When I first saw the subject title, I thought it was a misprint...usually a gun designated by a weight is referring to the weight of the projectile. With a 17.72" bore, the Armstrong's shell would be around 2000 lb, or 1 ton. The "100 Ton" must refer to the weight of the entire piece. I know the "Swamp Angel" was a "200-Pounder Parrott" of 8" bore. Cool animation, tho...