The MG 15 was a German 7.92 mm machine gun designed specifically as a hand-manipulated defensive gun for combat aircraft during the early 1930s. By 1941 it was replaced by other types and found new uses with ground troops. History The MG 15 was developed from the MG 30, which was designed by Rheinmetall using the locking system invented by Louis Stange in the mid to late 1920s. Though it shares the MG 15 designation with the earlier gun built by Bergmann, the MG 15nA (for neuer Art, meaning new model having been modified from an earlier design) has nothing in common with the World War II gun except the model number. The World War I gun used a tipping lock system while the WWII aircraft gun uses a rotating bolt/lockring. The World War II MG 15 was used in nearly all Luftwaffe aircraft with a flexible-mount defensive position. It was a modular design with various attachments that could be quickly attached or removed. The bolt mechanism acted as a traditional open-bolt machinegun design, in which the bolt will slam forward when empty, and require re-cocking either before or after a new magazine was fitted in order to be able to fire again. The MG 15 fires from an open bolt, meaning that the bolt stays back when the gun is ready to fire, and is thus unsuitable for "through the propeller" synchronized forward firing on a fuselage mount. Pulling the trigger releases the bolt and allows it to go forward, stripping a round from the magazine. The bolt continues pushing the round into the chamber and locks up when the lockring rotates and locks the bolt and barrel extension together. At this point the trip lever releases the firing pin and the gun fires. Recoil pushes the barrel, lock and bolt backwards until the lockring hits a cam that rotates it unlocking the bolt and barrel. Inertia carries the bolt backwards until the base of the fired case hits the ejector, flinging the empty out of the receiver. If the trigger is held down the cycle will continue. If the trigger is released the bolt will remain in the rearward position. The "saddle-drum" magazine was so called because it straddled the gun, with two inversely symmetrical spiral drums that fitted on either side of the receiver. The 75 rounds of ammunition (not 150 as is often mistakenly claimed) was