Remember, gents, this rifle was rebarreled in 1891 with steel barrels so could have a faster twist than we would expect from an 1870s BPE rifle.
The 3/4 dram increase in charge makes me think lighter in the bullet weight but with those barrels, could have very well gone to a heavier charge and a heavier bullet.
A chamber cast or some fire formed brass would be near to see to ascertain whether the bullet is supposed to be bore or groove diameter.

I ogled that rifle for a long time...
Glad somebody here has her now!