The effective range for a .308 is about 1000 yds on human sized game. I'm not recommending the shot but 800 yds is well within the capabilities of the .308 in the hands of a marksman with a spotter.

http://www.rifleshootermag.com/featured_rifles/essentials_030306/index3.html

http://world.guns.ru/sniper/sn00-e.htm