Hi Dirty Harry Callahan,

Kinetic energy is a huge concern if you're on the receiving end of it. Hence, survival is the only metric that matters.

Avoid, avoid, avoid, and if that doesn't work, run away. Engage only if no other option is available. If engagement is your only option, don't get shot. A gunfight means a bad guy wants a good guy dead. There is nothing beneficial in that for a good guy.

As a predictive index, I'm more inclined to look at momentum.

I would like to suggest caution when drawing inferences based upon what any law enforcement agency issues. A law enforcement agency might issue a 9MM handgun. However, law enforcement agencies generally have lists of approved handgun and cartridges from which their officers can choose. Hence, an agency might issue a Glock 17 9MM, but its officers might choose to carry a 1911-A1 .45 Auto.