The Mauser 20 mm MG 151/20 is a German 20 mm aircraft cannon converted from the 15 mm MG 151/15 cannon to a 20 mm after combat evaluation proved a larger high-explosive shell to be more effective than a high-velocity shell.
| Pros | Cons |
|---|---|
| Minengeschoß shell (an improved HEI shell) provides a lot of hitting power against aircraft | Tracer and HEI (Minengeschoß) have slightly different trajectories which reiterate knowing your ammunition |
| Faster firing and less prone to jamming than the Allied Hispano variants | Ineffective against armoured ground targets, even with APHE shells |
| Higher muzzle velocity than the other German 20 mm cannons | Still lower muzzle velocity compared to most machine guns |
| Larger ammo count than the other German 20 mm cannons | Its stock belt is notoriously unreliable due to the ineffective incendiary and APHE shell |
Available ammunition
Below are listed types of vehicles this gun is available for, their belts as well as each belt’s selection of ammunition.
Aircraft offensive armament:
| Default: | IT | IT | APHE | HEI | ||
| Universal: | IT | HEI | HEI | AP-I | ||
| Air Targets: | AP-I | HEI | HEI | HEI | HEI | IT |
| Armoured Targets: | APHE | APHE | APHE | IT | ||
| Tracers: | FI-T | FI-T | FI-T | IT | IT | |
| Stealth: | HEI | HEI | HEI | APHE | AP-I |
Aircraft defensive armament:
| Default (turret): | IT | HEI | APHE | AP-I | |
| Armoured Targets (turret): | AP-I | AP-I | APHE | IT | AP-I |
| Universal (turret): | IT | HEI | HEI |
Tank commanders' armament:
| Default: | HEFI-T | AP-I |
Vessel’s main caliber gun:
| Universal: | HEFI-T | API-T | API-T | |
| 20 mm HE belts: | HEFI-T | HEFI-T | HEFI-T | API-T |
| 20 mm AP belts: | API-T | API-T | API-T | HEFI-T |
Usage in battles
The 20 mm MG 151 is very dangerous against air targets due to the Minengeschoß shell, which makes the MG 151/20 arguably the best 20 mm cannon against air targets. Unless other ammunition is needed for a specific reason, always choose the ammo belt with most Minengeschoß available. With “Air Targets” belt, it usually take a short burst of 20 — 30 rounds to take down an average fighter, 30 — 50 rounds for a heavy fighter or a ground attack aircraft, and 100 — 150 rounds for a heavy bomber.
Due to the gun’s fast rate of fire, it is quite easy to empty all of the ammo before you managed to finish the targets without proper aiming, especially without the help of gun pods. Thus, the MG 151 will often requires trigger discipline for better results, with an ace being achievable in a single sortie with a proper ammo conservation.
Despite the MG 151's stellar characteristics, the gun is also infamous due to its poor stock performances. Owing to the fact that only ¼ of its stock belt contains the “Minengeschoß” round, while the other rounds were a near-useless incendiary shell with a performance akin to that of a practice shell found on the Hispano autocannons, as well as poor APHE rounds that often over-penetrates the enemy airframe and thus were unable to detonate. Due to this, it is best to treat the stock MG 151/20 like an oversized heavy machine gun. Firing a long burst has more chance of hitting the enemy with Minengeschoß rounds until the upgraded belts are available.
History
The MG 151 was originally developed for a 15 mm cartridge which was small enough to fit between the cylinder banks of their V-12 aircraft engines and offered a higher velocity compared to the 20 mm cannons of their Allied opponents. However, in 1941, Germany recognized that, in air combat, explosive power was more important than high velocity. As a result, in 1941, the MG 151 was re-chambered to fire a 20 mm shell based on the cartridge used by the MG FF, but necked up and with a longer case body meaning that the conversion mostly involved changing the barrel.
The MG 151 was introduced on the Bf 109 F-4, would remain one of the main fighter cannons for Germany during World War II, and would be popularly exported to other nations in the Axis, such as mounting on the Japanese Ki-61-I hei, Italian Re.2005 serie 0, and Romanian IAR-81C fighters. However, Germany’s attempt to make an explosive shell for the MG 151 became its downfall. The Minengeschoß (Mine Shell) rounds were ineffective against the Allied heavy bombers taking about 15-20 hits to down one while a 30 mm cannon such as the MK 103 needed only 3 or 4 hits to down. As a result, the MK 103 and its shorter-barrelled cousin the MK 108 began to replace the MG 151 as the Luftwaffe’s (German Air Force) main cannon near the end of the war and it was adapted by the Volkssturm (German national militia) for use as an anti-aircraft weapon along with being used to upgrade the 15 mm-armed Sd.Kfz.251/21.
After the war, the MG 151 was used by the French Armée de l’Air (Air Force) and Aviation légère de l’armée de Terre (Land Army Light Aviation). In both fixed and flexible configurations, the MG 151 was used by the French in multiple aircraft including helicopters such as their H-21C Workhorse and H-34 helicopters used in Algeria. The flexible variants were modified with insulating sleeves to protect the user’s hands. The MG 151 was also used in the Portuguese and Rhodesian versions of the SA 316B Alouette III, and a variant of the cannon called the Vektor GA-1 was built by Denel in South Africa.