I'll wager we would have to allow for some luck!
By this I mean the degree of BG incapacitation we might expect - which may be way different from what we might hope for.
Imagine we fire only two COM - one shot traverses the stomach and apart from perforation does little else, misses spine too - bad news for BG but he ain't quitting yet!
Second shot hits close to mid line - lower sternum - too low to hit heart and too central to perforate aorta. BG is still well capable. Spine still intact.
OTOH - of those two shots, one could perforate aorta and second could perforate heart - maybe 5 - 10 seconds (worrying enough) and BG not down but - maybe shocked enough to be in trouble and soon out of the game. Spinal hit too inclusive within those two could also have him down even if not out.
So much would depend on IMO the luck factor as to whether enough damage can be done - we are after all concerned with stopping the threat. This predicates I think the dictum of going to slide lock - rather than 2 COM - ''and assess''. Whether under severe stress a ''lights out'' head shot can even be effectively administered is perhaps debatable too.
So what I am saying is - the sometimes quoted ''2 shots may be enough'' - is maybe not enough at all - and thus some semblance of reasonable capacity is useful.