B-20
Second from the top in the middle
Type	Autocannon
Place of origin	USSR
Service history
In service	Soviet Air Forces, Soviet Air Defence Forces
Wars	World War II, Korean War
Production history
Designer	Mikhail Yevgenyevich Berezin
Designed	1944
Specifications
Mass	25 kg (55 lb)
Length	2,035 mm (80.1 in)
Barrel length	1,588 mm (62.5 in)
Cartridge	20×99mm
Caliber	20 mm (0.8 in)
Barrels	1
Action	Gas
Rate of fire	800 rounds/min (600 synchronized)
Muzzle velocity	790–815 m/s (2,590–2,670 ft/s)

The Berezin B-20 (Березин Б-20) was a 20 mm caliber autocannon used by Soviet aircraft in World War II.

Development

The B-20 was created by Mikhail Yevgenyevich Berezin in 1944 by converting his 12.7 mm Berezin UB machine gun to use the 20 mm rounds used by the ShVAK cannon. No other changes were made to the weapon which was pneumatically or mechanically charged and was available in both synchronized and unsynchronized versions. In 1946, an electrically-fired version was created for the turrets of the Tupolev Tu-4 bomber until the Nudelman-Rikhter NR-23 cannon became available. The B-20 was a welcome replacement for the ShVAK because it was significantly lighter - 25 kg (55 lb) to the 40 kg (80 lb) ShVAK - without sacrificing rate of fire or muzzle velocity.

Specifications

• Ammunition: 20×99mm
• Empty weight: 25 kg (55 lb)
• Muzzle velocity: 750–770 m/s (2,460-2,525 ft/s)
• Rate of fire: 800 rounds/min
• Mass of one-second burst: 0.95 kg (2.1 lb)

Production

The Soviet archives register the following production numbers by year:^[1]

• 1944 — 2,275
• 1945 — 7,240
• 1946 — 440
• 1947 — 780
• 1948 — 1,686
• 1949 — 2,931