Those Ar-15's would have quite the drop at 1000 yards, its only a .223 round which is one of my favorite Calibers, it would be tough to hit a 600yard target with that rifle let alone a 28foot drop of the bullet at 1000.
I've never fired the AR-15 but i have fired many .223 caliber rifles, its hard to hit those long range shots (using a scope) this is just my experience tho, they do pack a big punch for a .223 round, 2 shots will drop a Moose from 200-400 yards ( it sucks dragging that 1500pound dead body 400 yards
) without any troubles
where i would be hitting that moose at 2.5km with one shot with the 50bmg so deadly.. but we cannot compair a short ranged weapon to a sniper rifles lol