I am sure we are reading either the same sources, or quotes from similar sources. Notice no mention of the 2 bore. I have only seen one reference to this cannon, and it was a punt gun used by commercial duck hunters for shooting flocks. Since everything was used or tried in shooting Elephants, and other African Game, I am sure that someone, somehow, used a 2-bore off the shoulder to shoot an Elephant. I don't think this gun's Round Ball would weight 8 oz. but it could have weighed 4 oz. Even out of a fairly short barreled gun, built like a Jaeger, we are talking about a gun weighing 30 lbs. or more. Ever bit of that weight would be needed, I might add, to prevent your shoulder from being broken, alond with the stock. In those days, the barrels would have been iron, not steel, so you would want the barrel to be at least 2 inches across the flats, and probably more. A 30 inch barrel would shoot a maximum of 475 grains of powder in that caliber.
By comparison, Geoge Mitchell's .69 caliber Slug gun weighted 100 lbs. He shot a 2-piece bullet, paper patched, with 350 grains of powder. I don't recall the exact weight of the bullet. However, his 100 lb gun would dislocate or break your shoulder if you did not hold it really firm to your shoulder. And, that barrel was something like 6 inches across the flats. He brought it to my club in the back of his SUV on a 2 wheel cart, strapped to it, and I helped him unload it, take it to our meeting room, and lift it up onto a display rack on a table for our members to view. The False Muzzle for the thing weighed more than 20 lbs! His velocity, BTW, was 1050 fps. measures 20 feet from the muzzle, because putting a chronograph any closer to the muzzle would cause false reading from the concussion waves that hit the screens. At the time, that was the largest caliber slug gun then in existence. someone else has since made another .69 caliber gun like it, and George let someone buy his gun. I watched him fire the thing at Friendship, and it was a trip. Even with earplugs, the blast got your attention, along with everyone within 100 feet on the firing line. He would call out when he was ready to shoot, so that people could pause or leave the firing line and cover their ears.
I served on the crew that serviced a 6 lb. Light field Cannon, and its the only gun I have been around that put out that kind of concussion wave. I would have no interest in shooting a 2 bore, except with light, blank loads. I have bruised my shoulder and rattled my teeth enough in this life to let someone else have that honor with such a gun. :surrender: