Actually, as long as you have properly dimensioned bullets and cases, the amount of black powder pretty much is self indicated. You need enough to fill the case to the point of being lightly compressed when the bullet is seated, but no so much that you can't seat the bullet.
As Jim K noted in a message several years ago, that's about 10 grains of 3F black powder.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.