Sherm, I have been loading for the 460 Mag since it came out. I am not a fan of them Hornady 200 gr. bullets. I much prefer the 240 and up bullets. If you go on line to Hornady's site. You can get some good reloading data.
http://data.hodgdon.com/main_menu.asp
Reloading for this round is the best way to get the most out of the 460 Mag. As for loading light loads, I don't do it. I bought the 460 Mag to shoot 460 mag ammo, not reduced loads. If you want to shoot light loads, put a 454 Casull or 45 Colt in it. myself I will grab a different gun.
I don't reload using powder's that do not fill the case with standard loads and powder.
As for cast bullets, 95% of the bullets I shot in all (5) of my 460 Mags were hard cast bullets. Everyone shoots great, and accuracy is every bit as accurate as jacketed bullets. When I can get 1 to 1 1/2 inch groups from a rest at 100 yards with 300 gr. hard cast bullets, I don't think that is bad what so ever. At 150 yards, I can consistently hit a 4 inch clay target with these loads.
The 460 Mag is not just a jacketed bullet gun, and if someone tells you that they need to do some load development.
The bullets I have shot in my 460 Mag and got great accuracy with are 250 gr. 300 gr. and 325 gr. hard cast gas checked bullets from Montana Bullet _orks, 370 gr. Hard cast bullets from Ranger Rick, 240 gr. Hornady XTP Mag, 260 gr. Nosler Partition's and Barnes 200 gr. bullets. Everyone of them has shot great in all of my 460 Mags.