Smokeless powder

Smokeless powder is a type of propellant used in firearms and artillery that produces less smoke and less fouling when fired compared to black powder. Because of their similar use, both the original black powder formulation and the smokeless propellant which replaced it are commonly described as gunpowder. The combustion products of smokeless powder are mainly gaseous, compared to around 55% solid products (mostly potassium carbonate, potassium sulfate, and potassium sulfide) for black powder. In addition, smokeless powder does not leave the thick, heavy fouling of hygroscopic material associated with black powder that causes rusting of the barrel.

Despite its name, smokeless powder is not completely free of smoke; while there may be little noticeable smoke from small-arms ammunition, smoke from artillery fire can be substantial.

Invented in 1884 by Paul Vieille, the most common formulations are based on nitrocellulose, but the term was also used to describe various picrate mixtures with nitrate, chlorate, or dichromate oxidizers during the late 19th century, before the advantages of nitrocellulose became evident.

Smokeless powders are typically classified as division 1.3 explosives under the UN Recommendations on the Transport of Dangerous Goods – Model Regulations, regional regulations (such as ADR) and national regulations. However, they are used as solid propellants; in normal use, they undergo deflagration rather than detonation.

Smokeless powder made autoloading firearms with many moving parts feasible (which would otherwise jam or seize under heavy black powder fouling). Smokeless powder allowed the development of modern semi- and fully automatic firearms and lighter breeches and barrels for artillery.

Before the widespread introduction of smokeless powder, the use of gunpowder or black powder caused many problems on the battlefield. Military commanders since the Napoleonic Wars reported difficulty with giving orders on a battlefield obscured by the smoke of firing. Visual signals could not be seen through the thick smoke from the gunpowder used by the guns. Unless there was a strong wind, after a few shots, soldiers using gunpowder ammunition would have their view obscured by a huge cloud of smoke, and this problem became worse with increasing rate of fire. In 1884 during the Battle of Tamai Sudanese troops were able to break the square of British infantry armed with Martini–Henries because of that. Sharpshooters firing from concealed positions risked revealing their locations with a cloud of smoke.

Black powder burns in a relatively inefficient process that produces lower pressures, making it about one-third as powerful as the same amount of smokeless powder.

A significant portion of the combustion products from gunpowder are solids that are hygroscopic, i.e. they attract moisture from the air and make cleaning mandatory after every use, in order to prevent water accumulation in the barrel that can lead to corrosion and premature failure. These solids are also behind gunpowder's tendency to produce severe fouling that causes breech-loading actions to jam and can make reloading difficult.