MG 15 machine gun

MG 15 machine gun
MG 15 in left beam mounting inside a Ju 52, and above it storage brackets for 12 MG 15 magazines, with one magazine mounted.
Type	Machine gun
Place of origin	Nazi Germany
Service history
Used by	Nazi Germany Imperial Japan (Type 98)
Wars	World War II
Production history
Designer	Theodor Bergmann
Designed	1920s
Manufacturer	Bergmann (Weimar Republic), Rheinmetall (Third Reich)
Variants	Modular design Type 98 (Direct Japanese copy)
Specifications
Weight	12.4 kg (27 lb) loaded with gunsight and cartridge bag
Length	1,078 mm (42.4 in) (without attachments)
Barrel length	690 mm (27 in)
Cartridge	7.92×57mm Mauser
Caliber	7.9mm
Action	Recoil
Rate of fire	1,000 - 1,050 rpm
Muzzle velocity	755 m/s (2,480 ft/s)
Feed system	75-round double-drum magazine
Sights	Various types

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.

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. Operation was easy and the bolt remained in the cocked position after expending the 75 round double drum (also called a "saddle drum") magazine, negating the need to re-cock once a fresh magazine was installed.

The MG 15 fires from an open bolt, meaning that the bolt stays back when the gun is ready to fire, and also making it nearly impossible 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 75 rounds of ammunition was evenly distributed in each side of the magazine with a central feed "tower" where the ammunition is fed to the bolt. Various methods where used to secure the magazines in the aircraft, while a carrier of 3 mags each were used on ground. Ammunition was fed by a spring forced spiral double-drum containing 75 rounds total (not 150 as is often mistakenly claimed). This combined with a firing rate of 1000+ rpm means it could empty the magazine in 4.5 seconds or less. Typical practice was to provide at least 10 reloads for each gun on the aircraft, not including the magazine on the gun.