Yes & I agree, the .460 would have been "better" perhaps.
There are some good bullet moulds though, in .500.
My .50/95 is currently using a 368gr. FN form a Lyman mould, however they, are .515" in diameter for the .513" groove dia. of the '76.
I am pushing them 1,650fps. not a max. load but close.
Those high pressure loads of the .500 S&W will exceed that, of course by quite a margin. My '76 holds 12 rounds with one in the chamber: that's 1 pound of ammo.LOL