I knew a police officer who responded to a domestic one night and encountered a drunk and belligerent husband with a large knife. The officer backed through a couple of rooms ordering him to drop the knife, and when he kept coming he fired three times from about 6 feet with a .357 carrying hollow points, probably with a fairly hot load. He later said he could see the rounds entering the guy's 10 ring. The guy stopped, looked down at his now bloody chest and upper abdomen, said "Are you through?" and sat down in a kitchen chair. Of course he fell over and died a moment later, but there was no "stopping power" in those shots. If you want something that will absolutely knock a bad guy down you really need to check with the guys in the field artillery down at Fort Sill.