In the late 1800s, a legal battle erupted between two ammunition giants, the Union Metallic Cartridge Company and the United States Cartridge Company, over the technology used to manufacture cartridge shells. The case, which wound its way up to the U.S. Supreme Court, offers a revealing glimpse into the early American patent system and the fierce competition in the rapidly industrializing arms industry.

At the heart of the dispute was a patent granted to Ethan Allen in 1860 (reissued in 1865) for a machine that could form the hollow rim of a cartridge shell in a single stroke, a significant improvement over prior methods that required multiple spinning operations. The Union Metallic Cartridge Company, having acquired rights to Allen’s patent, sued the United States Cartridge Company for infringement.

These cartridges, with their distinctive recessed rims, were the key product Allen’s machine was designed to produce efficiently. Forming this critical feature in one step was a major breakthrough.