not a sniper. this video has made its rounds on the net. most have it saying that its a .50 cal taking out taliban in afghanistan. one of the posters had it right, it's a hunter picking off some small animal.
You're exactly right - it's not a sniper video. It's rock chucks (whatever they are) being shot out West somewhere. I once tracked the original down to a hunter website where it was described for what it is.