Pyrodex is a volume for volume swap for black. I measured 75 grains of pyrodex R S out in an adjustable measure and then weighed it on my scale. It weighed 55 grains. A 75 grain load with 1 oz. payload would be a good load although case capacity may make for a tight fit. You would need to use a .135 overpowder and probably not much cusion wadding.