Posted by Alk8944.
"DO NOT even think about using 8 gr. Unique with a cast bullet. Alliant, and previously Hercules, has never listed more than 6.8 gr. Unique for a pressure of nearly 34,000 PSI. To increase the load to 8.0 gr. will increase pressure by ca. 35%, and that is for single-base powders. Double-base powders, as are all Alliant pistol/shotgun powders, is a completely different matter. If you want/need higher velocity then use 2400, it is the propellant used for initial cartridge development of the .357 Magnum in the early 1930s, and still cannot be improved upon for full power loads for this cartridge."
Well now my old Lyman cast bullet manual shows a max load of
Unique of 8.0 grs with a 158 gr gas check cast bullet at 35,500 cup.
My old Hercules manual 1-84, shows a max load of Unique of 8.5 grs
with a 158 gr lead bullet at 36,500 cup. Never is a long time and I
think calculating pressure increases based on powder characteristics
like single base or double base might prove dificult. I agree 100%
on the idea of switching to 2400 for full power loads. The money
already spent on the can of Unique is gone, don't worry about it.
Just buy a can of 2400 and load away.