Numerous times while I was at Smith and Wesson during my instructor cert. We used a timing device for the shooting and had one of the guys in the class do the running. 21 feet is also the widely taught number in the Navy as the "survival gap". I was a security instructor for my last three years in the Navy and taught quite a few classes. I'm pretty confident about my own skills with a sidearm. Inside a room with the weapon in the holster, me vs. me, I'm saying the knife gets first strike. I'm not saying me with the knife doesn't eat lead, but I am saying me with the knife gets the first strike. I say I'll come out the winner against a guy with a gun because I honestly believe that I can't be beaten in a survival situation. Maybe I'm deranged, but that's what I believe. In any case, if you have the room at your range and a timing device, try it out. You'll be amazed.