Thus far all the cannons I’ve mentioned that were in use in April 1861 around Charleston harbor have been “land” guns designed primarily for army use. One notable navy gun appeared in the Confederate order of battle, and was the largest caliber gun used in the bombardment – an IX-inch Dahlgren shell gun. While I have discussed John A. Dahlgren’s boat howitzers in detail, I’ve only brushed the surface of that officer’s contributions to heavier ordnance. Pending that detailed examination, let me offer a brief introduction here.
In the decade before the Civil War, Dahlgren became a giant in the field of naval ordnance, with designs for small arms, the boat howitzers mentioned above, projectiles, firing lockpieces, and shell guns – indeed Dahlgren left no aspect of naval gunnery untouched. The IX-inch gun used by Confederates in the bombardment of Fort Sumter reflected Dahlgren’s work on shell guns.
The theory behind the naval shell gun went back to French Colonel Henri J. Paixhans, who in 1809 demonstrated the effect of “bombs” against wooden warships. The US Navy adopted shell guns with sub-caliber chambers, mixing them on the broadside with full caliber conventional guns loaded with shot. In the 1850s Dahlgren designed a series of “shell guns” intending to place the heaviest possible caliber weapon, capable of firing both shot and shell, on-board the Navy’s ships. This reflected long-standing Navy philosophy to meet potential adversaries with a qualitative edge in ship-to-ship combat.
Dahlgren’s shell guns introduced several innovations over the existing naval guns. Early shell guns used a “gomer” chamber (conical shaped), similar in profile to that used on the boat howitzers. Dahlgren also introduced dual vents (to extend gun service life against vent erosion), strengthened breeching jaws on the breech, and improved lockpiece mountings.
But most significantly, Dahlgren specified a new casting technique. The foundry cast Dahlgren guns in oversized blocks and were directed to ensure even cooling. After cooled, the foundry bore the gun and then trimmed off the excess metal. Although this required approximately 20% more metal per gun than traditional castings, this provided a method to cast large-caliber guns. Dahlgren discovered, much like his Army contemporaries, external adornments weakened the casting. Dahlgren guns used a similar streamlined “bottle” shape, not unlike the Army’s Rodmans (which Dahlgren would later exchange more than a few words over).
Prior to the war Dahlgren designed guns ranging from 32-pdr up to 11-inch calibers. The smallest caliber apparently was not produced in quantity (if at all). But the others entered service from 1856 onward. Keeping with Navy terminology of the time, these were XIII-inch, IX-inch, X-inch, and XI-inch Dahlgren Shell Guns. Particulars for each noted on the table below.
During the Civil War, improved designs arrived for all the pre-war calibers – generally heavier with longer reinforces and attributed to “Bureau of Ordnance” on official notes. Further, the Navy purchased very heavy Dahlgrens from XII- to XX-inch to arm the monitors. All conformed to Dahlgren’s general design principles. Although the larger guns used hemispherical chambers instead of the gomer chambers. Later production batches used Rodman’s hollow core casting technique (with Dahlgren’s conditional approval).
The IX-inch Dahlgren, as indicated on the table, was the most widely produced of the set. Projectiles for the IX-Dahlgren included:
- A 90 pound solid shot with average diameter of 8.88-inches.
- A 78 pound shell (68.5 pounds empty weight) of similar diameter. Shell used a “water cap” fuse to allow over water firing. The fuse would actually burn underwater.
- A 75 pound shrapnel shell filled with 350 balls of 0.85-inch diameter and a three pound bursting charge.
- A stand of grape with eighteen 2.8-inch diameter cast iron balls, weighing a total of 74 pounds. Most surviving “Navy” grape is quilted, and not using the hoops and bolts as with Army practice.
- Canister with 230 1.3-inch diameter iron balls, weighing a total of 70 pounds.
Using a 13-pound powder charge at an elevation of 15 degrees, a IX-inch gun fired a shell out to 3,450 yards.
In most applications the Navy mounted IX-inch guns on broadside mounts such as seen here from the Ordnance Instructions.
Confederate reports from Charleston in March 1861 indicate three IX-inch Dahlgrens within the order of battle. One gun placed in the Point Battery (sometimes called the “Dahlgren Battery”) on Sullivan’s Island bore directly upon Fort Sumter. Two others, mounted on barbette carriages, covered the channel approaches on Morris Island.
During the bombardment of April 12-13, the Dahlgren at Point Battery fired 61 shells at Fort Sumter. Most were aimed at the barbette tier of the fort to prevent firing of guns mounted there. [OR, Series I, Volume 1, Serial 1, pages 41-43] While playing only a minor role in the outcome, the action was the first of many shots fired by John Dahlgren’s guns in the Civil War.
Aside from on site notes and links provided above, sources consulted for this post were:
Olmstead, Edwin, Wayne E. Stark, and Spencer C. Tucker. The Big Guns: Civil War Siege, Seacoast and Naval Cannon. Alexandria Bay, NY: Museum Restoration Service, 1997.
Ripley, Warren. Artillery and Ammunition of the Civil War, 4th Edition. Charleston, S.C.: The Battery Press, 1984.
Tucker, Spencer. Arming the Fleet: U.S. Navy Ordnance in the Muzzle-Loading Era. Annapolis, Maryland: Naval Institute Press, 1989.