The MG 17 is a German aircraft machinegun that was used in many World War II Luftwaffe planes. It was based on the MG 30 light machine gun, which was also the ancestor of the MG 34 and MG 42. The MG 17 was a recoil-operated, belt-fed, air-cooled gun that fired 7.92mm Mauser rounds from a closed bolt. It had a rate of fire of about 1,200 rounds per minute and a muzzle velocity of about 900 m/s. This machinegun was effective against unarmoured planes and infantry but had limited range and accuracy. The MG 17 was first used in 1937 during the Spanish Civil War, where it proved to be superior to Republican machineguns. It was also the main gun in the early models of the Messerschmitt Bf 109E and Bf 110, as well as other planes such as the Junkers Ju 87 and Ju 88. The MG 17 was later replaced by the heavier-calibre MG 131, which had more power and penetration. Many MG 17s were modified for infantry use after being removed from the aircraft.