With a solid solid, I don't think you'd need a second shot on that elephant - provided, of course, you hit where you are supposed to. With practise, and enough of an energy absorbing recoild system, I think the bolt would rack plenty fast enough - given the right incentive.
; I've not heard of the .450 Rigby. The case base is virtually identical to a Wtby. Where'd you think WTBY got the measurements for his .378 from? John Buhmiller gave him the idea to neck it up to .458. Old John called it simply his .450 magnum and said it was too fast and penetration was reduced, even with Kynock solids. He cut the speed to 2,200fps and called that the ultimate. WTBY, of course, had to push them as fast as possible and keep the pressure up over 60,000PSI.