Gotta agree with the Doc. Bull moose aren't deer, but they're sure as hell not like hunting cattle. You can screw your self out of a moose very easily. Most shots are under 100 yards and I'd hate to be the one toting a .50 BMG out of the bush. I've killed several with my 30-06, 1 with my bow and hope my next one will be with a spankin new 45-70.
Brett - Build the rifle and THEN discover the need for a new moose shooter.