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K31
The Karabiner Modell 1931 (officially abbreviated to Kar. 31/Mq. 31; commonly but incorrectly known in civilian circles as the 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 stripper clip can be used to load the magazine from the top of the receiver.
The Karabiner Modell 1931 replaced both the Model 1911 rifle and carbine and was gradually replaced by the Stgw 57 from 1958 onwards.
Although the Kar. 31 is a straight-pull carbine broadly based on previous Swiss "Schmidt–Rubin" service rifles and carbines, the Kar. 31 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 that previous Swiss service rifles and the Kar. 31 are chambered for. The Karabiner Modell 31 was a new design by the Eidgenössische Waffenfabrik in Bern, Switzerland under Colonel Adolf Furrer (1873–1958). The first 200 Kar. 31s 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 Modell 31 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.
The Karabiner Modell 31 barrel has 4 rifling grooves and a 270 mm (10.63 in) rifling twist rate. The action itself is only connected to the stock by two screws, one attaching to the recoil lug, with the second attaching to the tang. This allowed the Swiss to eliminate the aluminium barrel mounting collar used in the Schmidt-Rubin series. The trigger was also redesigned.
Karabiner Modell 31s are noted for their excellent accuracy and quality for a service rifle. The Swiss armed forces considered individual marksmanship to be of utmost importance. Therefore, the K. 31/Kar. 31 was made to tight tolerances and excellent overall craftsmanship. According to the Swiss Military manual for the Karabiner Modell 31 using standard issue 7.5×55mm Swiss GP 11 ball ammunition in a fixed mounting the expected accuracy of fire at a range of 300 m (328 yd) is 4 cm (1.6 in) (R50) in the horizontal (windage) axis and 6 cm (2.4 in) (R50) in the vertical (elevation) axis. Accuracy of fire at a range of 1,000 m (1,094 yd) is 21 cm (8 in) (R50) in the horizontal axis and 43 cm (16.9 in) (R50) in the vertical axis. R50 at a range means the closest 50% of the shot group will all be within a circle of the mentioned diameter at that distance. The employed circular error probable method cannot be converted and is not comparable to US military methods for determining rifle accuracy. For reference a 1 minute of arc (MOA) circle at 300 m (328 yd) has a diameter of 8.72 cm (3.4 in) and at 1,000 m (1,094 yd) has a diameter of 29.08 cm (11.4 in). When the R50 results are doubled the hit probability increases to 93.7%.
The Karabiner Modell 31 is noted for its straight-pull bolt action, meaning that the bolt handle is pulled directly rearward to unlock the action and eject the spent cartridge case in one motion, and then pushing the bolt handle forward again to chamber a new cartridge, cock the striker, and lock the action, rather than being manually turned and pulled back and forth, as in contemporary bolt action service rifles, like the German Karabiner 98k, or the British Lee–Enfield Rifle No. 4. A straight-pull bolt action reduces the range of motion by the shooter, with the goal of increasing the rifle's rate of fire.
Unlike the previous Schmidt–Rubin series of rifles, the Kar. 31's locking lugs lock up immediately behind the chamber. This forward positioning of the locking lugs affords several advantages. The entire action is strengthened as the lugs lock into the much thicker forward part of the receiver. Lock-up is also more precise.
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K31
The Karabiner Modell 1931 (officially abbreviated to Kar. 31/Mq. 31; commonly but incorrectly known in civilian circles as the 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 stripper clip can be used to load the magazine from the top of the receiver.
The Karabiner Modell 1931 replaced both the Model 1911 rifle and carbine and was gradually replaced by the Stgw 57 from 1958 onwards.
Although the Kar. 31 is a straight-pull carbine broadly based on previous Swiss "Schmidt–Rubin" service rifles and carbines, the Kar. 31 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 that previous Swiss service rifles and the Kar. 31 are chambered for. The Karabiner Modell 31 was a new design by the Eidgenössische Waffenfabrik in Bern, Switzerland under Colonel Adolf Furrer (1873–1958). The first 200 Kar. 31s 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 Modell 31 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.
The Karabiner Modell 31 barrel has 4 rifling grooves and a 270 mm (10.63 in) rifling twist rate. The action itself is only connected to the stock by two screws, one attaching to the recoil lug, with the second attaching to the tang. This allowed the Swiss to eliminate the aluminium barrel mounting collar used in the Schmidt-Rubin series. The trigger was also redesigned.
Karabiner Modell 31s are noted for their excellent accuracy and quality for a service rifle. The Swiss armed forces considered individual marksmanship to be of utmost importance. Therefore, the K. 31/Kar. 31 was made to tight tolerances and excellent overall craftsmanship. According to the Swiss Military manual for the Karabiner Modell 31 using standard issue 7.5×55mm Swiss GP 11 ball ammunition in a fixed mounting the expected accuracy of fire at a range of 300 m (328 yd) is 4 cm (1.6 in) (R50) in the horizontal (windage) axis and 6 cm (2.4 in) (R50) in the vertical (elevation) axis. Accuracy of fire at a range of 1,000 m (1,094 yd) is 21 cm (8 in) (R50) in the horizontal axis and 43 cm (16.9 in) (R50) in the vertical axis. R50 at a range means the closest 50% of the shot group will all be within a circle of the mentioned diameter at that distance. The employed circular error probable method cannot be converted and is not comparable to US military methods for determining rifle accuracy. For reference a 1 minute of arc (MOA) circle at 300 m (328 yd) has a diameter of 8.72 cm (3.4 in) and at 1,000 m (1,094 yd) has a diameter of 29.08 cm (11.4 in). When the R50 results are doubled the hit probability increases to 93.7%.
The Karabiner Modell 31 is noted for its straight-pull bolt action, meaning that the bolt handle is pulled directly rearward to unlock the action and eject the spent cartridge case in one motion, and then pushing the bolt handle forward again to chamber a new cartridge, cock the striker, and lock the action, rather than being manually turned and pulled back and forth, as in contemporary bolt action service rifles, like the German Karabiner 98k, or the British Lee–Enfield Rifle No. 4. A straight-pull bolt action reduces the range of motion by the shooter, with the goal of increasing the rifle's rate of fire.
Unlike the previous Schmidt–Rubin series of rifles, the Kar. 31's locking lugs lock up immediately behind the chamber. This forward positioning of the locking lugs affords several advantages. The entire action is strengthened as the lugs lock into the much thicker forward part of the receiver. Lock-up is also more precise.