If you are shooting a cap gun or a cannon, Center of Mass between the nipples is your target.
Agreed, a head shot is a small moving hard to hit target. A mouse gun bullet in the right spot can stop you right now but the heart isn't that big of a target either so a lot of shots in the lungs to weaken and stop the boogerman is the best bet. Big gun or little, you don't stop shooting till the threat ceases being a threat. If you go for a groin shot aim higher than you think the groin is because that is a small area too and the lower abdomen is a painful place to get hit. Besides your gangsta rapper punk idiot makes it hard to judge where his groin is with their ridiculous low rider trousers. Anyplace below the navel is good but not an instant stopper like a solar plexus or heart shot would be.
Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.