The Marines refer to the site on an M-16 as an "onion ring and fry." The idea is that you want the "fry" to bisect the length of the "onion ring" through the radius, setting your radius upon your target. We had a briefing on this that was very specific about the analogy (As an aside, it seems the Marines begin every brief with a history lesson, underscoring that every Marine should know his history. That reason contributes to why Marines carry themselves so well. They know where they came from).Every Marine is first a rifleman, so each Marine is expected to qualify as a riflemen. We were taken into a rifle simulation room where there was a platform holding rifles and magazines at one end of the room and a screen at the other end. The screen projected four targets, with circles on the target where the heart and head should be (Four people at a time could shoot. The rifles and magazines communicate with sensors the hits on the target). We were taught the "Groucho" stance and were instructed to raise the rifle halfway, then full on the target, aim, and then shoot.
A Marine explained to me the lack of wisdom in hitting your target only once. The M-16 leaves a puncture wound, of course, but the body will compensate for the wound by rushing blood into the hole to stanch it. "Double-tapping" or, better yet, hitting the target three times in a combination of head and heart insures that the body has no sufficient blood to stanch three vital wounds. Marines are scientists when it comes to war.They had us shoot downrange with the wind blowing towards us and to the east. We were told to shoot to the left of the target to counter the wind. It worked. 
By the way, the nice man shooting to the left of me is a great shot with 6000 acres in his Tennessee backyard to practice. The brass shells of his bullets kept smacking me in the left temple. Oh, they scanned us with metal detectors to make sure we weren't taking any brass shells out with us. Evidently, a while back some Marines personally made over $150,000 by reselling brass shells. Marines are also businessmen of war. Hahaha. Brilliant.
