This is an ongoing project at this point. The gun is 1-1/4" diameter bore which technically makes it a 2-1/2 bore, however I've noticed that when you have a gun this big, they get called "2-bore" over a range of sizes.
The barrel O.D. is 2 inches. The stock is still a slab of wood, but the lock mechanism is coming along nicely. The CAD model above has been transparentized to help me visualize how all the parts are going to play together when it's finished. Hopefully I will have 2 of these ready to try out this Spring.
Sights haven't been worked out yet, but will probably be clamped to the barrel in front, and fastened securely to the barrel plug in the back, and yes, there will be some wood under the barrel.
As this is a smooth bore, 1-1/4" lead balls would be the expected projectiles, but in the interest of preserving my shoulder, I'm thinking of making some plastic sabots to carry 1" or 1-1/8" steel balls.
Projects like this fall into the category of "Why engineers should never be unemployed" and currently, my part-time gig has come back on line. The good news is that I'm bringing in some income. The bad news is that the delivery date for these cannons will move out a bit. Not to worry, progress reports will be posted when progress happens.