Marine Sniper is one of my favorite books - I've read it several times. I'll never forget the passage about Carlos sitting on a ridge in the jungles of Vietnam with his .50 cal watching a column of Viet Cong walking along a trail across the valley. IIRC, the quote was something like: "There's nothing more disconcerting than to have the head of your commander explode followed several seconds later by the report of the shot echoing throughout the valley, not having any idea where it came from."
Tends to cause the column of Viet Cong to disperse in all directions in a hurry......
got to try point of impact,you will not be able to stop reading.