thumb|A stick of cordite from World War II
thumb|A sectioned British 18-pounder field gun shrapnel round, World War I, with bound string to simulate the appearance of the original cordite propellant
thumb|Close-up of cordite filaments in a [[.303 British rifle cartridge (manufactured in 1964)]]
thumb|Burning a strand of cordite from a [[.303 British round]]
Cordite is a family of smokeless propellants developed and produced in Britain since 1889 to replace black powder as a military firearm propellant. Cordite is made by combining two chemical high explosives: nitrocellulose and nitroglycerine in certain ways, and is therefore a chemical high explosive moderated with another chemical high explosive. They are designed, in normal use, to produce a subsonic deflagration wave rather than the supersonic detonation wave produced by brisants, or high explosives. The hot gases produced by burning gunpowder or cordite generate sufficient pressure to propel a bullet or shell to its target, but not so quickly as to routinely destroy the barrel of the gun.
Cordite was used initially in the .303 British, Mark I and II, standard rifle cartridge between 1891 and 1915. Shortages of cordite in World War I led to the creation of the HM Factory, Gretna on the English–Scottish border, which produced around 800 tons of cordite per week. The UK also imported some United States–developed smokeless powders for use in rifle cartridges. Cordite was also used for large weapons, such as tank guns, artillery, and naval guns. It has been used mainly for this purpose since the late 19th century by the UK and British Commonwealth countries. Its use was further developed before World War II, and as Unrotated Projectiles for launching anti-aircraft weapons. Small cordite rocket charges were also developed for ejector seats made by the Martin-Baker Company. Cordite was also used in the detonation system of the Little Boy atomic bomb dropped over Hiroshima in August 1945.
During World War II, double-base propellants were very widely used, and there was some use of triple-base propellants by artillery. Triple-base propellants were used in post-war ammunition designs and remain in production for UK weapons; most double-base propellants left service as World War II stocks were expended after the war. For small arms it has been replaced by other propellants, such as the Improved Military Rifle (IMR) line of extruded powder or the WC844 ball propellant currently in use in the 5.56×45mm NATO. Production ceased in the United Kingdom around the end of the 20th century, with the closure of the last of the World War II cordite factories, ROF Bishopton. Triple-base propellant for UK service (for example, the 105 mm L118 Light Gun) is now manufactured in Germany.
Adoption of smokeless powders by the British government
Gunpowder (black powder)
Gunpowder, a combustable mixture of sulfur, charcoal and potassium nitrate (also known as saltpetre), was the original propellant employed in firearms and fireworks. It was used from about the 10th or 11th century onward, but it had disadvantages, including the large amount of smoke it produced. With the 19th-century development of various "nitro explosives", based on the reaction of nitric acid mixtures on materials such as cellulose and glycerin, a search began for a replacement for gunpowder.
Early European smokeless powders
The first smokeless powder was developed in 1865 by Johann Edward Schultze. At the time of this breakthrough, Schultze was a captain of Prussian artillery. Schultze eventually rose to the rank of colonel. His formulation (dubbed Schultze Powder) was composed of nitrolignose derived from nitrated wood grains, impregnated with saltpetre or barium nitrate.
In 1882, the Explosive Company of Stowmarket introduced EC Powder, which contained nitro-cotton and nitrates of potassium and barium in a grain gelatinised by ether alcohol. It had coarser grains than other nitrocellulose powders. It proved unsuitable for rifles, but it remained in long use for shotguns; and was later used for grenades and fragmentation bombs.
In 1884, the French chemist Paul Vieille produced a smokeless propellant that had some success. It was made out of collodion (nitrocellulose dissolved in ethanol and ether), resulting in a plastic colloidal substance which was rolled into very thin sheets, then dried and cut up into small flakes. It was immediately adopted by the French military for their Mle 1886 infantry rifle and called Poudre B (for poudre blanche, or white powder) to distinguish it from black powder (gunpowder). The rifle and the cartridge developed to use this powder were known generically as the 8mm Lebel, after the officer who developed its 8 mm full metal jacket bullet.
Based on his earlier success in developing blasting gelatin, Alfred Nobel began work in 1887/8 on trying to find an nitrated material that could be safely used as propellant to replace black powder (gunpowder) and he later patented a smokeless propellant he called Ballistite. It was composed of 10% camphor, 45% nitroglycerine and 45% collodion (nitrocellulose). Over time the camphor tended to evaporate, leaving an unstable explosive.
Nobel was also to purchase of rights of a Swedish patent obtained in May 1867, by two Swedes: Ohlsson and Norbinn, for an explosive consisting of ammonium nitrate, sawdust, powdered charcoal and a nitrated substance - Picric acid and nitroglycerine were specifically given as examples in Ohlsson and Norbinn's patent. Nobel's two Ballistite patent claims refer to the use of Celluloid, camphor, soluble nitrocellulose and the method of converting this into finished propellant. At the end of during the court case the judge concluded that Nobel was specifically distinguishing between the use of soluble and insoluble nitrocellulose; and gave detailed reasons for his decision.
Development of Cordites
thumb|upright|Sir James Dewar at work
A United Kingdom government committee, known as the "Explosives Committee", chaired by Sir Frederick Abel, monitored foreign developments in explosives and obtained samples of Poudre B and Ballistite; neither of these smokeless powders was recommended for adoption by the Explosives Committee.
Abel, Sir James Dewar and W Kellner, who was also on the committee, developed and jointly patented (Nos 5,614 and 11,664 in the names of Abel and Dewar) in 1889 a new ballistite-like propellant in 1889. It consists of (by weight) 58% nitroglycerin, 37% guncotton (nitrocellulose) and 5% petroleum jelly. Using acetone as a solvent, it was extruded as spaghetti-like rods initially called "cord powder" or "the Committee's modification of Ballistite", but this was swiftly abbreviated to "Cordite".
Cordite began as a double-base propellant. In the 1930s, triple-base propellant was developed by including a substantial proportion of nitroguanidine. Triple-base propellant reduced the disadvantages of the double-base propellant – its relatively high temperature of combustion and significant muzzle flash.
Imperial Chemical Industries's (ICI) World War II double-base propellant AN formulation also had a much lower temperature than Cordite Mk 1, but it lacked the flash reduction properties of N and NQ triple-base propellants.
Nobel and Abel patent dispute
Schuck and Solhman in their 1926 [1929] biography of Alfred Nobel specifically state that he made Paris his headquarters in 1873; and he set up an experimental laboratory there, with a young chemist as an assistant. Nobel had developed and patented a Diatomaceous earth-based Dynamite in 1875: English Patent No. 4175: ″Improved explosive (blasting gelatine or gelatine dynamite)″; and in this 1875 patent claim he specifically gives an example of using guncotton as a substance that may be used for this purpose. Dynamite had certain disadvantages: it had produced less explosive power than nitroglycerine alone, as the diatomaceous earth had a cooling effect; and as the nitroglycerine soaked into the diatomaceous earth, the dynamite ″aged″ and further reduced the explosive power compared with freshly prepared dynamite. Nobel appears to have been looking for an energetic replacement for the diatomaceous earth.
The legal suit was finally lost and a detailed judgement was given.