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The Armstrong 100-ton gun is the largest muzzle-loading artillery piece in English history. Made by the ordnance division of Armstrong Whitworth, a British manufacturing firm, the 17.7-inch gun is also considered to be the first fully automated cannon. Armstrong Whitworth offered the gun to the Royal Navy in 1870, but the navy deemed it too costly and too heavy to be effective in combat. Four years later the company agreed to supply the Italian navy with eight of the guns for service on the sister battleships Duilio and Dandolo. The Royal Navy, alarmed at the possibility that the Italian battleships could outgun its own ships and threaten its key Mediterranean outposts of Gibraltar and Malta, ordered four of the same guns as coastal armaments.

Each gun and its mount weighed 150 tons—100 imperial tons—and offered awe-inspiring firepower, with its 2,000-pound shells propelled by a full charge of 450 pounds of black powder. The shells came in armor-piercing, high-explosive, and shrapnel varieties, with the AP and HE munitions having an effective range of five miles and a maximum (but largely ineffective) range of eight miles. The gun’s steam-powered hydraulic system automated the swabbing out, loading, and ramming procedure, allowing its 35-man crew to fire a shell every six minutes.

As it turned out, however, none of the 100-ton guns was ever fired at an enemy. Though they stayed in service until 1906, these epic artillery pieces had been rendered obsolete years earlier by breechloading weapons that used new high-pressure, smokeless propellants. The Armstrong guns were also prohibitively expensive—firing a single shell cost as much as the combined daily pay of 2,400 infantrymen. Today only two specimen survive, at the Rinella Battery in Kalkara, Malta, and Napier of Magdala Battery, on Rosia Bay, Gibraltar. MHQ

Chris McNab is a military historian based in the United Kingdom. His most recent book is The Falklands War Operations Manual (Haynes Publishing, 2018).


This article appears in the Summer 2019 issue (Vol. 31, No. 4) of MHQ—The Quarterly Journal of Military History with the headline: Weapons Check | Armstrong”100-ton gun” 

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