Definition of "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.

1693 May, Thomas Povey, “I. The Method, Manner and Order of the Transmutation of Copper into Brass, &c. By Thomas Povey, Esq; Brought into the Royal Society, of which He is a Fellow.”, in Philosophical Transactions, number 200, [London]: Printed for S[amuel] Smith and B[enjamin] Walford, printers to the Royal Society, at the Princes Arms in St. Paul's Church-yard, page 736

Braſs, Copper, Latten, Bell-Metal, Pan-Metal, Gun-Metal, or Shruff-Metal, whether clean or mixed, carried beyond Sea, forfeits double the Value thereof; (Tin and Lead only excepted) the Informer half, […]

1702, “An Abridgment of Several Statutes Now in Force and Use, Relating to Her Majesty’s Customs, which were Made before the Act of Tonnage and Poundage, 12 Car. II [marginal note: Braſs, Copper, &c. Prohibited to be Exported]”, in The Act of Tonnage & Poundage, and Rates of Merchandize, with the Further Subsidy; the Old Import; the Additional Impost; and All Other Duties Relating to Her Majesties Customs, Now Payable upon Any Sort of Merchandize Imported or Exported. [...], London: Printed by Charles Bill, and the Executrix of Thomas Newcomb, deceas'd; printers to the Queens Most Excellent Majesty, pages 701–702

Phosphorus is known to improve the strength of copper, and to make it cast soundly. Abel, chemist to the British War Department, stated before the Institute of Civil Engineers, that he had made some experiments upon the combinations of phosphorus and copper, and "had found that by the introduction of a small proportion, say from 2 to 4 per cent., of phosphorus into copper, a metal was produced remarkable for its density and tenacity, and superior in every respect to ordinary gun-metal. […] The experiments alluded to were merely preliminary, and had been, to a certain extent, checked by the improvements since introduced in the construction of field-guns, which had led to a discontinuance of the employment of gun-metal."

1874, “ARTILLERY”, in [Oliver] Byrne, [Edward] Spon, editors, Spons’ Dictionary of Engineering, Civil, Mechanical, Military, and Naval; with Technical Terms in French, German, Italian, and Spanish, volume I, London: E[rnest] & F[rancis] N. Spon, 48, Charing Cross; New York, 446, Broome Street, page 177

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.

1896, William T. King, “John A. Ives & Brother – 1864”, in History of the American Steam Fire-engine, [Boston, Mass.]: [Pinkham Press]; reprinted Mineola, N.Y.: Dover Publications, 2001, page 92

It is three tiers high inside the prison and everything is the color of gunmetal. Everything is dark and cold, except for those patches of light, where authority stands.

1956, James Baldwin, chapter 3, in Giovanni’s Room, New York, N.Y.: Dial Press, page 149; reprinted New York, N.Y.: Dell, 1988

Gunmetals are alloys of copper, tin and zinc, formerly used for casting cannon. With lead additions they become suitable as bearing materials and are called leaded gunmetals (the US term is leaded red brass); they are quite often misnamed bronzes.

1984, D[onald] A. Wight, “Materials”, in C[hristopher] T. Wilbur and D. A. Wight, Pounder’s Marine Diesel Engines, 6th edition, London: Butterworths, reprinted 1986, page 593

Of his addictive behavior, he [Robert Downey Jr.] told a judge, "It's like I have a shotgun in my mouth, and I've got my finger on the trigger, and I like the taste of the gunmetal."

2015, Dan Casey, “Robert Downey Jr.”, in 100 Things Avengers Fans should Know & Do before They Die, Chicago, Ill.: Triumph Books, page 95

Yet even asleep, a Sabre, Jaguar, Harrier, Phantom, Falcon or Eagle holds the eye as a design classic, and that worrisome beauty is still there close up—the cared for, nurtured, spoiled feel, the expensive finish, the quality of the materials, the craftsmanship evident in the flush rivets, the highly polished canopy, the gunmetal sheen of the external instrument sensors, each carefully protected by rubber sheaths with flapping red tags to remind the pilot to take them off before flight.

1999, Ivan Rendall, “Preface”, in Rolling Thunder: Jet Combat from World War II to the Gulf War, 1st American edition, New York, N.Y.: The Free Press, page ix