Introduction to the American 42-pdr Seacoast Gun

Last month while discussing the artillery captured by the South Carolina forces upon the state’s secession, I mentioned quantities of 42-pdr seacoast guns.  From the end of the War of 1812 until the Civil War, the US Army purchased over 500 weapons in the 42-pdr seacoast classification.  Based on contract specifications, those appeared in four different model numbers:

  • 42-pdr Model 1831 of similar outline to smaller, contemporary seacoast guns – featured a breech ring on the knob, single reinforce, and a cavetto on the muzzle moldings.
  • 42-pdr Model 1839 which added two inches length to the reinforce and dispensed with the ring over the knob.
  • 42-pdr Model 1840 adding a cylindrical first reinforce of half the overall reinforce length (thus having two reinforces).  Also simplified muzzle molding, but adding a chase ring.
  • 42-pdr Model 1845 differing little from the earlier model, but machine all over for a smooth appearance.

In accordance with the “pounder” designation system, all the 42-pdrs had a 7-inch diameter bore.  However the early models had slightly more windage, with the bore about a tenth of an inch wider.  The table below summarizes the important dimensional variations (and provides some production figures I’ll cite later).

As noted above, the most important evolution through the model numbers was the reinforce configuration.  The cylindrical first reinforce used on Models 1840 and 1845 reflected new understanding of the physics involved with gun design.   Although the slight reduction in weight was of little consequence for coast defense use.

The 42-pdrs shared common barbette and casemate carriages with the 8-inch Columbiads.  However, the 8-inch diameter trunnions and 25-inch rimbase spacing required some modifications for the larger caliber weapon.

The Army manuals do not indicate any performance differences between the models, listing only a “generic” 42-pdr on barbette carriage for range tables.   From the 1862 Ordnance Instructions the table below notes the powder charge at 10.5 pounds, with ranges in yards indicated for each degree of elevation.  (However in a different table, the same set of instructions indicates the standard service charge was 9 pounds.)

The 42-pdrs fired shot, shell, case, grapeshot, canister, and carcass.  Diameter of regulation shot and shell was 6.84 inches, offering only slight windage off the bore.  Solid shot weighed 42.7 pounds.  Shells weighed only 31 pounds empty.  Filled, the shell contained 1.5 pounds of powder.

Artillerists had the option to fire solid shot as “hot shot” in order to start fires on wooden ships.  Furnaces, found at nearly all seacoast fortifications, heated the shot until white hot.  Gunners used specially packed reduced charges along with a clay or wet hay wadding to prevent the hot projectile from igniting the powder prematurely.  If fired properly, the solid shot lodged into the ship’s wood hull and could then start a fire.  When heated to the desired temperature, a 42-pdr solid shot expanded by about a tenth of an inch, making it very close on windage.  Tests with shot (by Lieutenant Thomas J. Rodman) before the war demonstrated that heating and cooling cycles change the shot diameter by about 0.05-inch (or half that of the heated expansion).  Such implied a limit to the number of times one could prepare a hot shot.

Case shot, with thinner walls, weighed just over 20 pounds empty.  When loaded, the case shot contained 306 lead musket balls and a nine-ounce bursting charge.  Fully prepared the case shot weighed 39 pounds.

Grape shot consisted of nine cast iron balls in a loose stand sandwiched between base plates with hoops and a central retaining rod.  A stand of 42-pdr grape used nine balls of 3.15-inch diameter weighing 4.2 pounds each.  While effective as an anti-personnel projectile, the intended use of grape was against the rigging of ships, and thus of declining value as steam propulsion appeared.

The preferred anti-personnel round by the time of the Civil War was canister.  A canister round for the 42-pdr consisted of a “can” filled with twenty-seven 2.25-inch diameter, 1.5-pound projectiles packed with sawdust.  Filled, the canister weighed 48 pounds.

Carcass, was a throw back to the use of incendiary projectiles from medieval times.  The carcass was cast as shells with three additional holes.  Filled with flammable material, such as pitch or portfire, the substance ignited upon firing of the propellant charge.  This arrangement was dangerous compared to hot shot, and fell into disuse.  Although to my knowledge none were used in the Civil War, the carcass remained on the books.

Other projectiles often mentioned for the 42-pdrs include chain-shot, bar-shot, and double shot.  The first two were obsolete by the time of the Civil War, intended to destroy ship’s rigging.  The later term could mean either double loading of solid shot or use of a special projectile for proofing.  During tests at Fort Monroe before the war used elongated “double shot” projectiles for proofing.

In spite of this very lethal array of projectiles, at the start of the Civil War the Army felt the 42-pdr class too small for seacoast operations in light of technical advances.  But the outbreak of war ensured the guns in service would remain in forts, defending positions for both Federal and Confederate.

Ft Sumter 3 May 2010 308
42-pdr Seacoast Gun Model 1845 at Fort Sumter

Guns, such as the one pictured above at Fort Sumter today, remained in the inventory but were reclassified as “Garrison Guns” to indicate the the downgrade and obsolescence.

In follow-up posts, I’ll look more at the service history of the 42-pdr guns and provide photos of some survivors.  But for starters, I’d invite readers to look back at a post made in January last year detailing the Model 1831.


Aside from on site notes and links provided above, sources consulted for this post were:

Ordnance Manual for Use of the Officers of the United States Army.  Philadelphia: J.B. Lippincott, 1862. (Google Books copy)

Bell, Jack. Civil War Heavy Explosive Ordnance:  A Guide to Large Artillery, Projectiles, Torpedoes, and Mines. Denton, Texas:  University of North Texas Press, 2003.

Birkhimer, William, Historical Sketch of the Organization, Administration, Material and Tactics of the Artillery, United States Army.  Washington:  James J. Chapman, 1884.  Particularly pages 275-9 discussing the evolution of the American systems of artillery.

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.


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