A 10-Inch Confederate Columbiad at Fort Moultrie overlooks Fort Sumter

A 10-Inch Confederate Columbiad, cast by Tredegar in 1862, is mounted along the southwest face of Fort Moultrie. It bears on the channel between Fort Sumter and Fort Moultrie - still waiting for the monitors of the United States Navy to try to force that critical passage into Charleston Harbor. The cannon is mounted on a wooden center-pintle barbette carriage. It is marked as weighing 13,360 pounds. Like the neighboring 8-Inch Columbiad at the fort, the elevation mechanism can be seen - explaining the presence of the ratchets on the breech of the cannon.

This Columbiad is one of four such cannon on display at Fort Moultrie. One other is displayed at “Cannon Row” beside the fort and two are mounted on pedestals as “gate guards” near the fort. Four more are on public display in the Charleston area: two at Magnolia Cemetery and two at White Point Garden. Two more are a short drive away at Battery White near Georgetown. (Many more 10-Inch Columbiads were present at Charleston during the war - a few of which still exist, but that is another story.)

The 10-Inch Confederate Columbiad is visually similar to the US Army Model 1861 10-Inch Columbiad developed by US Army Officer Thomas Jackson Rodman - borrowing two of the most visually distinctive properties of the Rodman design: the smooth “soda-bottle” shape that dispensed with the “reinforces” and muzzle swell cast into the shape of cannons for centuries and the “mushroom knob” shape at the breech. The “mushroom knob” was designed by Rodman in response to the weakness of the small, split button cascabels of previous Columbiads when lifting the piece (The Big Guns. pg. 75). Note that the cascabel of the 1857 8-Inch Columbiad of a previous post had been broken off at some point - possibly while having to support the entire weight of the breech during a lift. The photo of US Army troops lifting a captured Confederate Columbiad shows the utility of Rodman’s shape which provides a secure groove for a lifting rope.

Whereas the US Army “Rodman Gun” was cast with Rodman’s hollow casting process which strengthened the cannon as it cooled from the inside out, the Confederate Columbiad was cast as a solid block in the traditional manner before the barrel was bored out.

The Confederate Columbiad is around 13 inches shorter in overall length than the US Army Rodman and therefore about 1,700 pounds lighter - a significant savings of metal for the iron hungry industry of the South. The resource poverty of the Confederacy also meant while the US Rodman was designed for use with wrought iron carriages and therefore has short trunnions of 3.25 inches in length, the Confederate Columbiad was designed for use with wooden carriages and has trunnions which are 9 inches long.

The Confederate Columbiad retained the sawtooth ratchet-and-pawl system for elevation that had been used in the 1844 and 1857 system of US Army Columbiads. US Army 10-Inch Rodmans used a level-post-socket system for elevation which addressed difficulties elevating and depressing the piece when trunnion friction was higher than expected.

Finally, the US Army Rodman was turned smooth on a lathe - something that is best seen in cannon that have been well preserved and never left to the elements in the salt air! The Confederate Columbiad was not turned smooth leaving the cannon with a rougher appearance.

The result was a cannon similar in capability (if not reliability) to the US Army 10-Inch Rodman but better suited to the industrial and resource limitations of southern manufacture.

Along with the 7-Inch Brooke Rifle, the 10-Inch Columbiad was the heaviest and most powerful heavy gun produced in large numbers by the Confederacy. (A handful of very heavy 10-Inch and 11-Inch Brooke smoothbores and 8-Inch Brooke Rifles were produced. Tredegar was attempting to cast 12-Inch Columbiads using the Rodman method near the end of the war, but these more powerful cannon were produced in very small numbers.) As Mike Ryan notes in his excellent paper “The Historic Guns of Forts Sumter and Moultrie” (which once again has been a major source of information for this post), the 10-Inch Columbiad was in great demand as a seacoast gun anywhere that the ironclad ships of the US Navy were active.