The .270 Winchester is fully capable of killing an elk. The only rifle that my guide carries is a .270, even his back up gun is a .270. The .270 Win. has an edge in terms of a flatter trajectory and slightly less recoil when compared to the 30-06. But the 30-06 has a very wide selection of bullet weights to chose from. I only mention the 30-06 because it's probably the most popular gun in the field.
If I was to use the .270 Win. I would load a 160 grain Nosler Partition with 51.7 Grains of IMR 4831. This round works very well in my Ruger No.1. I must confess that I'm one of those guys that shoot a gun way to big for the game. But every year I tell my wife that I need a new gun for "this hunt", she buys it and I buy a new gun. this year its a Rem. .375 Ultra mag. I think I'm way over gunned but a new gun is always fun.
Simper Fi
Bill