I thought we were assuming a .22 for the purposes of the thread. In Colorado as well as Utah if someone threatens you with a deadly weapon you can defend yourself and we all know even from that far away they're still a threat. In the scenario I was assuming, a mugging, at that point you have every right to stop an armed robbery of you or anyone else with deadly force. In my experience bad guys, even drugged up bad guys, threaten you first then attack only when it's clear you're not cooperating. I've talked to a lot of assault victims over the years. I agree with you wholeheartedly that the game changes as soon as he is rushing towards you but to me it's two different scenario's. In your scenario my advice is RUN! Do anything to change the circumstances to where he must approach you slowly and you have the chance to shoot at his head from point blank range. A gun, especially a.22, is not a magic death ray it will not insure that you win the fight. I will say this again clearly, the second he is a moving target what I discussed is not an option. The point I'm making is that ANY pistol caliber weapon is marginal against a drugged up opponent. Random center of mass hits may kill him, but whether he dies in time to save you or others is the question. Choose your shots as carefully as you can and remember its better to be judged by 12 than carried by 6.
Gaily bedight, A gallant knight In sunshine and in shadow, Had journeyed long, Singing a song, In search of El Dorado