It has always seemed to me, non gunfighter that I am, that it rarely, if ever, is about physical speed but rather about decision speed. The one who has already decided is way ahead, time-wise, of the one who is trying to figure out what to do (basic OODA loop). That's why tactics to make the bad guy, with a gun already out, focus on something else, even for a fraction of a second, can be so fruitful as he becomes the one who has to start over.

As I was taught by Keith Jones years ago: Distract his focus, disrupt his plan, disable his body, destroy his will to fight.