History
The gun was developed by Rheinmetall-Borsig in 1940 and presented to the Reich Air Ministry, in response to an order to develop a large-caliber aircraft gun to combat Allied heavy bombers. Tests showed that the gun was very well suited for this purpose: an average of four hits was enough to cut in half a heavy bomber, for example, "B-17" or "B-24". For the same, to shoot down a single-engine fighter, a single hit is enough. By comparison, the 20mm MG 151/20 gun required an average of 20 to 30 hits to shoot down the B-17.
The MK 108 was put into production in late 1941. The peak production in September-October 1944 was 10,000 units per month. The gun received its first combat use at the end of 1943 on Messerschmitt Bf 110 (G-2 / R3) fighters.
Construction
The gun proved to be effective and reliable, while relatively lightweight, compact and easy to manufacture. This was achieved by the simplicity of the design - 80 percent of all parts were made by stamping, the number of moving parts was minimized by the use of a free-bolt circuit. Such automation, however, had its drawbacks.
Automation
Automatics with free movement of the bolt are simple, but are usually used only in light small arms (for example, in submachine guns PPSh, MP-40, etc.[Note 1]. The reason is that at higher pressures in the barrel, characteristic of medium-caliber systems, the release of gases when opening the bolt can damage the weapon. Therefore, in such systems, other automation schemes are usually used: recoil of the barrel or removal of powder gases. These automatic schemes, in addition, allow you to achieve a higher pressure in the barrel channel, which is important for achieving good ballistics of the weapon. The designers of the MK 108 still used a free shutter, which made it possible to simplify and simplify the design; the problem of gas emission was solved by shortening the barrel. The length of the barrel was calculated in such a way that by the time the bolt was opened, the projectile had already left the barrel channel and the pressure of the gases in the barrel had dropped to a safe level. This decision came at a price. Due to the shortening of the barrel, the initial velocity of the MK 108 projectile was noticeably lower than that of other aircraft guns, which had a negative impact on ballistics: the effective firing range decreased and the spread of shells increased. However, as the practice of combat use has shown, the compromise was very successful. For comparison, we point out that the 30-mm gun "MK 103" with the usual automatic scheme and high speed of the projectile had a weight of 145 kg and a length of more than 2 m, so it was not used on single-engine fighters.
Disadvantages
The low muzzle velocity of the projectile became the main drawback of the MK 108, as it worsened the flattening of the trajectory (the reduction of the projectile is 45 m in the first 1000 m of flight)[source not specified 1892 days]. The long flight time of the projectile and the arcuate trajectory seriously limited the effectiveness of fire on maneuvering targets, so the gun was intended for use against bombers. But even heavy aircraft had to be fired from short ranges, which was difficult on fast fighters such as the Me 262, which risked colliding with the target when attacking at high speed.
Ammunition
30mm ammo. JPG
The MK 108 gun used specially designed 30 mm cartridges with a case length of 90 mm. Unlike most other ammunition that used brass for the cartridges, the MK 108 used steel cartridges. Various types of ammunition were developed: armor-piercing, high-explosive and incendiary. In practice, high-explosive and incendiary shells were most often used. High-explosive shells were made of steel by deep drawing, and not by turning the hull, as in most cases. This made it possible to obtain a thin-walled, but durable body, in which much more explosive or incendiary mixture was placed than in a shell with a chiseled body. Hence the German name of the projectile is "Minengeschoß", that is, a projectile with an increased filling of explosives. In addition, the pulled body was lighter than the chiseled one, which favorably affected the operation of the selected automation scheme.
The gun was equipped with a belt of 60[2] or 120 rounds.
Combat use in aviation
The MK 108 gun was widely used on fighters operating against Allied heavy bombers, among whose crews it quickly earned a reputation as a formidable and crushing weapon. Because of the characteristic sound of the shot and the high rate of fire, she was nicknamed[who?] "jackhammer".
The gun was also widely used on twin-engine night fighters ("Heinkel He.219", "Messerschmitt Bf.110"), on which it was mounted both in the usual way and in the middle of the fuselage at an angle up and forward. This installation was called "Oblique Music" (German: Schräge Musik); it allowed fighters to attack enemy bombers stealthily, approaching them from below, in the "dead zone" of the rear gunner.
Four MK 108 cannons were armed with the luftwaffe's first jet fighter, the Messerschmitt Me 262.
