Except that way you won't get the same psychological effect and subsequent decrease in unit morale that you get from killing a guy from 800 yards.I would argue that a 50 cal. rifle is for long range shooting regardless of what the target is. Its primary function would not be killing. I can think of much easy, more efficient ways of killing someone than to shoot at them from 800 yds away.
It is extremely stressful on a military and probably even terrorist units when their guys just drop dead and no one knows from where the bullet came and when the next one will drop the next unlucky guy.
Snipers exist in armies for a reason.