Once you get into that bore size it just really doesn't matter. Anything you hit with it will be dead. My personal favorite is the .450 Alaskan on a Browning '71 frame but if I was going to build it again I'd probably go up to the .50 Alaskan. If you're dead set on a bolt gun I like the .416's, especially the Rigby and Weatherby (just because I'm partial to Weatherby actions, not necessarily for the round itself).