gunmetal

The beſt Guns are not made of malleable Metal, and cannot be made of pure Copper or Braß; but it is neceſſary to put in courſer Metals to make it run cloſer and ſounder, as Lead and Pot-metal. […] About 20l. of Lead is uſually put into 100l. of Pot-metal; but about 6l. is ſufficient to put into 100l. of Gun-metal.

The pump [of the steam fire-engine], being at the forward end, was made of gun metal and was double acting, having eight brass suction-valves, four on each side, and four discharge valves, opening into the air vessels, to which a double discharge valve, having one opening on the inside and two on the outside, was attached for the purpose of using two lines of hose.

gunmetal: