Gun metal, also known as red brass in the United States, is a type of bronze – an alloy of copper, tin, and zinc. Proportions vary but 88% copper, 8–10% tin, and 2–4% zinc is an approximation. Originally used chiefly for making guns, it has largely been replaced by steel for that purpose. Gunmetal casts and machines well, and is resistant to corrosion from steam and salt water. It is used to make steam and hydraulic castings, valves, gears, statues, and various small objects, such as buttons. It has a tensile strength of 221 MPa to 310 MPa, a specific gravity of 8.7, a Brinell hardness of 65 to 74, and a melting point of around 1,000 degrees Celsius.

Variants

Gunmetal can also mean steel treated to simulate gunmetal bronze. Bushings made of this metal are used in machinery.

Other uses of gun metal

Gun money, Irish late 17th-century emergency coins, contain gunmetal, as worn and scrapped guns were used to make them; but also many other metals, in particular brass and bronze, as people donated pots and pans and other metal objects. External doors and windows of offshore rock lighthouses are often made of gunmetal due to its corrosion resistant properties.