Here's some food for thought.

A .50 caliber gun shooting round balls over 85 grains of FFg Black Powder gets something around 1550 fps at the muzzle. That's works out to about 1020 fps at 75 yards (with 433 ft.lbs. of energy).

If the load is reduced to 70 grains, muzzle velocity will be about 1450 fps, and velocity at 75 yards will be 990 fps (with 409 ft. lbs. of energy).

So, going from 85 grains of powder to 70 grains reduces the powder charge by 18%, the velocity at 75 yards by only 3%, and the energy at 75 yards by only 6%.

To add to the dilemma, the trajectory for the two loads will be almost exactly the same, differing by less than half an inch.

Change the load to FFFg, or to Pyrodex, or to Triple seven and you get progressively higher muzzle velocities with an 85 grain load. But the reduction ratios work out about the same if you reduce the charge of each of those powders to 70 grains.

I know all this. So why do I still use loads in the 85 to 95 grain range in all of my round ball shooters.