Gunpowder burns very quickly. When it does, its transformation from a solid form into gas is accompanied by a lot of light, sound, heat and force that disperse all directions. To use the force element to push a projectile in a single direction requires corresponding resistance to channel the force into that direction. Surrounding it inside an iron tube does that nicely. In the early days of artillery, iron wasn’t as strong as its potential, so to contain (and direct) the force of the gunpowder, LOTS of iron was needed to surround it. The more gunpowder used, the greater was the resultant force, so the thicker the surrounding iron had to be.

During the American Civil War, the largest-calibre weapon available to the Union/Federal Armies, was the 13” seacoast mortar. It used 20 pounds (@ 9kg) of gunpowder to hurl a 220-pound (@ 100kg), 13”-diameter (@ 330mm) shell over 4,200 yards (@ 4km) away, in spite of its relatively-short length. Cast in a Pittsburgh foundry with a very-thick wall, it weighed 17,120 pounds (@ 7765kg), which dictated that it be moved by, and fired from, a railway flatcar or ship.

‘The Dictator’ was the most famous of them all, because it was photographed so many times (and we humans STILL photograph the biggest, baddest, most-impressive stuff around). Served by Company G of the 1st Connecticut Heavy Artillery Regiment, it first went into action on 9 July, 1864 by lobbing shells into the city of Petersburg, Virginia and at the Confederate Chesterfield artillery battery on the other side of the Appomattox River, from a specially-reinforced railway flatcar. In-service till September, it fired 218 rounds. The fate of this famous gun is unknown, though it was probably quietly sold as scrap iron after the War (though replicas do exist).

The internet is singularly unhelpful on the outside diameter of ‘The Dictator’ (the model scales-up to 1.085m in diameter x 1.26m in length), the number of them produced, or what the shells were filled with.