Along the line of this thread on capacity. I suggest that people read Ferfal's blog "Surviving in Argentina". Go back through his posting and search for the shoot out in the Radio Celebrity bedroom. Three bad guys already given all the hostages had ie cash, watches, flat screen televisions etc.etc. Still not enough as the bad guys were going to rape the women. Thinking their all dead the Radio guy feigns a heart attack and falls down. Retrieves a hidden Glock .40 and comes up shooting. The hostage son also gets a hidden a .357 and enters the fight. The end result is one bad guy shot 8 times in the chest and is dead right there. BUT IT TOOK EIGHT ROUNDS (.40 cal.), another BG wounded and flees to hospital for wounds, one runs away un-harmed.
However, the Radio guy shot is up severely, hit 4 times, leg bones protruding from wounds etc. But keeps fighting. Son shot 2-3 in the buttocks/stomach and is critical. The good guys won but both wounded, all the women unharmed. The point of my retelling this is that the good guy's fired well over 20 rounds in that bed room. They had no place to run, no cover apparently. Just "toe to toe" and shoot till you --- or them, are dead.
Capacity may not be everything in a confrontation, but it would seem to be GOOD thing to have in a lot of situations. All this is written from memory so read it for your self on Ferfal's blog. Your mileage may vary.