I'm deciding to join on this a bit late, but here's some recently developed thoughts I have. Currently, I've been on the Trauma Service at a hopsital in downtown Detroit. On my patient list, at this exact moment, I have 10 patients with gunshot wounds. Over the last 3 weeks, I've seen probably close to 50 patients with gunshots.

People I've seen survive:
shots to the head (including those that penetrate the brain)
shots to the chest
birdshot
buckshot
multiple (10+) gunshot wounds

So, based on these 50 or so encounters, I've decided that it's not number of shots, or caliber, it's SHOT PLACEMENT. The ONE person that's died on my shifts had a head wound with brain material coming out. In contrast, I have 3 patients currently with head wounds that are not dead, including a person that took a hit in the forehead. The take home message is, in a SELF DEFENSE SITUATION A) hit what you aim at, B) aim at parts that stop the person (you don't always have to kill) and C) shoot until they stop. Many of my patients kept running after being shot multiple times. Someone could easily run to you, not away.

Again, idle musings based on treating lots of shot people.