Converted Rodman Rifles: Defending the coast in the time of lean budgets

Earlier this week, Keith Harris asked for a quick cannon identification via Twitter. Feel free to click over to Keith’s picture, but the gun below from Fort McHenry, Maryland is similar.

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8-inch Rifle Converted from a 10-inch Rodman at Fort McHenry

The exterior shape of this gun should look familiar. It’s a 10-inch Rodman. But a close look at the bore reveals something decidedly non-standard for that type of gun. This was a post-war modification to the gun. The story is interesting not only because it involves a Civil War cannon, but also because it carries forward all the way to the 20th century.

During and shortly after the Civil War the Army felt the Rodmans were sufficient to defend the coastlines. The combatants in the war deployed the most advanced warships of the day, and the Rodman guns rated well enough to deal with that threat. However within a decade, developments in Europe eclipsed the Civil War era weapons. Ship builders turned to steel, over the wood and wrought iron of the Civil War. So the coastline defenses needed improved guns.

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Pair of Converted 8-inch Rifles at Fort McHenry

Trouble was the U.S. had a lot of coastline to defend, but not a whole lot of money to spend on guns. Given the limited budget for updates, the Army looked around for options… and saw hundreds of Rodman smoothbores.

Recall that during the Civil War many of the old 32-pdr and 42-pdr guns got a new lease on life as “rifled guns.” With that experience in mind, soon ordnance officers and weapon developers stepped forward with different schemes to rifle those Rodmans. I’ve seen well over a dozen different plans for rifling Rodman guns, including plans for 15-inch conversions to 12-inch rifles. Some even provided for breech loading conversion.

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Muzzle showing breech insertion

The most successful (and I use that qualifier in relative terms) conversions involved the 10-inch Rodman guns. At least four different groups of Rodmans in that caliber underwent conversion to 8-inch rifles. Those four conversion plans required the original gun to be reamed out to fit new bore sleeve, and often a liner, by way of insertion. The sleeve and liner were usually steel, but some early experiments used wrought iron. The groups differed in the technique used for inserting the sleeve (through the muzzle or through the breech) and the number of rifle grooves.

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8-inch Converted Rifle on blocks at Fort McHenry

All told the Army contracted for conversion of over 200 of the 10-inch Rodmans from about 1876 to 1890. After successful tests at Sandy Point, New York, the guns went to the forts as the primary anti-ship weapon in the arsenal. However even at that time, everyone recognized the conversions were obsolete given the armament of European navies. But that was all the Army could acquire given the limited peacetime budgets.

These weapons remained in the Army’s inventory to the end of the century. The 1891 Manual of Heavy Artillery Service provided a range table and a dozen pages of drill instructions.

So 4700 yards range for a 35 pound powder charge. Still not all that impressive compared to contemporary breech-loading, steel rifles. For instance the “new” M1888 8-inch breechloading gun on a disappearing carriage rated over 10,000 yards. But of course the Army didn’t receive many of those “new” guns until the late 1890s.

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8-inch Rifle showing breech insertion plug

These converted rifles remained in the forts even during the Spanish-American War. And a good number of them survive today (as seen in the photos supporting this post). The service history of these guns spans four decades. Heck, these guns rival the B-52 bomber in terms of service life!

The gun Keith photographed is located in the Grand Army of the Republic plot of the Rosedale Cemetery in Los Angeles. I’m sure Keith will have a story to tell about that aspect of the gun’s history on his blog. To me, it looks like a gun which needs some tender loving care… and a few coats of paint.