Each rifle included a 6-round detachable box magazine with matching stamped serial number.

The Karabiner Modell 31 was a new design by the Eidgenössische Waffenfabrik in Bern, Switzerland under Colonel Adolf Furrer (1873–1958).

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.

This allowed the Swiss to eliminate the aluminium barrel mounting collar used in the Schmidt-Rubin series.

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.

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.

A straight-pull bolt action reduces the range of motion by the shooter, with the goal of increasing the rifle's rate of fire.

The entire action is strengthened as the lugs lock into the much thicker forward part of the receiver.

The cocking piece doubles as a safety and is attached at the rear of the bolt sleeve assembly and secures the firing pin.

Whereas most chargers or stripper clips only held the rounds at the end of the cartridge cases, the Kar.

The charger has a guide slot wide enough for a gloved thumb to force rounds down and into the magazine in one smooth motion.

When the last cartridge from the magazine is fired, the follower comes up automatically during cycling locking the bolt open and preventing it from closing reminding the user the Kar.

Starting at 300 m (328 yd) and more distant ranges the shooter should aim below the bottom of the target, so that the front sight's post is just out of the way.

[4] The 6 o'clock hold is intended for target shooting at 300 m (328 yd), meaning the sight line is designed to let GP11 ammunition hit 30 cm (11.8 in) over the point of aim on a 60 cm (23.6 in) diameter bulls eye the Swiss military and shooting clubs used for sighting in the Kar.

Many aftermarket sights were available: Waffenfabrik Bern made the "S" and "K" (Klammer) diopter sights, Wyss makes the "W" diopter and Furter, Haemmerli and Gruenig & Elmiger made special windage and elevation fine-correctors, Sahli and many other made elevation fine correctors and these days a company by the name of Swiss Products in the United States makes a clamp-on diopter which was recently approved for use at official Swiss shooting matches.

Karabiner Modell 31s were issued with slings, muzzle caps, knife-type detachable bayonets, cleaning kits and carrying pouches for stripper clips.

The bullet drop compensation (BDC) adjustment turret is free spinning under grease friction.

At more distant ranges the shooter should aim below the bottom of the target for a 6 o'clock hold, so that the reticle's post is just out of the way.

Each full windage increment corresponds to a horizontal displacement of 45 cm (17.7 in), i.e. the width of a man at 300 m (328 yd) (1.5 mil/1.5 ‰).

55 weighs 6.1 kg (13 lb) empty with the telescopic sight mounted and has an overall length of 1,210 mm (47.64 in).

55 is tilted at an angle of approximately 15 degrees to provide room for the unimpaired loading and ejecting cartridges with the telescopic sight mounted.

The poor condition of many stocks was caused mostly by the wearing of crampons [ice-cleats that project not only from the sole but the sides of the heels] worn over hobnail boots and rifle drills that were common.

The military habit of stacking rifles in threes – often in the snow – also contributes to the 'ragged' appearance of the end of the butt.

31s can be found with "troop tags" underneath the steel butt plate at the rear end of the stock, showing its former Swiss government user.

31 recovered a small tag of plasticized paper containing the military unit, name and address and national insurance number of the Swiss citizen to whom the rifle was issued.

The Swiss method differs in that after a group of shots is fired into the target from a machine rest hits on the outer part of the target are disregarded, while only half of the hits on the inner part of the circles are counted (50% or R50), which significantly reduces the overall diameter of the groups.

Outside of Switzerland, the Karabiner Modell 31 is like other (ex) Swiss service rifles used for target shooting matches.

To celebrate its introduction in the Swiss armed forces a small commemorative batch of Karabiner Modell 31s was produced 80 years later.

Rifles with substandard locking lugs should be immediately be withdrawn from shooting and professionally repaired to prevent dangerous situations.