Cordite

Cordite is a family of smokeless propellants developed and produced in the United Kingdom from 1889 to replace gunpowder as a military propellant. Like gunpowder, cordite is classified as a low explosive because of its slow burning rates and consequently low brisance. These 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 enough to destroy the barrel of the firearm, or gun.

Cordite was used initially in the .303 British, Mark I and II, standard rifle cartridge between 1891 and 1915; however, shortages of cordite in World War I led to United States–developed smokeless powders being imported into the UK 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 2-and-3-inch-diameter (51 and 76 mm) 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.

The term cordite generally disappeared from official publications between the wars. However, during World War II double based propellants were very widely used and there was some use of triple based propellants by artillery. Triple based propellants were used in post war ammunition designs and remain in production for UK weapons; most double based 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 For small arms it has been replaced by other propellants, such as the Improved Military Rifle (IMR) line of extruded powder or the WC844 ball propellant currently in use in the 5.56×45mm NATO.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.