I know two guys that survived AK round headshots - one from the low front that gouged a trough above the bridge of his nose into his hairline, he looks perpetually surprised as the scar looks like an exclamation mark, and the other took the round from the rear at a side-to-side angle. It shattered his jaw and took a big part of his tongue. He's disfigured and has a speech impediment, but he's alive.
I believe that the reason we see officers and on occasion armed civilians "overshoot" as judged from afar or the armchair is that no matter how many times they're instructed during training the average joe has been conditioned by popular fiction to believe that in the event they fire a weapon in defense and make a solid hit on their attacker they will observe the individual react dramatically, but no such reaction is likely.
I'd advise anyone interested in the subject matter to get a copy of the VHS or DVD
Deadly Weapons, a tape originally intended to be instructional for LEO's. The video was created by Rich Davis, owner of Second Chance body armor and the inventor of soft body armor.
Among actual live fire testing of many different common pistol, revolver and rifle cartridges there is a section where Rich shows himself and his assistant (ex-S.F.P.D.) testing body armor the hard way - Rich shoots himself twice with a S. & W. model 629 .44 magnum while wearing one of his Deep Cover soft armor under shirt models - with no effect other than to rip up his t shirt, and Rick then proceeds to shoot Alex twice at point blank range with FAL in 7.62 NATO - an absolute full power rifle cartridge - once with Alex balancing on one foot w/ Alex wearing a vest specifically designed to stop such rounds, and the but strikes do not push him to the rear even while standing on one foot.
For a more lethal example, this video (warning, graphic violence) shows South African Police firing on striking miners up close using the local made Galil variant in 5.56 NATO, the R5
http://www.theguardian.com/world/video/2012/aug/16/south-african-police-miners-lonmin
Notice that even with concentrated semi and full auto fire the shot miners are not blown backwards as popular fiction dictates.
I'l tell you from after action interviews with officers who've been through their first lethal force use one of the most common statements is that even though the autopsy shows multiple rounds fired impacted the target the officer in the moment didn't believe they had hit the target
at all until the target drops. Even though (in the case of officers I had trained when they came on the job with out agency) they had been instructed that a living target most often shows no physical reaction to projectile impacts they expected otherwise.
FTR, one of the few benefits from surviving gunshot or other wounds is the opportunity to show off the evidence later - better than any tattoo, and much more expensive to acquire.
