MG 131 machine gun

The MG 131 (shortened from German: Maschinengewehr 131, or "machine gun 131") was a German 13 mm caliber machine gun developed in 1938 by Rheinmetall-Borsig and produced from 1940 to 1945. The MG 131 was designed for use at fixed, flexible or turreted, single or twin mountings in Luftwaffe aircraft during World War II. It was also license-built in Japan for the Imperial Japanese Navy as Type 2 machine gun.

It was one of the smallest of the heavy machine guns of the war, with a weight of 16.6 kilograms (37 lb). This was less than 60% of the M2 Browning or the Breda-SAFAT machine gun while still providing rapid fire and heavy firepower for its mass. It could fire armor-piercing, incendiary, high-explosive, and tracer ammunition. The other main Axis automatic weapon of similar caliber, the Italian Breda 12.7 mm was around 13 kg heavier and bigger, while slower by at least 150 rpm. The MG 131’s relatively small size allowed them to be mounted in the restricted space available in the nose of Luftwaffe fighters, originally designed to house the lighter caliber 7.92 mm machine guns. This became the common configuration from 1943 onwards, as the increasing armour protection of most Allied aircraft and the increasing challenge of daylight raids by heavy American bombers as the war progressed rendered the smaller caliber guns obsolescent in this role.

Lower ballistic properties that were still adequate for the task were obviously seen as an advantage: the gun was very accurate (35 x 45 cm spread at 100 m), and the barrel wore out much less quickly (barrel life of the MG 131 was 17,000 rounds), which meant that ballistic properties deteriorated more slowly.

It was installed in the Messerschmitt Bf 109, Me 410 Hornisse, Fw 190, Ju 88, Junkers Ju 388, He 177 Greif bomber variants, and many other aircraft. The Fernbedienbare Drehlafette FDL 131Z remotely-controlled gun turret system used either a single or, more commonly, a pair of MG 131s for dorsal defense. The quadmount Hecklafette HL 131V weapons "system" for tail defense, had two MG 131 guns apiece in a pair of rotating, side-mount exterior elevation carriages (the manned turret "core" provided the traverse function), was meant for standardization on many late-war prototype developments of German heavy bomber airframes, but never came to fruition beyond a small number of dimensional prototype mockups and kinetic test units.

The MG 131 fired electrically primed ammunition in order to sustain a high rate of fire when shooting through the propeller disc of a single-engined fighter. A pair of MG 131 machine guns was used as cowl armament on later models of the Bf 109G and the Fw 190.

Technical data

 * Weight : 16.6 kg
 * Length : 1.17 m
 * Muzzle velocity : ~ 750 m/s
 * Rate of fire : 900 rpm AP-API ; 930 rpm HEF-HEFI-I
 * Accuracy : 35 x 45 cm spread at 100 m
 * Barrel Life : 17,000 rounds

Ammunition specifications
The MG 131 is the sole user of the electrically-primed 13×64mm B cartridge. A mechanically-primed variant was produced in small quantities in Spain for unknown uses.