You know, Snippy, my kids say I am a nerd, geek, actually. Affectionately, of course. So I look at that cannon, and can see exactly what was done wrong.
You have to use one chamber for both barrels, not two. Then a precombustion chamber exactly in the center above the single chamber, so you get a good ignition. Make the powder bags out of paper so they break easily, and a ramp in each side of the single chamber to get a good break into the center of the shared chamber. The inner separation between the barrels should be about one inch. Use moderate charges so the chain does not break.
Easy as fishing.
Still, conventional chain shot from a single barreled piece would have worked better. You want something that would have really worked, build a real plant to make barbed wire, and another to make Maxim guns and cartridges. Gatlings are too big, too heavy, and too hard to make.
Morning Iris7.
I just figured load both barrels with grape or canister instead of using a chain.
Yeah, but you're their geek. LOL, and one of ours to. The Foxhole is full of them. ;-)
I figure that at least it was a good thought, the age of invention is fascinating. You have to admire great minds, minds that aren't lazy but put to good use, even if an idea doesn't quite work as thought.