I use 80 gr of pyrodex P in my gun with a 460 gr paper patched bullet.
You said your putting on a Lyman 57 sight. My question is why are you going to use only one sight in point???
The 57 is field adjustable so you can have a 50, 100, 150, and a 200 yard mark. When you use a range finder and get the yardage you set the sight to that yardage and hold dead on. I have been doing that for years. Ron