I own two 300ultramags and have developed loads for one more.I have owned one 300wby and developed loads for one more.On average the 300ultramag will drive a 180gr bullet 100fps faster.If I wanted efficiency I would go for the 308win.If you are considering a 300 magnum with more capacity than the 300wsm or 300win mag you might as well take the extra 100fps that the ultramag offers over the weatherby.I did not consider the 30-378 or warbird because of the price of rifles and brass.