Cashman, that's why I like the .460 over the .500, .45 colt, .454 casull, and .460 S&W.
Some people will get onto me here, but I have been reloading a really long time, with loads not published anywhere for competition. Both lighter and heavier than normal in a given caliber.
I would start with trimming the .500 cases to .45 colt length and then use .45 colt data for the starting loads with the bullet types and weights your talking about, they will be lighter than advertised due to the increased case volume, but I think you can start with the hottest loads. You revolver is rated for 50,000 psi +, 15 to 20k psi ain't going to hurt anything. You will get into trouble using the full length case with reduced powder charges, case density in a case so large is a real problem. Squib loads would be common, and accuracy would suffer a lot.
Start slow, and look for all the signs, primers backing out, not enough pressure, primers flattening, too much pressure. I would start with fast burning powders like red dot, bullseye, ww231 with a standard primer, mag primer might work better but this is developement. I would put a really hard crimp as well.
.500 cases are expensive, so How bad do want to do this? It is no harm in saying this is a bad boy and I really don't like it, in full house mode, trade it for a .460 and you probably won't be out any more money than trimming expensive cases. Just a thought.