NONYA: I too have seen some strange things happen with bullets and both human and animal skulls. Some bullets never penetrate, others amaze me. I have seen 158 gn rn 38s from a snubby at contact range on a suicide attempt penetrate the skin but slide right around the skull and out the other side. Seen similar happenings with animals. I assisted two men in RVN who were shot right through the heart, one with a grease gun and the other with a 9mm, and I am certain stranger things have happened.
However, I have also seen one fatalities with the smallest of calibers. The impact point of the bullet has a bunch to do with it too, but without getting into biological specifics and discussions on skull construction I would opine that 22lrs are absolutely minimal for personal defense which would kinda leave the 17s somewhere else. JMHO. Mikey.