I' d choose the .270 Weatherby Magnum. It flies as fast and hits as hard as just about anything, and recoil is mild enough that I can shoot it from the most stable position: Prone. It also is rather pleasant to practice with and it doesn' t kick hard enough to make the average shooter flinch, therefore providing maximum power and superior bullet placement.

The 150gr Nosler Partition or similar premium bullet is all you would ever need to kill an elk out to any reasonable range.