IMO if you can't do it with a .338 Win Mag, you can't do it with the Weatherby or RUM version as well.

If you truly want more power I'd suggest you look at the time honored .375 H&H magnum.

akbound is correct.....the Weatherby and RUM versions are not only longer, the RUM is a larger diameter as well.....and will require feed rail work and a smaller magazine capacity.......something few serious hunters are not keen about.