Note:  Do not rely on this information. It is very old.

Gun Metal

Gun Metal, an alloy consisting of copper and tin. For smaller cannon its composition is about copper 90.5, tin 9.5; for larger guns the quantity of tin is slightly increased. It possesses in a high degree the qualities necessary for the purposes to which it is applied - viz. hardness, great tenacity, and the capability of being cast without difficulty. It is usually prepared by fusing copper, tin, and bronze with old gun metal, the two former being first fused together and added to the fused bronze and old metal. The alloy formed is kept melted for about half-an-hour and then cast in the moulds employed.