Reported in Scientific American, this Week in World War I: December 4, 1915

The belligerant nations in World War I strained their manufacturing capacity to the utmost to provide the most effective weapons and ammunition for their vast armed forces. At the leading edge of technology was the design and manufacture of large-caliber guns designed for use on the newest “dreadnought” battleships or as siege artillery on land.

An article from one hundred years ago, “The Manufacture of English 12-Inch Guns,” by Carl F. Jeansen, an ordnance engineer at the Washington Navy Yard, described the process of building large wire-wound guns. As with any major engineering project, the goal was to balance massive strength with useful lightness while keeping to close tolerances. The gun had to withstand the high heat and internal pressure of the exploding propellant, multiple times, but it also needed to be portable enough to allow it to be mounted on a ship or some variety of gun carriage on land. Accuracy of manufacture enabled the trajectory of each shell fired to be calculated and replicated as precisely as possible.

Four cutting tools shape the outside of a 12-inch gun.
Image: Scientific American, December 4, 1915

These guns were built up of multiple layers, the outer layers compressing the inner layers. It was thought that the life of the gun was lengthened by this composite arrangement. The gun had an inner tube or liner, an outer tube, then several layers of immensely strong square-sectioned wire that was tightly wound around these tubes, an outer jacket, and then various hoops and projections to hold the gun in its carriage. Rifling was cut into the barrel and a breech block was added to seal the end and allow it to be loaded. “a variation of one one-thousandth of an inch (plus or minus 0.001” ) is allowed in turning the  surfaces.”

Manufacture of wire-wound U.S. 14-inch naval gun, showing the composite construction: several layers of square-sectioned wire are tightly wound onto the outside of the gun tube. 
Image: Scientific American Supplement, May 22, 1915

Every step was painstakingly tracked and assessed: “All the processes of manufacturing the forgings are closely inspected and test specimens are cut from the forgings and pulled apart in testing machines. Records are kept of the elastic limit, tensile strength, elongation and contraction of area, etc. If the test specimens do not come up to specifications the forging is rejected. Chemical and microscopic examinations of the steel are also made.” Even so, the physical stresses of firing the gun meant that “When a 12-inch gun has been fired 100 to 225 shots it does not shoot accurately and has to be replaced.” The gun could be sent back to the factory and the lining tube replaced.

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Our full archive of the war, called Scientific American Chronicles: World War I, has many articles from 1914–1918 on innovations during the First World War. It is available for purchase at www.scientificamerican.com/products/world-war-i/