Gunmetal is a variety of bronze and formerly used for making ordnance (guns).
Modern admiralty gunmetal is composed of 88 percent copper, 10 percent tin, and 2 percen zinc and is used for gears and bearings that are to be subjected to heavy loads and low speeds. It withstands atmospheric, steam, and seawater corrosion and is suitable for valves, pump parts, and steam fittings.