Ok here is the deal. There is actually a lot of percision and science that goes into the art of killing someone in the Masterpiece that is war…
Here is why the failure drill was created. You got a twacked out johnny bin laden on pcp and what ever other drug he got pumping through his veins, one shot is not going to put him down, because face it you need to be on something to want to go heads with a Marine rifle squad. So the Marine Corps developed the failure drill to reduce the amount of collateral damage that would come about trying to put down a dude that doesn’t feel anything….
The idea is this, you hit the guy twice in either the chest or pelvic region. The chest because there is a lot of vital organs there, and will cause massive system failure. The pelvic region because that is supposed to slow the dude down or stop him… If the hammer pair fails in either one of those two regions, you put one in his head. Face it without a head the dude won’t operate anymore.