Dahlgren 12-pdr Heavy Boat Howitzer

Of the family of Dahlgren Boat howitzers, the most numerous among survivors are the 12-pdr heavy type.  (Although the most widely produced was the 24-pdr heavy.)  Originally labeled as “medium” by Admiral John Dahlgren, Navy instructions re-designated the type, likely for a logical naming convention (compared to the “light” howitzers of smaller size).   For particulars and comparison to others in the family, reference the table below, with the “heavy” listed on the second column:

Dahlgren Boat Howitzer "Family"

As mentioned in the earlier posts, the 12-pdr heavy was intended to arm launches from frigates and smaller boats from the Ships-of-the-Line.   However, advances in technology rendered the old ship type classification obsolete by the Civil War.  The Navy, needing weapons to arm various impressed blockaders,  issued 12-pdr heavy howitzers to ships of all sizes during the war.

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12-pdr Heavy Boat Howitzer, Reg. #45, Fairfax CH, Va.

Unable to keep up with demand with the facilities at the Washington Navy Yard’s gun shop, the Navy contracted both Ames Manufacturing and Cyrus Alter & Company, both of Massachusetts, for additional production.  From 1849 until 1865, the Washington Navy Yard produced 197 12-pdr heavy howitzers.  Ames added 202 more between 1863 and 1865.  Alger provided 57 in 1863-64.  Based on one cataloged survivor, Alger produced boat howitzers for other customers besides the Navy.  Thus, while Navy contract deliveries totaled 456, there may be a few more examples in the count produced on other contracts.

The 12-pdr heavy followed the common lines used for all the Dahlgren boat howitzers.  The exterior was rather plain, with no rings or adornments.  The lack of trunnions gave the boat howitzer a streamlined appearance.   A loop under the barrel allowed a pin to attach the howitzer to a carriage.  Below is a view of the loop on the US Navy Yard registry number 45, currently on display outside Fairfax Courthouse, Virginia.

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Close-up of Attachment Loop

Also seen in this view are the bolts used to connect components of the iron carriage used for landing parties.

The breech was hemispherical in profile.  The knob, supported by a modest neck, was pierced for an elevation screw.  The screw itself pivoted upon a block attacked to the trail of the field carriage.

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Breech, Knob, and Elevating Screw

The sight slid into a hole on the top of the breech, and was fixed in place with a screw through the back.

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Top of Breech - Sight Bracket, Lock-piece Arm, Vent and Markings

On the right side of the breech was an arm or fixture which supported the lock-piece.  The lock-piece, missing from this example, was spring-loaded and tripped by a catch.  The hammer of the lock-piece fell upon a primer placed in the vent.   A blade sight on the top of the muzzle matched the center sight line.

Notice between the vent and the sight bracket are the markings “U.S.N.Y. Washington 757 lbs  58 pre.  // No. 45.”  This indicates the heavy was produced at the Washington Navy Yard, weighed 757 pounds and had a 58 pound preponderance.  The howitzer was given the registry number 45.  Other markings appear further up the barrel.

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Markings over the Middle of Howitzer

Below a fouled anchor are the marks “12-pdr // Boat Howitzer // 1856 // J.A.D. ”  This particular piece was accepted into service in 1856 after inspection by John A. Dahlgren himself.

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Bore of Boat Howitzer

Debris in the bore of the howitzer prevents a clear view of the gomer chamber.

The other Dahlgren boat howitzer at Fairfax Courthouse is similar in profile, but with some differences which raise a question or two.

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Left Hand Side Sight and Lock-piece Arm

Apparent, just by a quick view of the breech, this second example has the lock-piece arm on the right, and a “lug” with a hole for the sight.  And further up the barrel, on the left side above the loop is another lug for mounting the front sight.

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Lug for Front Sight

Unfortunately, no markings are visible on this second piece.  From a purely tactical point of view, moving the sight to the left side of the weapon does make sense.  Consider the gunner firing the howitzer at a high elevation, which one is apt to do with a howitzer.  At some angles, the gunner’s view of the target would be obscured by the muzzle of the howitzer.  The same “off center-line” arrangement was made on Parrott rifles and other Civil War era weapons.

