I use 8 gr Unique behind CP Bullets hard cast 240 for a light load.

23 gr 296 gets a 255 GC Montana Bullet Works cast bullet to 1600 with 7.5 in Redhawk. Same load gets 1400 with 240 XTP. Always use heavy crimp! The cases are Federal from a supply many years ago when they tended to be thicker than Winchester.
Today I go to Starline when new cases are needed.

Have Fun!