The MG 81 was a belt fed 7.92 x 57 mm machine gun for fixed or flexible installations in World War II Luftwaffe aircraft, replacing the older drum magazine-fed MG 15.
The MG 81 was developed by Mauser as a derivative of their successful MG34 infantry machine gun. Development focus was to reduce production cost and time and to optimize for use in aircraft. Developed in 1938/1939, it was in production from 1940 to 1945.
A special twin-mount MG 81 Z (Zwilling-twin) was introduced in 1942, which paired up two of the weapons on one mount, to provide even more firepower with max 3200 rounds/min without requiring much more space than a standard machine gun.
The MG 81 Z found itself used in some unique installations in the Luftwaffe. Some of the more known ones is a pair of MG 81 Z's installed in the hollow tail cone of the Dornier Do 217. Designated R19 (R for Rüstsätze) for the factory designed field kit, it allows the pilot of the 217 to shoot at pursuers with a hail of bullets. Another application was the "Watering can", an externally mounted pod with 3 sets of guns and ammo meant to be attached to a Junkers Ju 88 and used to strafe ground targets.