In my LIMITED research on these baby's... I want one, but I don't hunt right now...
The 460 S&W Magnum IS the load you want. The 45 Long Colt is the "plinking load" out of that baby.
The .460 S&W Mag is the fastest, flattest shooting "non-rifle-cartridge" handgun made. Smith and Wesson claims near-rifle accuracy at 150-200yds, with near-rifle velocities, with rifle weight bullets. There's a lot of info on the S&W sight.
For big game, big bore pistols, Leopold makes awesome durable, and reasonably priced scopes. IMO