I don't think .22 does a great deal of damage to the tissue, but if it won't make an exit wound, this would result in a far less messier crime scene. That's why it can be used for assassinations. An assassin would get close and shoot someone right in the noggin. No need to worry about distance, and penetrating body armor. Wrap the stiff in a bag/carpet and throw in the trunk. Done. No need to scrape brain matter off the walls.