The Cold War pushed the Soviet defense industry to develop unique types of weapons that, even after 50 years, are able to excite the imagination of the layman. Everyone who would be in the artillery museum in St. Petersburg was probably amazed at the size of the 2B1 Oka self-propelled mortar, which is one of the most interesting exhibits on display. This 420-mm self-propelled mortar, designed in the USSR in the mid-50s of the last century, is the largest mortar in the history of mankind. Moreover, the concept of its use assumed the use of nuclear weapons. A total of 4 prototypes of this mortar were made, it was never mass-produced.
Work on the creation of a powerful 420-mm mortar was carried out in parallel with the development of a 406-mm self-propelled gun 2A3 (code "Condenser-2P"). The chief designer of the unique self-propelled mortar was B. I. Shavyrin. The development of the mortar began in 1955 and was carried out by well-known Soviet defense enterprises. The development of its artillery unit was carried out by the Kolomna Special Design Bureau of Mechanical Engineering. The design bureau of the Kirovsky plant in Leningrad was responsible for the creation of a self-propelled tracked chassis for a mortar (object 273). The development of the 420-mm mortar barrel was carried out by the Barrikady plant. The length of the mortar barrel was nearly 20 meters. The first prototype 2B1 "Oka" mortar (code "Transformer") was ready in 1957. Work on the development of the self-propelled mortar "Oka" continued until 1960, after which, according to the decree of the USSR Council of Ministers, they were stopped. The designations "Condenser-2P" and "Transformer" were used, among other things, for the purpose of misinforming a potential adversary about the true purpose of the development.
The undercarriage of the car, designed by the Kirovsky plant design bureau, according to the GBTU classification, received the designation "Object 273". This chassis was maximally unified with the ACS 2A3 and met the increased requirements for structural strength. This chassis used the power plant from the Soviet T-10 heavy tank. The chassis of the self-propelled mortar "Oka" had 8 double track rollers and 4 supporting rollers (on each side of the hull), the rear wheel was the guide wheel, the front wheel was the leading one. The guide wheels of the chassis had a hydraulic system for lowering them in a combat position to the ground. The suspension of the chassis was a torsion beam with hydraulic shock absorbers, which were able to absorb a significant part of the recoil energy at the time of a mortar shot. However, this was not enough. The absence of recoil devices on the mortar also affected. For this reason, when a 420-mm mortar was fired, it drove back on tracks to a distance of up to 5 meters.
During the campaign, the self-propelled mortar was controlled only by the driver, while the rest of the crew (7 people) was transported separately in an armored personnel carrier or truck. In the front part of the body of the machine was located MTO - the engine-transmission compartment, in which a 12-cylinder liquid-cooled diesel engine V-12-6B was installed, equipped with a turbocharging system and developing a power of 750 hp. There was also a mechanical planetary transmission, which was interlocked with the swing mechanism.
As the main armament on the mortar, a 420-mm smooth-bore mortar 2B2 with a length of 47.5 calibers was used. The mines were loaded from the breech of the mortar using a crane (mine weight 750 kg), which negatively affected its rate of fire. The mortar rate of fire was only 1 shot in 5 minutes. The 2B1 Oka mortar carried ammunition included only one mine with a nuclear warhead, which guaranteed at least one tactical nuclear strike under any circumstances. The angle of vertical guidance of the mortar lay in the range from +50 to +75 degrees. In the vertical plane, the barrel moved thanks to the hydraulic system, at the same time, the horizontal guidance of the mortar was carried out in 2 stages: initially, a rough adjustment of the entire installation and only after that guidance to the target with the help of an electric drive.
In total, 4 2B1 Oka self-propelled mortars were assembled at the Kirov plant in Leningrad. In 1957, they were shown during the traditional military parade, which took place on Red Square. Here, at the parade, the mortar was also seen by foreigners. The demonstration of this truly huge weapon created a real sensation among foreign journalists, as well as Soviet observers. At the same time, some foreign journalists even made the assumption that the artillery installation shown at the parade is only a props, which is designed to produce a frightening effect.
It is worth noting that this statement is not so far from the truth. The vehicle was more indicative than combat. During the tests, it was noted that when firing ordinary mines, sloths could not stand, the gearbox was torn from its place, the chassis structure was destroyed, and other breakdowns and shortcomings were also noted. Refinement of the self-propelled mortar 2B1 "Oka" went on until 1960, when it was decided to finally stop work on this project and the self-propelled gun 2A3.
The main reason for the curtailment of work on the project was the emergence of new tactical unguided missiles that could be installed on lighter tracked chassis with better cross-country ability, which were cheaper and much easier to operate. An example is the 2K6 Luna tactical missile system. Despite the failure with the Oka mortar, Soviet designers were able to use all the accumulated experience, including negative, in the design of such artillery systems in the future. This, in turn, allowed them to reach a qualitatively new level in the design of various self-propelled artillery installations.
Specifications 2B1 "Oka":
Dimensions: length (with the gun) - 27, 85 m, width - 3, 08 m, height - 5, 73 m.
Weight - 55, 3 tons.
Reservation - bulletproof.
The power plant is a V-12-6B liquid-cooled diesel engine with a power of 552 kW (750 hp).
Specific power - 13.6 hp / t.
The maximum speed on the highway is 30 km / h.
In store down the highway - 220 km.
Armament - 420-mm mortar 2B2, barrel length 47, 5 calibers (about 20 m).
Rate of fire - 1 shot / 5 min.
The firing range is up to 45 km, using active-reactive ammunition.
Crew - 7 people.
