Having the .300 Wby in your arsenal, I would say you won't gain much by going with the RUM. If you want a little bit more out of your .300 Wby, you might want to look into the .300 Ackley Improved Magnum. It is basically an Ackley Improved version of a .300 Weatherby Mag. It just adds a little bit more oomph for your money, and forming brass is simplistic and very uncomplicated. You have your smith open the chamber up to .300 Ackley, load new .300 Wby brass as if you normally do, then shoot them. And out-pops fresh .300 Ackley brass. You will have to order a custom reamer and a custom set of dies...Which is the only draw-back. But other than that, there is no drawback.