I think it depends on how much elk hunting you plan to do. For a whitetail rifle, I'd use the 7mm RM, but if the elk hunting has any regularity to it, then maybe 300 WM. If it was only elk, moose, no whitetail, I'd do 338 WM. Not that 338 can't be used on deer or 7mm can't be used on elk, but maybe there is something better.