The Soviet 2B1 Oka-Transformator 420mm self-propelled mortar was designed in conjunction with the 2A3 Kondensator 406mm self-propelled howitzer to integrate a super heavy artillery unit capable of firing nuclear projectiles. They were considered as strategic weapons to attack cities and large troop formations. The design of the 2B1 Oka began in 1954 and was called “Objekt 273” for its automotive part and SM.58 for its artillery part. The prototype was built in the Barrikadny Plan of Stalingrad mounting a smooth-bore breech-loading mortar of 420mm on a T-10M heavy tank chassis and was presented in 1957. The 420mm mortar grenade was called “Transformator”, weighed between 650 and 750 kg and was launched at a maximum range of 45km according to some sources, although others only granted a maximum of 25km. It could make a shot every 5 minutes due to the complexity of handling the heavy grenades used by this weapon. This mortar was removed from service in the mid-1960s with the arrival of more capable and easy to deploy artillery rockets.

2B1 OKA-TRANSFORMATOR gallery and more info


Información adicional

Ficha Completa
Country of origin

Soviet Union


Barrikadny Plant of Stalingrad


Self-propelled mortar

Entered service




Combat weight

55,300 kg

Power plant

1 x Model V.2.IS (V2K) diesel engine, 700 hp


1 x 420mm breech load mortar

Rate of fire, (maximum)

12 shells per hour

Shell weight

750 kg

Shell range

From 25 to 45 km


Total unknown, but at least 2 vehicles