All of the factory .416 Rigby's I know of, are on long actions and expensive rifles.

In the .416 Taylor, a 400gr. bullet driven by 70-odd grains of powder is preferable to me and my current recoil sensitivness over a 400gr. bullet driven by 100-odd grains of powder for the same speed. Guess I'm a bit soft in my old age.
I know that in North America on even the big bears, nothing past 52gr. to 58gr. of powder driving a 350gr. or 400gr. bullet at 2,000fps to 2,100fps is required. Hmmmm sounds quite similar to the .450/400, doesn't it.