i believe the frame of the rb is too small for the s&w 500 mag. the 460 s&w mag will be able to chamber the 45 colt 454 casaull and the 460 s&w.and probably won't be able to be chambered in the rb frame. judging from the recoil of the 45-70 shooting 400 gr at 1700fps i don't want to have antthing to do with such a revolver, BFR will probably be the next revolver to chamber the 500 and 460. if you like a single action