I put some more search terms in the site, including "contract for cannon." That pulled up a list including this contract which contains the entire cannon proving procedure that I asked about in another posting recently, so I answered my own question. The proof routine imposed on Lane and Salter of New Jersey in this contract, if I read it correctly, calls for firing two shots from each cannon. The first has a powder charge of 2/3 the weight of the shot, and the second with half the weight of the shot. Two balls are loaded for each shot. That's no small amount of powder, think of it, if you prove a 24-pounder gun, you load in 48 pounds of shot in front of 16 pounds of powder.

Both of these proof shots are loaded thus:

-cartridge with prescribed powder charge in it
-one shot
-one wad
-another shot
-another wad

The cannon is to be fired while resting in a special mounting that will put some extra stress on the trunnions.

There is then another proof by water pressure after the powder proof, and so on.

The description of the proof routine begins on page 8.