The OP is originally looking for: "Any recommendations on a rifle calibre that would suit? Something that can go down to a 250 or 350gn projectile with mild loading for general use but can be bumped if if i ever say hunt water buffalo or draw a MT grizzly tag (great odds on that im sure!)" Many people who have used normal hunting calibers(eg .308) refer to anything over that as large bores. For what he wants the good old 375 H&H is slap bang just what he needs. If he needs something a bit bigger the 404 Jeff and 416 Rigby will offer all he needs. The performance difference between .458 Lott and .458 Win. Mag is summed up in Frank C. Barnes's Cartridges of the World, Sixth Editionas such: "The .458 Winchester is advertised as developing 2040 fps with the 500-grain bullet, fired from a 24-inch barrel. In practice it doesn't actually do much better than 1900 fps. The .458 Lott will do an honest 2300 fps+ from a 22-inch barrel." As for the 460 Weatherby capable of firing a 500 gr bullet at 2700 fps, well what the hell you wanna hunt with that! The rifle will beat you to submission before you finish your hunt. It is a piece of crap as a hunting rifle, especially for use on DG. I had a client give me a 460 Weatherby he had specially made for a 18 day safari. He had to use a spare 375 H&H I had in camp to complete his hunt as he could no longer hit what he was aiming at when using the 460 Weatherby. I declined the offer and had a highly upset client. I finally screwed the barrel off and kept the action and the stock. and he seemed to accept that but was not sure what he would do with the barrel that I gave back to him. Amazingly you don't appear to have anything good to say about the 458 or the 460 and with only about 400 fps between them with the same bullet your objectivity ....in my opinion...is somewhat in question. Nothing to be amazed at, the 458 WM does not achieve what is was originally designed to do and the 460 Weatherby is way too much gun even for an experienced hunter. Both are poor choices as hunting rifles and even more so when choosing either of them for DG. There are many better choices for that job. To clear up the objectivity part.. well it is quite simple. Recommend a caliber that the OP asked recommendations for not the two most extreme apart calibers that fall far out of the scope of what the man is asking advice about.