577 T Rex = As what 500 grains said

500 A2 = Buy a used 460 Wby Mark V and with luck it will come with dies and cases. A simple rebarrel and recoil lug installed on the new barrel. The Mark V 460 stock is more than big enough in the forend for a 50 calibre barrel.

But shoot the 460 first with the muzzle brake removed and then see if you really want more

Mike