kombi,
The Ruger No1 is chambered and available in 416 Rigby, second-hand in Oz $1300 should get you into one but beware the cost of cases/projectiles and dies. Maximum SAAMI pressure is most likely going to be meaningless, loaded up the 416Rigby will match the 416 Weatherby (same case except for the belt) but you'll never find factory ammunition loaded at this level in respect for the older guns floating about. Besides... the Rigby was made to produce its velocity at relatively low chamber pressures. If your after a big bore thumper that is cost effective, get a 458WM.
Cheers...
Con