Howdy
About twenty years ago Mike Venturino wrote a series of four books.
Shooting Sixguns of the Old West, Shooting Colt Single Actions, Shooting Lever Guns of the Old West, and Shooting Buffalo Rifles of the Old West.
Some of these were out of print for a while, but I see they are all available on Amazon again.
In addition to talking about the guns, Mike had a loading section for the common cartridges of the era. In the first three he had both Smokeless data and Black Powder data. Cartridges such as 45 Colt, 44 Russian, 44-40, 38-40, 32-20 and others When I first started loading cartridges with Black Powder, those books were my go to for information on how to load the old cartridges with BP. The Buffalo Rifles book is about the larger cartridges used n the single shot rifles of the day, cartridges such as 45-70. This book only has Black Powder data, no Smokeless data.
As I said, I used these books as my reference when I first started loading cartridges with Black Powder.
Or, you could go the tried and true route that I have always used. Fill the case with enough Black Powder so that when the bullet is seated the powder will be compressed by about 1/16" - 1/8". That's really all there is to it. You do need to use a bullet that is lubed with soft, Black Powder compatible bullet lube such as SPG. Regular primers are fine for Black Powder cartridges.
If Photobucket was up and running, I would post a few photos.
I posted a thread a couple of years ago about loading Black Powder cartridges, but since Photobucket is still being a pain in the butt, a lot of the photos are not coming through.
But here is a link anyway:
https://www.thehighroad.org/index.php?threads/shooting-black-powder-in-cartridge-guns.821193/