I owned a brass-framed 1851 back in the early 1970s, in .44 caliber.
As I recall, I could only get 25 grains of DuPont FFFG black powder in the cylinder, and be assured of having enough room to seat a ball. In those days, I did not use a greased felt wad between powder and ball.
Chamber capacities can differ, but I don't think you'll be able to get more than 30 grains (FFFG equivalent) of powder in those chambers. The 1851, when made in .44 caliber, has the smallest capacity chambers of any .44 revolvers.
I'd be careful with Hodgdon 777. It is NOT intended to be substituted straight across with black powder, like Pyrodex is. It's fairly strong stuff. The warning to reduce by 15% is a good idea.
I haven't found 777, nor Pyrodex, to be as accurate as Goex FFFG black powder but if it's all you can get then, go for it.
Use a .454 inch ball, instead of .451 inch, whether Pietta or Uberti made the revolver. The larger ball, when rammed into the chamber, sticks to the chamber walls with greater tenacity. This discourages ball movement during recoil.
Also, the larger ball, when rammed into the chamber, creates a wider bearing band for the rifling to grip. In my experience, this enhances accuracy. Certainly, it means better obturation in the bore.
Yep, cap and ball revolvers are definitely addictive.
It's so ingrained in my blood that historical records of the future will probably read, "Lake Gatofeo was formed when the ol' desert cat was cremated and the crater formed by the blast began filling with water ..."