Okay, at 1000 yrds its gonna have more power than a .44 magnum point blank range. Like in movies you see a cutsie liitle blood affect in the back of the head. but at that distance the bullet will come down directly on top of you, due to the trajectory, your basically lobbing a bullet up and back down. OK heres the graffic part. the hydrostatic shock that follows the bullet will be soo powerful it will peel you apart. like a banana. you would have limbs flying 20 ft in all directions. So technically it destroys you. it would be alot like a gernade affect from 5 ft away. the funeral would be closed casket assuming you can find all the parts. If you've seen the new rambo movie, he'd on the .50 machine gun, blowing heads off. technically that would be accurate, but from a farther distance it would be catastophic. you realize that a .50 is also used against light armoured vehicles and targets through concrete walls?! As far as power, inside a cannon round it's the most powerfull machine gun and sniper rifle.
The Barret M82 is a semi auto light .50 cal. most snipers of that cal are a bolt but the barret is a remarkable gun for the technology, semi autos tend to be less accurate than bolt. but i know that the M82 can take a lethal shot from beyond 1740yds cold bore.