When I trained for uncle sam we shot them in the head 2 or 3 times as we wnt by. We would have been in the brig nowadays. The only thing I miss is the budget being picked up by someone else. Only heard yhe 21 feets thing long after I was laying bricks. I still don't use that as a hard barrier distance - the dumb ones may save themselves with me a little closer if they have non brain fart day - idk. The smart ones - 30 feet. And shoot them in the head instead of the knee.