I have killed the majority of the elk I have killed with a .270 Winchester shooting 130 grain bullets. That being said I have also killed one with a .338 Winchester (35 yard shot
) and my .300 RUM. I never lost a single elk (a couple dozen)with the .270 with the majority of my shots in the 300 to 350 yard range due to where I hunt.
That being said I think a .30+ caliber round gives a better margin for error on elk and moose. My son shoots a .300 Winchester magnum for everything from antelope to moose and I have been very impressed with the performance. Coming to think of it I even killed one of my elk with his rifle and it did very well. My two cents for what it's worth.