While you can shoot 45 Colt and 454 Casull in a 460 S&W Mag, I understand accuracy with at least the 45 Colt is not as good as it could be due to the 1/2" shorter case and the jump to the forcing cones that the bullet has to do.
While I have fired a few 45 Colt cartridges in my 460XVR, I found a light load (1100 fps or so, light for the 460
) for the 460 S&W case. That way I do not have to deal with the carbon build up in the chambers that forms when shooting shorter cases.
Besides, I save my 45 Colt cases for my 45 Colt revolver and the option is there if I choose to exercise it.