2B1 Oka (420 mm)
An experimental model was ready in 1957. Its chassis (Object 273), was designed and built by the Kirov Plant. Its 20-meter barrel allowed it to fire 750 kg rounds up to 45 km. Due to its complexity of loading it had a relatively low rate of fire—one round every five minutes. Field tests showed various drawbacks of the entire design (the recoil was too strong for many components: it damaged drive sprockets, ripped the gear-box away from its mountings, etc.) and the sheer length rendered it incredibly difficult to transport.
Its development continued until 1960, when the idea of such overpowered guns (along with the 2A3), was abandoned in favor of tactical ballistic missiles, such as the 2K6 Luna.
Development bureau: Конструкторское бюро машиностроения (Kolomna, USSR)
Chief engineer: Boris Shavirin
Assembly plant: Kirov plant (Leningrad, USSR)
Years of production: 1957—1961
Production: 4 items
Engine: V-12-6B (diesel)
Engine characteristics: 12 cylinders; 38 880 cm³
Power: 751 HP
Max speed: 35 km/h
Range: 220 km
Fire range: 45 km
Weight: 55 t