I like the behind the shoulder shot because I love elk meat.
But if the elk is quartering away from you and you want to put it down fast "look through" the elk and see where the off-side shoulder is. Shoot it in the "other" shoulder, and with a Barnes X or a Nosler partition and most heavy weight bonded bullets, the elk will fall at the shot of VERY soon thereafter. The bullet wrecks the lungs first and then breaks the bone or traumatizes the muscles close to the bone.
If the elk is quartering toward you shoot the same place, but at the shoulder that is closest to you. It breaks the bone and then destroys the lungs.
Same result.
