"Wonder if these things are any good at stopping a person."
Ah, there's the catch. It actually may (or may not) penetrate the armor, but even if it does, will it put a person down fast enough to be effective? I wouldn't bet the farm on it. That extra high velocity teeny little bullet sounds like it won't penetrate, unless they have a FMJ for it, and even then the wound channel would be tiny. You'd probably be better off using a traditional SD round and practice the Mozambique.