The load depends basically in the rifling twist rate.
Some revolvers have faster twist rate than others.
In faster twists u need less powder.
For example, I have 2 navy piettas, with different twist rates. I have not measured them, but it is noticeable the difference.
I use Swiss 3f, and the faster twist one prefers 15gr and 17gr the slow twist one.
As wad I use felt wads, and Nivea as lube over the bullets.
I also have an Armi San Paolo sheriff navy with slow twist that loves 20gr Swiss 2f (!!!) without filler and Nivea as lube. This revolver needs .395 balls (.381-.384 chambers...)