9mm is fine if you know how to use your weapon. when its you or them, better to fire a volley of generally aimed shots (center body mass, with proper technique can be done without sighting) A well aimed single shot could take as long as blowing through half a magazine. The majority of lethal threat confrontations happen in very close quarters. If you go through a bunch of rounds and only a few hit your intended target (as many a law enforcement agency have proven to be the case) you need to train. a 9mm is still powerful enough to go through multiple layers of drywall and find its way to a friendly.