There's a water-cooled turret cannon that locks the barrel into the end of each chamber like the old Nagant 7.62mm Russiian revolvers. It was made by Augustus Hebert of Malone, New York. I've been trying to find out if he patented it or applied for a patent, since the model is definitely a patent model and the same guy holds a patent for railroad stuff. His railroad patent is 1870 or so, but the multi-chambered cannon patent (if it exists) would be earlier, I would think.
Can anyone find a multi-chambered cannon patent by Augustus Hebert?