The Winchester Model 40 was a short-lived American 12 gauge self-loading shotgun manufactured by the Winchester Repeating Arms Company from 1940 to 1941. Winchester's second self-loading shotgun design, the Model 40 was Winchester's unsuccessful attempt at re-entering the semi-automatic shotgun market.
The design heritage of the Model 40 dates back to 1911 with the Model 1911, Winchester's previous offering catered to the semi-automatic shotgun market, which was the result of attempts to sidestep as many of John Browning's patents he held on his shotgun as possible. The Model 1911 was not a commercial success with some 82,774 produced and made a name of itself as a design failure.
By the 1930s, sales of semi-automatic shotguns by Winchester's competitors were booming; this spurred Winchester all the more to create a self-loading shotgun that could immediately be competitive with other offerings from its competitors. This new shotgun would be known as the Model 40. The shotgun was introduced in Winchester's 1940 catalog.
After its introduction, Winchester attempted to sell the firearm through an advertising campaign; the Model 40 was touted as being a streamlined design that incorporated a number of new features and was very smooth to operate. However, despite Winchester's best efforts, the Model 40 was commercially unsuccessful, even more so than its predecessor, mainly due to a number of design flaws.
With the firearm being commercially unsuccessful, along with reports of design flaws with the shotgun, Winchester decided to not refine the design further and stopped production the next year in 1941. After stopping production of the Model 40, Winchester issued a recall of the firearm, although many owners of Model 40s did not take advantage of the recall; reportedly, owners who did send in their Model 40s received not a repaired Model 40 from Winchester, but a Model 12 instead, along with a note telling them to "forget about Winchester making a semi-automatic shotgun", with Winchester converting most of their tooling for the war effort.
The Model 40s recalled by the Winchester factory were presumably disposed of, apparently through lining them up on railroad tracks and having them run over by passing trains.
In essence, the Model 40 is a long recoil-operated semi-automatic shotgun, where the barrel and bolt are locked together when the bolt moves to the rear, with the barrel unlocking later on when a new cartridge is chambered; a coiled spring brings the barrel back into battery after it fires.
The Model 40 was heavily based on the Model 1911, but featured an actual side charging handle due to the expiration of Browning's patents. As it was based on the Model 1911, the Model 40 suffers from almost all the same faults, such as splitting stocks when the fiber washers acting as recoil rings wore off causing excess recoil. The weapon uses a four-round tube magazine.