The Smith & Wesson Model 1940 Light Rifle is a short-lived American rifle.
In early 1939, the British government asked Smith & Wesson to design a light rifle firing the ubiquitous 9×19mm Parabellum cartridge for their use, and advanced one million dollars toward production of the design following receipt of prototypes assembled in accordance with a patent application filed on 28 June 1939. After the rifles were delivered, testing the Royal Small Arms Factory revealed that the rifle had been designed for cartridges as loaded by United States civilian cartridge companies, and not by the cartridges loaded by the Britons; this design caused broken receivers in the weapon after as few as 1000 rounds fired. The British government required a major redesign with the weapon so that it could fire 5000 rounds without any stoppages, jams or failures, and as such, a sleeve was added to the receiver to help strengthen it and meet the requirement. Rifles with the strengthened sleeve are designated as Mark II rifles, while unmodified rifles are known as Mark I variants. After receiving 60 prototypes and 950 production rifles, the British army completely cancelled the production contract. Most of the light rifles were cut in half and dumped at sea when World War II ended, though five were saved and are in display around various museums in the United Kingdom.
Smith & Wesson continued production of the rifles with serial numbers as high as 2200 and the rifle was tested by the United States Army at Aberdeen Proving Ground, where the company hoped for the rifle to have some use. However, the United States army rejected the design as well, as it used a non-standard military cartridge for the military at the time. There was some discussion about a redesign of the weapon to permit full-automatic fire, but these plans never came to fruition as Smith & Wesson stopped production of the weapon entirely after producing 1227 rifles. The weapons were considered unsuitable for sale to civilians under the National Firearms Act, so 217 samples remained at the Smith & Wesson factory until a dealer negotiated the Curio and Relic Firearms status with the Bureau of Alcohol, Tobacco, Firearms and Explosives in 1975. With the negotiation, collectors came and purchased 137 of the 217 rifles.