Gatsby - Smoothbores are very short ranged guns. 100 yards is a bit too far for most all smoothbores. I was talking about rifles.
I have shot 545gr. round balls at 1,550fps from a 7 3/4 pound shot gun using black powder as the propellent - 7 drams it took to get that speed. I would under NO circumstances shoot such a load from an antique, let alone one with an elongated bullet of even greater weight. The gun I used took only 2 shots to break the stock into two pieces. After repairing and reinforcing the stock, it absorbed many more of those 'load's, but I quickly dropped to smokeless powder, which kicked about 1/2 as much- or less.
In order to get 1,550fps with black powder and a 730gr. slug, you'd need almost 9 drams. THAT took a very special 12 bore, I think, not a light weight paradox.
I'm fishing here, as I lack the experience with paradox guns, but do have some personal experience with large bore slug and ball ballistics, recoil, and what it takes to get results.