At 1,000 yards and a .338 Lapua Magnum, or the .300 Win Mag, he has less than a second to move. And the sound of the shot won't get there until 2 seconds later.
One second could mean the different between killing and maiming when you’re talking about hunting game. As an ethical hunter, I will never take a shot I know will maim, and up to this point in my life, every kill I’ve ever made was instant. I’ve only ever had to track a boar, and that kill was made with a bow.
If you’re talking about a human being, that 1 second could mean the difference between killing a combatant or alerting him/her. You maim a Taliban fighter, they’re going to continue to fire that SAW unless you sever their shooting arm.
Also, how about moving targets? That sort of ballistic magic doesn’t exist except in the mind of a trained sniper.