5.7 was mentioned as shooting through vests. The round was developed to shoot through body armor in the Nato environment. The pistol and rifle fired an armored piercing round. Military and police can use that. Civilians can't own it in the USA.
As far as shooting for feet, etc. - all reasonable - that's why training is good for failure to stop drills. I'm just down on those who think this is going to be an easy thing to just take him out. Yeah, the cops in North Hollywood and the FBI in Miami were not as skilled as the Internet League of Lead Slinging Justice Dude. They had a hard time. We cannot assume that we wouldn't and we should be tactically smart and be prepared to die - if you choose to fight (assume you had discretion to leave or fight).
If we start seeing many rampage armored folks - you all better get to the range and take stress based training exercises. In the movie with a J frame - that's one for Wyatt Earp merged with Annie Oakley.
Friend of mine was shooting a P238 as a bug. Nice gun - he is national level and he shot as as well or better than the average competitior. But, we had a stage with a steel popper - hit it to activate a swinger. 9s, 40s, 38s, 45s - all activated it. The 380 just pinged off the steel - 5 good shots and it didn't move. So there you are with armored target and your LCP, Keltec, etc. I got a 380 too. Nice pocket gun, not for guys who think they are mecha.