K31

Swiss Karabiner Model 1931
Karabiner Model 1931 (K31) rifle
Type	Straight-pull bolt action carbine
Place of origin	Switzerland
Service history
In service	1933 to 1958
Used by	See Users
Production history
Designer	Eidgenössische Waffenfabrik
Designed	May 1931
Manufacturer	Waffenfabrik Bern
No. built	528,230
Specifications
Weight	4.0 kg (8.82 lb) empty
Length	1,105 mm (43.50 in)
Barrel length	652 mm (25.67 in)
Cartridge	7.5×55mm Swiss
Action	Straight-pull bolt action
Muzzle velocity	780 m/s (2,559 ft/s)
Effective firing range	500 m (547 yd)
Maximum firing range	5,500 m (6,015 yd)
Feed system	6-round detachable box magazine A rifle grenade launcher was available from 1944 on.
Sights	Iron sights or telescopic sight

6-round detachable box magazine

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 is chambered for the 7.5×55mm Swiss Gewehrpatrone 1911 or GP 11, a 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 and was gradually replaced by the Stgw 57 from 1958 onwards.

Although the K31 is a straight-pull carbine 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 engineer Eduard Rubin (1846–1920) was the designer of the 7.5×55mm Swiss ammunition previous Swiss service rifles and the K31 are chambered for. The Karabiner Model 1931 was a new design 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 the model number of 1931.

Compared to the previous Schmidt–Rubin series Model 1911 rifle and carbine the Karabiner Model 1931 bolt and receiver were significantly shortened, allowing for a rifle length barrel and sight radius, without increasing the overall length of the Model 1911 carbine, moving the rear sight element closer to the eye, and cutting in half the amount of time for the firing pin to strike the cartridge after the trigger was pulled.