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Berezin UB (series)

Heavy-Caliber Aircraft Machine Gun [ 1941 ]

The Berezin UB heavy machine gun design proved a star player for Soviet aircraft during all of World War 2.

Authored By: Staff Writer | Last Edited: 10/20/2022 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

The Heavy Machine Gun (HMG) was a staple of many combat aircraft during World War II (1939-1945). Just before the fighting began, the Soviets took into service the 12.7mm (0.50 caliber) Berezin (alternatively the "Beresin) "UB" HMG series for its growing collection of modern warplanes. The weapon went on to arm such types as the Yak-1, Yak-3, Yak-7, Yak-9, Lavochkin La-5, and the classic Ilyushin IL-2 "Sturmovik" (rear gunner mount), such was its historical reach.

The gun saw design work by Mikhail Berezin begin around the latter 1930s as an effort to develop a simpler, synchronizer-capable aerial machine gun solution using the same large-caliber cartridge as ground-based, in-service Soviet HMGs. Work began in 1937 leading to trials undertaken by way of the prototype Berezin "BS" in 1938. This then led to a quantitative order had in 1939 but progress slowed some by ongoing testing delays into the early part of 1941. Evaluations ultimately led to improvements that produced the satisfactory introductory "UB" model of April 1941 which headlined a whole series of related machine guns (the UBS, UBK, and UBT).

The gun was available in limited numbers by the time of the German invasion of the Soviet Union that same year but the invasion forced mass production to ensue thereafter.

This aerial weapon was chambered for the 12.7x108mm rimless heavy cartridge and fired from a gas-operated internal action fed by belted (disintegrating link belt) ammunition of 250-round count. To prevent overheating and fracturing / deforming of the barrel assembly, a simple air-cooled approach was utilized. Rate-of-fire ranged between 800 to 1,050 rounds-per-minute depending on application and regulator setting while muzzle velocity of the outgoing bullet was 2,670 feet-per-second. Sighting of the gun accomplished through a simple iron arrangement either in the cockpit (fixed, forward-firing installations) or over the gun (trainable mountings). Charging of the weapon also differed depending on the application: as a defensive-mounted, trainable machine gun solution, the operator simply managed the exposed charging handle as normal; for buried aircraft mountings, a pneumatic arrangement was featured.

Overall length reached up to 55 inches (UBT) with the barrel assembly measuring 35 inches long.

The outward appearance of the gun was rather utilitarian if streamlined and compact. There were three cylinders stacked ahead of the receiver, one of these being the barrel assembly itself. The receiver was rectangular in its general shape and housed the pertinent internal action as well as the feed and ejection ports.

Both the UBS and UBK were fixed aircraft machine guns typically embedded into portions of the airframe. The UBS differed in being synchronizer-capable (i.e., firing through a spinning propeller blade) while both versions were pneumatically charged by the operator. The UBK was the version fitted to trainable mountings (including turrets) and these had a manually-charged action.

Approximately 130,000 units of the Berezin design were produced during the war years which, in turn, promoted widespread use of this well-made and reliable aircraft machine gun. A dimensionally larger form, the Berezin "B-20", served as an automatic cannon but retained many of the same internal principles that made the Berezin machine gun form a success.©MilitaryFactory.com
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State Factories - Soviet Union
China; North Korea; Soviet Union
Operators National flag of China National flag of North Korea National flag of the Soviet Union
Service Year
Soviet Union
National Origin

Capable of suppressing enemy elements at range through direct or in-direct fire.

1,347 mm
(53.03 inches)
Overall Length
890 mm
(35.04 inches)
Barrel Length
47.29 lb
(21.45 kg)
Empty Weight
Gas-Operated; Full-Automatic-Only
Rounds are automatically ejected from the breech, a new cartridge stripped from the feed and set in the chamber, and rounds are continuously fired so long as the trigger is pulled and an ammunition supply exists.
Gas-operated system is featured, typically involving a gas cylinder and rear-driven piston directing energy to the bolt component.
12.7x108mm Rimless
May not represent an exhuastive list; Calibers may be model-specific dependent; Always consult official manufacturer sources.
250-round disintegrating belt.

Material presented above is for historical and entertainment value and should not be construed as usable for hardware restoration, maintenance, or general operation - always consult official manufacturer sources for such information.

2,670 ft/sec
(814 m/sec)
Muzzle Velocity

UB -Base Series Designation.
BS - Initial prototype form of 1939.
UBK - Embedded aircraft gun (fixed-forward mountings).
UBS - Embedded aircraft gun (fixed-forward mountings); synchronzer-capable.
UBT - Ring-mounted gunner's variant; manual charging.

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