Turk,
I have shot 10 grains of #5 and the 44-250-K cast bullet (approximately 263 grains). Accuracy was fair at 50 yards from a Ruger SRH. Velocity was at the 1000 fps mark. I have also use Unique with similar results. BUT, if you want to try another faster burning powder, give Green Dot a try. It is now my favorite light/plinking load for the 44 Magnum. I am using it with the same 44-250-K bullet for a velocity of 923 fps and accuracy is right a 1+ inch at 50 yards for 3 rounds. It will generally stay between 2 and 3 inches at 100 yards for 3 shot groups. These groups are all shot from a very solid bench rest of course! Good-luck...BCB