Without markings, it is impossible to tell if this was a modification used in early or late production, or a manufacturing variation.  Indeed, the absence of marks may indicate this piece was produced outside of the Navy contracts, which may mean the sight line variation was a special customer requirement.

Since both weapons in Fairfax are mounted on authentic (or at least authentic looking!) carriages, these are also worth examination.

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Side View of Unmarked Howitzer, and Carriage Details

Already mentioned above, heavy bolts join the trailing leg and axle tree.  A bar running from the axle line down to the trail (on the left of this view) provides additional support for the carriage frame.  A bronze rack, with pins, lays across the tree and trailing leg.   While not noted in Dahlgren’s instructions, this fixture corresponds frames for carrying ammunition boxes seen on contemporary photographs.

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Unmarked Dahlgren at Fairfax

Pins at the end of the axle fixed the hub of wrought iron wheels.  The wheels had twelve spokes.  Rather straightforward design.

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Trailing Leg Wheel

The trailing leg had a smaller third wheel.  The wheel sat in a bracket.  A socket at the end of the bracket supported the drag rope.   Notice the mounting inside the bracket for the wheel.  This allowed the wheel to pivot up when the piece was deployed for action.

In concluding this “up close” look at the Dahlgren 12-pdr Heavy Boat Howitzer, consider the very straightforward design of both the howitzer and carriage.  This weapon was intended for use by naval landing parties going into harm’s way, and likely to be outnumbered from the start.  Sure, these are wrought iron and bronze, but even today the old cannon convey a sense of dependability and utility.

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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.

Published by Craig Swain

"Historical marker hunter" and Civil War enthusiast.

6 thoughts on “Dahlgren 12-pdr Heavy Boat Howitzer

    1. Well, the carriages are wrought iron. Weighed about 500 pounds each.

      Regarding recoil, Dahlgren said it was slight. In his 1848 test, the “heavy” howitzer (which he termed at the time a medium) recoiled between 18 to 29 inches during the firing of 20 rounds on the ship carriage. Based on that test, Dahlgren was able to dispense with breeching tackle for the howitzers. I don’t recall if he posted results of firing from the land carriage. But I can’t see it being a serious issue.

      BTW, I’ve linked your blog in the blogroll. Thanks for commenting!

  1. Sir: So you know. There is another examle of the side mounted sights on the “Heavy “at the museum in Seattle WA, Cost Guard Station. Of note is the absence of the the vent liner in that gun but the front sight blade is cast as part of the “lug” you see on the gun your have posted. YOS, Boat’s, USS Tahoma, WCWA, TSP, TTSP-LLC

  2. Craig, you wrote: “The lock-piece, missing from this example, was spring-loaded and tripped by a catch. ” The bronze hammer has a circular groove at the rear. The lanyard wrapped around that sector and when pulled, caused the hammer’s head to rotate toward the vent and strike it. I put detailed photos of a Dahlgren hammer and original lanyard in a posting on the Company of Military Historians Forum some time back.

    1. I’ve seen the article you posted. My question would be about the actual terminology used. Dahlgren referenced “lockpiece” in the original notes, then in later years a “hammer.” Which do you feel is correct?

  3. Seattle-US Coast Guard Station (gone 2009)
    2 12-Pound US Navy Bronze Heavy Dahlgren Boat Howitzers,
    on wrought iron field carriages
    Ames Mfg. Co. REG #245, 768 lbs., 1863
    Ames Mfg. Co. REG #246, 772 lbs., 1863
    These two howitzers were placed on display a Seattle’s Woodland Park January 23, 1914. Major (later general) Mark W. Clark requested the loan of these guns in 1939. Both were moved to the Coast Guard museum in 1976. They were used by the Harriet Land Landing Party to reenact a Civil War landing party. In 2003 #245 was sent to the US Coast Guard’s Integrated Support Command in Portsmouth, VA. Gun #246 was transferred to the US Coast Guard Training Center Weapons School at Yorktown, VA in September 2009.

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