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 a mixture of nitrocellulose and nitroglycerine, and is therefore a mixture of a chemical high explosive stabilized with a low explosive. 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 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 "Devil's Porridge" munitions factory (HM Factory, Gretna) on the English–Scottish border, which produced around 800 tonnes 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 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.