Welcome to the Forum.
Regarding your Browning Mountain rifle, you did well! They were well made and good looking. And, good shooting.
From what I gather, they were rifled for patched roundball. The load recommended by Browning was 70 - 90 grains of 2F or 3F powder behind a .438 - .445 patched roundball. Target load would be 45 -50 grains 2F or 3F.
That's a start. Experiment to find what she likes.
And read up on this Forum...go back through the list of old topics for loading and cleaning info. (That'll have your mind spinning!)
Take care of it, be safe, and, most of all, enjoy!
:thumbsup: :hatsoff: