In part 1 of this set, I discussed the background and design evolution of the boat howitzers. Then in part 2, I focused on the carriage designs. Now in this part I turn to the variants within Dahlgren’s system of boat howitzers.
When considering operational requirements for the boat howitzer system under development in the late 1840s, Lieutenant (later Admiral) John A. Dahlgren noted, “The weight of pieces intended for boat service should never be so great as to be burdensome, whether carried in the bow or stern….” Thus the draft and free-board of a ship’s boat governed the weight of the howitzer. But Dahlgren continued, “The boats belonging to the several rates of ships vary materially in their capacity and structure, and hence arises the necessity for pieces of different weights.” (Dahlgren, A System of Boat Armament, p. 20). Under Dahlgren’s system, with variants off a standard boat howitzer design, offered bigger guns for bigger ships.
The boat howitzer system, or family as we might call it today, initially included three types (Dahlgren, p. 22):
- A 24-pdr howitzer of 1310 pounds for use on the launches of 74-gun Ships-of-the-Line, or as needed the launches of the large frigates.
- A 12-pdr medium howitzer of 760 pounds for use on launches of frigates and smaller boats from the Ships-of-the-Line.
- A 12-pdr light howitzer of 430 pounds armed the launches of sloops, and any small boats which could not bear the heavier cannon.
All three were bronze weapons following the same form including a hemispherical breech, near perfect cylinder around the seat of the charge, then with the exterior gradually tapering to the muzzle. As mentioned before a loop on the underside replaced trunnions. A bracket supported the lock-piece to fire the howitzer. Internally, the howitzers used the gomer chamber specified in the design. One difference for production weapons over the original designs, however, was the knob and breeching loop. Earlier I used this illustration (as it offered eye-catching color) to back up my description of the breech end of the howitzers:
Note the threaded section at the very end, taking the form of an eye loop, was to engage the elevating screw. A breeching loop, complete with pin and block separates the elevation screw from the breech. However, during tests Dahlgren determined recoil force was minor and dispensed with the breeching loop. Production boat howitzers conformed to this (less flashy) illustration:
Production of the boat howitzers began in 1849, with the first, a 12-pdr light howitzer, going to the sloop John Adams. Production remained slow, however, as the Washington Navy Yard remained the sole production source during the pre-war years. Even with expanded facilities, the Navy Yard could not keep up with demand. So during the war, Cyrus Alger and Ames Manufacturing produced additional boat howitzers to the Dahlgren pattern.
Confusing the nomenclature somewhat, the Navy’s Ordnance manuals referred to the 12-pdr medium as the 12-pdr heavy. This does not appear to be a model change but rather administrative change. Cannon historian Warren Ripley reconciled the terminology as the logical association of “heavy” with “light” when annotating the particulars. I would accept the Ordnance Manual’s nomenclature as definitive, over the pre-war instructions written by Dahlgren, simply because the former outlined the official record keeping standards for inventories.
The Navy added more weapons to the “family” as time passed. Either as an experimental batch or perhaps just a limited production run, a fourth smoothbore bronze piece joined the family in 1853. Often called the 12-pdr “small” boat howitzer, it weighed 300 pounds.
At the onset of the Civil War, the Navy introduced a 12-pdr rifled howitzer based upon the 12-pdr heavy pattern but with a 3.4-inch diameter bore and 12-groove rifling (although some early examples had 3-groove). The rifle weighed 870 pounds, but otherwise worked with the same carriages.
The Navy added another rifle to the system in the middle of the war. Using a similar gun tube pattern to the 24-pdr howitzer, a 4-inch (or 20-pdr) 3-groove rifle weighed 1,350 pounds. But the 4-inch rifle re-introduced trunnions in place of the under-loop (and does not appear to have had a field carriage). Thus the “family” of Dahlgren boat howitzers came to include six types with the particulars as noted in the chart below.
The Dahlgrens compared well to contemporary Army field howitzers:
While the Dahlgren boat howitzers dominated the class, they were by no means the only weapons designed for use on small craft during the Civil War. Norman Wiard provided a batch of steel rifled 3.4-inch boat howitzers for the Army’s North Carolina expedition in 1861. Tredegar produced boat howitzers in both 12- and 24-pdr patterns. And Tredegar also produced an iron rifle, often cited as a Confederate Parrott, but with an underloop for mounting on boats similar to Dahlgren’s system. All certainly worthy of a separate post for later discussion, but one should not confuse these types with the true Dahlgrens.
The Dahlgren boat howitzers, much like the Army’s little mountain howitzer, continued to serve well after the war. Only near the beginning of the 20th century, with the arrival of light breechloading steel rifles and machine guns, were the Dahlgren boat howitzers phased out of service. Anywhere U.S. sailors or marines went ashore, a Dahlgren boat howitzer was not far behind. If the brass cannons could speak, they likely would relate salty tales of landings on southern shores or of far away exotic lands.
Over the next posts on this theme, I’ll look at the ammunition used by the boat howitzers and also discuss the employment of the type.
Aside from on site notes and links provided above, sources consulted for this post were:
Hazlett, James C., Edwin Olmstead, and M. Hume Parks. Field Artillery Weapons of the Civil War, Revised Edition. Urbana and Chicago: University of Illinois Press, 2004.
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.