Berezin UB

UB machine gun
UBS machine gun on display at the Steven F. Udvar-Hazy Center
Type	Heavy Machine Gun
Place of origin	Soviet Union
Service history
Used by	Soviet Union
Wars	World War II
Production history
Designer	Mikhail Yevgenyevich Berezin
Designed	1937–39
Specifications
Weight	21.5 kilograms (47.4 lb)
Cartridge	12.7×108mm
Action	Gas
Rate of fire	800–1050 RPM
Muzzle velocity	814 m/s (2,670 ft/s)
Feed system	Belt
Sights	Iron

Berezin UB (УБ - Универсальный Березина, Universalni Berezina, Berezin's Universal) was a 12.7 mm caliber Soviet aircraft machine gun widely used during World War II.

In 1937, Mikhail Yevgenyevich Berezin began designing a new large-caliber aircraft machine gun chambered to the 12.7 mm round used by infantry machine guns. The new design passed factory trials in 1938 and was accepted into service in 1939 under the designation BS (Березин Синхронный, Berezin Sinkhronniy, Berezin Synchronized). The rate of fire made it well suited for use as defensive armament in aircraft. While a successful design, BS was not without its faults, the biggest being its cable-operated charging which required considerable physical strength. Continued development resulted in the improved UB which came in three versions: UBK (Kрыльевой, Krylyevoi, for the wings), UBS (Синхронный, Sinkhronniy, Synchronized), and UBT (Турельный, Turelniy, for the turret), with UBS and UBK charged by compressed air. The UB was accepted into service on April 22, 1941, just two months before the start of the German-Soviet War.

The Berezin UB is a gas-operated air-cooled machine gun chambered to the Soviet 12.7×108mm infantry machine gun round. Ammunition is supplied via a disintegrating link belt with a unique system in which each new round helps to extract the spent cartridge. Another unusual feature is that the belt is advanced during the return of the moving portion of the gun and not during the recoil. Turret installations were charged manually, while wing and synchronized versions utilized pneumatic charging.

The UB in all variants was used by the vast majority of Soviet military aircraft of World War II.

A declassified 1952 US intelligence report notes that: "The Shkas was a comparatively intricate and well finished gun, the cost of which necessitated that it be kept in operating condition as long as possible by repair and replacement of parts. In contrast to the Shkas, the Beresin was deliberately expendable, that is, the Soviets' plan was to discard the entire gun after a short period of use during which one or another of the principal operating mechanisms became worn or broken." The same report notes that: "The design of the Beresin machine gun was greatly influenced by a captured Lahti 20-mm machine cannon; many features of the Finnish gun appear in all models of the Beresin."