, but regained consciousness and tried to flee. The other managed to kill two FBI agents and wound others AFTER being shot in the "head" (his face). Mozambique should = 2 to the chest and 1 CNS (above shoulders).
