You don't even need the "best" bullet. I know people who have taken elk using a .243 and good ole lead tip bullets. My uncles have always used .270's shooting 130-140gr bullets in whatever the cheapest ammo they could buy was, and they have taken more elk than most people will take in their lifetime- in addition to a few moose. My father has shot 150 Remington Core-lokts in his 30-06 since before I can remember, and he has killed a whole pile of elk as well and a moose to boot. I once tried 160gr Nosler Partitions in my 7mm Mag to see if there really was a difference, and to be honest with you, the elk didn't look any more dead than did all of the other elk I took using more affordable bullets. Now I'm back to using 150gr Sierra Game kings.

Just be aware that if you hit an elk in the shoulder, while it won't be able to go anywhere, it might not die right away either. You'll have to put a finishing round into it. Not that theres anything wrong with that. Just something to keep in mind.