My cast alloy is about Lyman #2 although at the moment have Winchester hard shot in ingots but it needs a bit more tin I think to cast properly.
Eagle , The Win hard shot is more likely to have an antimonial and or arsnic hardening and I would be more inclined to cut it with Pb and with your sizing to .425 should stand up to the 63gn 2209 quite nicely and be similar to my 50/50.