Unique is one of my favorite powders for my cast lead bullets. It seems to be accurate for a lot of different calibers I've tried. Examples are 357 mag, 44 mag and even 308 winchester. When it comes to 308 win between 13 and 15 grains using 130 to 150 grain cast lead bullets gives me very good accuracy using my TC Compass bolt gun.

For 357 mag and 44 mag in a lever action you get decent velocity which usually increases the efficiency in terms of kinetic energy per grain of gun powder used. Many bottle neck calibers like 223 or 308 loaded with jacketed bullets pushing at or near their typical factory loadings for velocity only give you around 50 ft lbs muzzle energy per grain of gun powder used, but a 357 mag or 44 mag 16" carbine using unique powder can give you around 100 ft lbs muzzle energy per grain of gun powder. That's twice the kinetic efficiency.