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| weaponinfo = The Karabiner Model 1931 (K31) is a magazine-fed, straight-pull bolt action rifle. It was the standard issue rifle of the Swiss armed forces from 1933 until 1958 though examples remained in service into the 1970s. It has a 6-round removable magazine, and The K31 is chambered for the 7.5×55mm Swiss Gewehrpatrone 1911 or GP 11cartridge, a full-power rifle cartridge with ballistic qualities similar to the 7.62×51mm NATO/.308 Winchester cartridge. Each rifle included a 6-round detachable box magazine with matching stamped serial number. A charger is used to load the magazine from the top of the receiver.

The Karabiner Model 1931 replaced both the Model 1911 rifle and carbine in Swiss military service, and was would serve from the early 1930's through the Second World War and into the Cold War. The K31 began to be gradually replaced by the Stgw 57 from beginning in 1958 onwards.

Although the K31 is a straight-pull carbine design broadly based on previous Swiss "Schmidt–Rubin" service rifles and carbines, the K31 was not designed by Colonel Rudolf Schmidt (1832–1898) , as he was not alive in 1931 to do so. Mechanical Neither was mechanical engineer Eduard Rubin (1846–1920) was , the designer of the 7.5×55mm Swiss ammunition previous Swiss service rifles and the K31 are were chambered for. The Karabiner Model 1931 was a new design created by the Eidgenössische Waffenfabrik in Bern, Switzerland under Colonel Adolf Furrer (1873–1958). The first 200 K31s were made in May 1931 for troop trials (serials 500,001 – 500,200), thus which is where the model number of 1931'31' in the rifle's name originates.