I don't know if this will help you or not, but I ask that question of a powder manufacturer (BULLSEYE) when I was trying to work up a load for a 100gr. bullet. This is what the guy told me. You can use the least amount of powder that you want as long as you can get the bullet out of the barrel without sticking it. So, I was shooting a 38 special 100gr. DEWC using 2.5grs. of BULLSEYE. IT WOULD POUND TACKS......................CookE