I had a look through my loading book for the loads I used in my 458 when I had it, I used the following loads.

All in winchester brass and Winchester LR (standard) primers.

30 grains of Alliant 2400 and a 400 grain RCBS cast bullet gave me 1450 fps.

45 grains of AR 2205, same 400 RCBS = 1675 fps.

48 grains of AR 2207, same 400 RCBS = 1625 fps.

I don't use filler of any sort with any cast bullet load.

DC