FWIW-
There's a gunsmith in Germany making a limited run of revolvers in ......get this.... .600 Nitro Express! They have a spare barrel and cylinder in .458 Win Mag. The weight is around 19 pounds. I have a poster of it somewhere. It was given to me by my German friend Michael "The Kraut" Uekoetter (a nickname he gave himself, btw). I'll ask him to post here about it if someone wants more info.
For the record......I would never pull the trigger on that thing! I'm a recoil-hating p*ssy and I don't care who knows.

this should be under the .458 Win Mag handgun thread. (????)