Shellguns for the spardecks: Dahlgren’s X-inch Shellguns

Back when discussing Rear-Admiral John Dahlgren’s shell guns and their relatives, I used this chart to illustrate the lineage:


The IX-inch shell guns, XI-inch shell guns, and XV-inch turret guns, which saw extensive service, particularly in the waters off Charleston, I’ve given some attention already.  And those guns deserve more attention as time permits.  But today let me look to one of the less common members of the original family of shell guns – the X-inch shell gun.

Prior to Dahlgren’s work, the Navy had in the inventory a limited number of 10-inch shellguns.  These were named 10-inch Shell Gun of 86 hundredweight.  The guns were often cited as Paixhans guns, in reference to the French weapons the Americans used as a model.  West Point Foundry produced thirty-three of these in 1841-2.  Those shell guns were placed in the pivot gun positions  on the spar decks of several pre-war side-wheel steam frigates, namely the USS Mississippi and USS Susquehanna.  But the problem with the gun was it’s limited powder charge and handling weight of the shell.  A four pound charge pushed a 104 pound shell.  The propellant charge was significantly lighter than the British equivalent.  This shell was heavier than contemporary British practice by a factor of almost twenty pounds.  So the American 10-inch “Paixhans” compared unfavorably to similar weapons of the most likely adversary.

When Dahlgren set out to improve the Navy’s ordnance, he put emphasis on placing the largest possible calibers in every position in order to overwhelm any adversary with the sheer weight of fire.  That in mind, Dahlgren wanted to place XI-inch shell guns on the pivots of the new steam sloops being built in the first half of the 1850s.  Even though trials proved the 138-pound XI-inch shells of his design could be handled by gun crews, his superiors were unmoved.  So Dahlgren designed a X-inch gun for those pivot assignments on those new sloops.

Dahlgren’s Memoirs indicate contracts for seven X-inch guns each went to West Point Foundry and Cyrus Alger in December 1854.  West Point produced nineteen in 1855-59.  But records for Alger are a blank.  The only other recorded production run was a batch of 10 from Seyfert, McManus, and Company during the Civil War. Those known production runs are represented on the table below, comparing the particulars of the Dahlgren shell guns:


In service, the X-inch shell guns fired a 103 pound shell, including the filling and sabot.  The table below compares contemporary shells of other calibers:


The service charge authorized for Dahlgren’s X-inch shell guns used a 12.5 pound charge – over three times that of the older shell gun of the same caliber.  The table below is from the 1860 Naval Ordnance Manual:


The heavier charge reflected the improvements made by Dahlgren to gun design, which allowed those heavier pressures in the gun.  During the war, the rating went up to 15 pounds when firing at long range.  The normal charge remained 12.5 pounds, while 10 pounds was recommended for close range (or double shotting).  (See the 1866 version of the service charge table to compare with other guns.)

As for range, the 1866 manual credits the X-inch gun with a 3,000 yard range, at 11° elevation, using the standard 12.5 pound charge.  The larger XI-inch gun could reach only 2,870 yards at the same elevation.  And the IX-inch gun only 2,788 yards at 11°.  So the X-inch gun seemed to have had an advantage in range over the others in the family.  However, the largest gun of the three types had a shell with a six pound bursting charge (and the kinetic energy of 130 pounds of iron).  The X-inch offered only a four pound bursting charge inside 97 pounds of iron.   Perhaps the destructive potential of those larger shells was of greater advantage than range.

The original ships receiving the X-inch guns were the USS Merrimack, USS Wabash, USS Minnesota, USS Roanoke, and USS Colorado.  Two of those ships, of course, were later converted to ironclads – one for each side, mind you.  The two X-inch guns from the Merrimack may have been the “two 10-inch columbiads” reported captured when Virginia seized the Gosport Navy Yard on April 21, 1861. The USS Brooklyn received two X-inch shell guns and USS Pocahontas received a single gun.

Since I’ve been on a Charleston swing of late, let me mention the service of those ships in those waters.  The Brooklyn and the Pocahontas were involved with the early war operations there, but moved to other stations after the first year of the war. The Wabash served in the South Atlantic Blockading Squadron through the summer of 1863 and fired her share of shells at the Confederate forts.

The X-inch Guns conformed to Dahlgren’s design standards to include the cylindrical reinforce and sweeping curves.  The guns were cast solid, with excess metal around the chase to improve overall strength of casting.  The excess was trimmed off and the guns bored out in the traditional manner at the foundry.  Normally, at this point in a “cannon” post, I start the walk around photos.  Can’t do that here.  Of the twenty-nine known produced not a single X-inch Dahlgren is known to survive.  But there is a photo of one serving on the Wabash during the war.

The crew steals the show here.  Particularly that fabulous beard on the right.  The caption indicates this was the aft pivot gun on the Wabash.

The X-inch Dahlgren shell guns also saw service on the Mississippi River gunboats.  But the more widely produced IX-inch and XI-inch guns far outnumbered the X-inch guns in any theater.

Published by Craig Swain

"Historical marker hunter" and Civil War enthusiast.

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