14.9 SOP

But seriously, the best round that you can use is the round that complements your hunting style and the terrain that you are hunting in. It does you no good to have a rig that will drop a moose from 800 yards if you are hunting in wooded terrain or where there is a lot of oak brush and you only have 1-200 yards of visibility. (Turns out that elk like that type of terrain in my experience) Scout out the ground that you are going to hunt and decide on the max range that you are spotting animals. If you are 0-400 yards, .308 or 30-06 are perfect. If you are thinking that you need to shoot further than that you are better off with a magnum, but in all honesty you should be able to close to within 300 yards if you are doing it right.

Most importantly pick something that you shoot accurately. My little brother is a "big man" so he bought a rem 700 in 338 RUM. The gun kicks your ass so bad every time you shoot it that I would take a .243 before I took his gun because I could thread the bullet where I wanted it instead of praying to God that I would have use of my right arm after I took the shot.

Pick the gun based on how much hiking you want to do with it, and pick the caliber and chamber based on how far you need to shoot to take the animal. An elk with a .280 diameter hole through his heart is just as dead as one .338 magnum puncture.