AIRES Gun 7.92mm MG 81Z [German] 1:32
From Wikipedia:
The MG 81 was a German belt fed 7.92×57mm Mauser machine gun which was used in flexible installations in World War II Luftwaffe aircraft, in which capacity it replaced the older drum magazine-fed MG 15.
The MG 81 was developed by Mauser as a derivative of their successful MG 34 general-purpose machine gun. Development focus was to reduce production cost and time and to optimize the machine gun for use in aircraft. Developed in 1938/1939, it was in production from 1940 to 1945.
A special twin-mount MG 81Z (the Z suffix stands for Zwilling, meaning "twin") was introduced in 1942. It paired up two of the weapons on one mount to provide even more firepower with a maximum cyclic rate of fire of 3,200 rounds per minute without requiring much more space than a standard machine gun. Towards the end of the war many specimens were delivered to the army and equipped for use in ground battles with shoulder rest and bipod.