I guess it depends on the gun, but for a standard 9mm handgun I would aim for the front and directly horizontal to get the prefrontal cortex and the thalamus (pain controlling areas). If you look up online it also says that in close proximity the explosion and hot gas itself can also do a lot of damage. In all honesty, any point blank shot to the brain is probably a garunteed ctb. Rifles and shotguns make it extra-extra garunteed. That's all I know about the gun method, just putting it out there