Hello Ferrgie. Hey I know you may have your mind set, but just wanted to throw this in the mix...
When I was looking for a load for the 460 S&W, I was advised to try H110, and I'm thankful I did. I ended up with a load that will shoot sub MOA with a 300 grain XTP MAG pushed by 40.5 grains of H110. And to make it a little more inticing, I know that this same load, give or take .1 grains, has worked for several people with the 460. Its my favorite round, and seems to be a "sweet spot" for the 460.
Enjoy the revolver, its one of the great ones IMO.