Here's another thought that I'm sure will rile up a few people here. If the gun I'm shooting has allowed me to practice that much and get that good and the bad guy in front of me has a short range weapon (knife, club metal bar etc.) do I need to kill him? On my worst day at self defense ranges I could keep all six shots inside of a quarter with my Ruger.
Legally, it does not matter if you aim at his upper center chest, at his cerebral cortex, at his pelvis, at his kneecap, or at his right big toe. In EVERY
case, when you use a firearm, you are using lethal force.
Morally and practically, the law is written that way because any time you launch a bullet at someone, you run a strong risk of either killing them or crippling them for life. This is true even if you aim at some "non-essential" body part and hit exactly what you aim at.
If you are not at peace with the idea of killing someone who is trying to kill you, then carrying a firearm is not for you.