if you CAN hit the heart with reliabiltiy, you can also hit the brain, same SIZE target. The heart hit aint 10% as likely to get the instant stop that the brain hit will. NOTHING about damaging the heart causes physical incapactitation, for at LEAST 5 seconds. Nothing about damaging one lung can offer realistic incapacitation for MINUTES. Nothing about damaging the liver or spleen can cause bleeding out incapacitation faster than blowing up the heart. ONLY shock and pain, overwhelming the desire to hurt you, can cause an instant stop, with a chest hit, other than a fluke hit to the spine, and a low hit to the spine can let him still shoot at you from the ground.