Heavy Iron to Protect the Coasts: 15-inch Rodman Guns

I’ve discussed the prototype 15-inch Rodman as the culmination of Thomas J. Rodman’s many experiments. While production figures paled in comparison to the 10-inch version, the number of 15-inch guns exceeded that of the 8-inch Rodmans. To the very last years of the 19th century, the 15-inch Rodman remained a component of America’s coastal defenses. These guns were the “big iron” of the forts protecting the coastline.

As mentioned in the previous posts, the production guns differed from the lone prototype. The modified production design moved the trunnions 1 ¼ to the rear, eliminating the preponderance at the breech. The breech featured the sockets for the new elevating system. The 15-inch guns averaged around 50,000 pounds. Overall length was 190 inches. The gun gradually tapered from its 48 inch maximum diameter over the seat of the charge down to 25 inches at the muzzle. The trunnions were 4.5 inches long and 15 inches in diameter.

Like the other calibers, the first production batches of 15-inch Rodmans came from Fort Pitt Foundry. The Pittsburgh vendor delivered the first two production guns in the summer of 1862.* These were registry numbers 2 and 3, continuing the same sequence as the prototype gun. Fort Pitt continued deliveries in single digit batches through November 1866. However the foundry delivered eleven more in August 1871. These were likely cast in 1866 and only accepted by the government five years later. Overall, Fort Pitt sold 145 of the 15-inch guns to the Army.

Baltimore 16 May 10 283
15-inch Rodman Guns - Fort Pitt #36 and #42 at Fort McHenry

Aside from these two pictured at Fort McHenry, five more Fort Pitt 15-inch guns survive today.

Cyrus Alger & Company received a contract to produce 15-inch Rodmans in 1862. However the Boston company didn’t deliver the first until October 1863. Production continued through June 1866 with 142 delivered. Like Fort Pitt, Cyrus Alger delivered another eleven guns in November 1871 (again, probably produced in 1866 and delivered later).

Thirteen of Alger’s 15-inch guns survive today. Previous posts introduced two Alger 15-inch guns at Fort Foote, Maryland. These well maintained guns provide excellent subjects for walk-around. The older of the set is Alger registry number 1 (yes the company’s first) on a center pintle barbette carriage.

Fort Trip 26 Mar 11 141
15-inch Rodman - Alger #1

In compliance with regulation standards, the important markings appear on the muzzle. In this case, registry number 1, inspected by Thomas J. Rodman himself, weighted 49,392 pounds when inspected in 1863. The manufacturer’s stamp at the top has eroded.

Fort Trip 26 Mar 11 121
Muzzle of Alger #1

Looking back down the gun, the trunnions appear as just small cylinders attached to the massive barrel.

Fort Trip 26 Mar 11 145
Trunnions of Alger #1

The breech conforms with the Rodman design, featuring the “mushroom” knob. Notice what appears to be a proofing line around the wider part of the breech.

Fort Trip 26 Mar 11 146
Breech Profile of Alger #1

The breech face has eleven squared sockets. Other 15-inch guns, notably the guns seen above at Fort McHenry have thirteen.

Fort Trip 26 Mar 11 139
Breech Face of Alger #1

Looking down the barrel, the lump on the top is a sight base. Clearly with the proportions of the 15-inch Rodman a muzzle sight was impractical.

Fort Trip 26 Mar 11 134
Looking down barrel of Alger #1

I’ve seen some wartime photos that appear to show trunnion mounted sights. This would seem more practical and match similar practices with heavy Parrott rifles. However keep in mind the employment scenarios for these heavy guns. Rodmans long occupied positions in coastal forts. Battery officers had decades (yes decades) to measure ranges and establish detailed firing tables and what we might call “range cards.” With such records, “iron sights” were likely just used for conformation of the elevation and traverse.

The bore of the 15-inch gun is… cavernous.

Fort Trip 26 Mar 11 132
Bore of Alger #1

The battery mate at Fort Foote is Alger registry number 30, produced in 1864. It sits upon a front pintle barbette carriage.

Fort Trip 26 Mar 11 100
15-inch Rodman - Alger #30

The foundry numbers on most Rodman guns, placed on the rimbase, has eroded away with time. However the number “1614” is still legible on this Rodman.

Fort Trip 26 Mar 11 115
Foundry Number over Trunnion

The third vendor to produce 15-inch Rodmans was Seyfert, McManus, & Company of Reading, Pennsylvania at the Scott Foundry. That vendor received orders in the fall of 1863. After its first delivery in May 1864, the company produced a total of 24 guns. Similar to Fort Pitt and Alger, the foundry received credit for four additional guns in 1871. Two of those are at Fort Sumter today.

Ft Sumter 3 May 2010 169
15-inch Rodman - Seyfert, McManus #22

The other two are across the bay at Fort Moultrie. All four guns have date stamps of 1866 or 1867, leaving the conclusion that the foundry produced the guns some five years before the Army paid for them. Notice the breech face of the gun – eleven rounded sockets.

Ft Sumter 3 May 2010 168
Breech of Syfert, McManus #22

The four guns in the Charleston area, much like 15-inch Rodmans at other locations, remained in the seacoast forts right up until 1900. The presence of these guns as seacoast armament bends the normal application of the adjectives “obsolete” and “obsolescent.” The 15-inch Rodmans served the nation’s defense well into obsolescence and well after the guns were obsolete!

At some point in the future I plan several posts on the post-war use of the Rodman guns.  From a weapons development standpoint, what’s interesting is the desire to “pinch a penny” with rifle and breechloading modifications, some just considered and others applied.  Although these guns never fired a shot in anger, I imagine they have a few stories to tell.


* Production details for the 15-inch Rodman Guns are from Edwin Olmstead, Wayne E. Stark, and Spencer C. Tucker, The Big Guns: Civil War Siege, Seacoast and Naval Cannon (Alexandria Bay, NY: Museum Restoration Service, 1997), Appendix C166, pages 262-265.

Published by Craig Swain

"Historical marker hunter" and Civil War enthusiast.

4 thoughts on “Heavy Iron to Protect the Coasts: 15-inch Rodman Guns

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: