In "A History of the Colt Revolver From 1836 to 1940" by Charles T. Haven and Frank E. Belden, the authors list load recommendations from Colt in the 1850s and 1860s.
.31 Old and New Model Pocket Pistols - Conical bullet of 76 grains (92 to the pound) over half a dram (13.5 grains) of powder, or a round ball of 50 grs. (140 to the pound and about .320 inch diameter).
Gatofeo notes: Present day American 0 buckshot measures about .320 inch and makes an excellent ball for the .31-caliber cap and ball revolvers. Cheap too!
The British and Europeans have no counterpart to the American 0 buckshot. Their closest, possibly useable size is the American 00 buckshot of .33-caliber. They designate the same .33-caliber differently: SG (British), SSG (Canadian), B8 (Belgian and Dutch) and Posten III (German). I find no reference to the French having buckshot loads but they must, for hunting and law enforcement.
Keith learned how to load and shoot these revolvers from Civil War veterans when he grew up in Helena, Montana. In 1912, at the age of 14, he began carrying a Colt 1851 Navy in .36 caliber.
Keith recommended FFFG black powder for the .28 and .31 caliber revolvers, and FFG black powder for the .36 and .44-caliber guns.
He didn't list loads by weight, but he instructed to pour in the powder until it almost filled the chamber, leaving room for a greased felt wad and ball.
Keith punched felt wads from an old hat, and soaked them in a lubricant made of melted beeswax and tallow. He doesn’t say if he measured the equal parts by volume or weight.
Gatofeo notes: I use mutton tallow myself, available from Dixie Gun Works. Simply the fat that runs off the meat of sheep when cooked, mutton tallow is the best tallow I’ve found.
This wad was placed over the powder, then the ball rammed down with it until the ball was slightly below flush of the chamber.
Gatofeo notes: I seat the wad as a separate operation, then seat the ball. This provides a better feel for how much pressure I’m applying to the wad, so I don’t crush the powder with too much force. If I forget to add powder to the chamber, and seat a wad, it’s far easier to remove the wad than it is a tight ball!
The above is taken from a posting I wrote and placed on the internet years ago entitled, "Original Loads for Cap and Ball Revolvers."
Search the net and you'll find what Colt and others recommended or used for other calibers, from the mighty .44 to the little .28 Colt.