smokeless

Smokeless powder is a type of propellant used in firearms and artillery that produces lower amounts of smoke when fired, unlike the historical black powder it replaced. The term is unique to the United States and is generally not used in other English-speaking countries, which initially used proprietary names such as "Ballistite" and "Cordite" but gradually shifted to "propellant" as the generic term.
The basis of the term "smokeless" is that the combustion products are mainly gaseous, compared to around 55% solid products (mostly potassium carbonate, potassium sulfate, and potassium sulfide) for black powder. 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. This article focuses on nitrocellulose formulations, but the term smokeless powder 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.Since the 14th century gunpowder was not actually a physical "powder", and smokeless powder can be produced only as a pelletized or extruded granular material. Smokeless powder allowed the development of modern semi- and fully automatic firearms and lighter breeches and barrels for artillery. Burnt gunpowder leaves a thick, heavy fouling that is hygroscopic and causes rusting of the barrel. The fouling left by smokeless powder exhibits none of these properties (though some primer compounds can leave hygroscopic salts that have a similar effect; non-corrosive primer compounds were introduced in the 1920s). This makes an autoloading firearm with many moving parts feasible (which would otherwise jam or seize under heavy black powder fouling).
Smokeless powders are classified as, typically, division 1.3 explosives under the UN Recommendations on the transportation 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.

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