On December 16, 1967, the Ministry of Defense Industry adopted Resolution No. 801, which provided for the deployment of research and development work on a new self-propelled system on a tracked chassis. It was intended to destroy concrete, reinforced concrete and earth fortifications, destroy enemy long-range artillery and installations of tactical missiles and other means of delivering nuclear charges. It was assumed that the greatest firing range should be at least 25 thousand meters, while the class of the gun and the caliber had to be chosen by the designers themselves.
The designers offered several options for installing guns on a tracked chassis:
1) the imposition of a barrel from a 180-mm towed S-23 cannon on the undercarriage of a T-55 tank with a firing range of a conventional projectile - 30 km, an active-rocket projectile - 45 km. This project received the designation "Pion-1";
2) imposition of the barrel from a 210-mm S-72 cannon on an experimental tracked chassis ("object 429") with a firing range of a conventional projectile - 35 km, an active-rocket projectile - 50 km on the chassis of an "object 429A";
3) the imposition of the barrel from the 180-mm coastal gun MU-1 (Br-402) on the chassis of the T-55 tank;
4) to place in the wheelhouse - on the undercarriage borrowed from the T-64 tank - a 203, 2-mm cannon with improved ballistic characteristics, developed by specialists from the Leningrad Kirov plant. Or a cannon of the same caliber can be openly mounted on the "Object 429", equipped with a folding opener, which improves stability when firing.
After much debate, at the beginning of 1969, it was decided to adopt the 203 mm caliber. In September 1969, the Leningrad Kirovsky plant submitted for consideration to the MOP a preliminary design for the Pion self-propelled guns based on the T-64 chassis in an open cabin design, and the Barrikady plant - an advanced design based on the object 429 chassis in an open design. As a result, it was decided to develop an ACS based on object 429 in an open design. By a joint resolution of the Central Committee of the CPSU and the Council of Ministers of the USSR of July 8, 1970, No. 427-151, it was decided to design a 203.2 mm self-propelled gun 2S7 "Pion" with a firing range of 32,000 m with conventional ammunition and 42,000 m with reactive ammunition. On March 1, 1971, GRAU approved the revised tactical and technical requirements for the projected system. They proposed to work out the possibility of using a special ZVB2 shot from the 203-mm B-4 howitzers. The maximum firing range of a conventional 110-kilogram projectile was determined at 35 km, and the minimum ricochet-free one was 8.5 km. The firing range of the active-rocket projectile was 40-43 km. The design bureau No. 3 of the Leningrad Kirovsky plant was appointed the lead developer.
The artillery unit was developed by the Volgograd plant "Barricades" under the leadership of the chief designer G. I. Sergeeva. The Volgograd artillery unit was carried out according to the classical scheme, but with some peculiarities. In particular, the barrel was not one-piece, but collapsible, consisting of a free pipe, casing, breech, coupling and bushing. Such trunks were offered back in the 70s. XIX century. specialist of the Obukhov plant A. A. Kolokoltsov. The fact is that especially powerful artillery systems are characterized by rapid wear of their rifled part when firing. In such cases, monoblocks that have fallen into disrepair are sent for replacement to special enterprises, which requires a considerable amount of time, during which the instrument is inactive. For collapsibles, a similar operation can be easily carried out in artillery workshops located in the front-line rear.
After carrying out factory and state tests, in 1975 the self-propelled gun was adopted by the Soviet Army and put into mass production. The artillery unit was produced at the Volgograd plant "Barricades". At the Kirov plant, a special chassis "object 216" was manufactured and the final assembly of the gun was carried out.
In addition to the USSR, the 2S7 was in service with Poland and Czechoslovakia (later the Czech Republic). At the moment (2010) 2S7 is in service with Russia, Ukraine, Belarus, Azerbaijan.
Self-propelled gun 2S7 is designed to perform the following tasks:
- destruction and suppression of nuclear weapons, artillery, mortars and other fire weapons and equipment;
- destruction of field and long-term defensive structures;
- suppression and destruction of rear services, points and bodies of command and control of troops and artillery;
- suppression and destruction of manpower and equipment in the areas of concentration and on the lines of deployment.
The 2S7 self-propelled gun is made according to a reckless scheme with the placement of the gun open in the rear of the tracked chassis. The 2S7 consists of a 203 mm 2A44 mechanized cannon and a tracked chassis.
The 2A44 cannon consists of a barrel, a bolt, a firing mechanism, a loading chute, a cradle, a recoil device, a pivoting and lifting mechanisms, two pneumatic pull-type balancing devices, an upper machine, sighting devices and a loading mechanism. The gun is equipped with a barrel with a casing and a two-stroke piston bolt (with a plastic seal of the "bange" type), which can be opened upwards. The shutter is equipped with a percussion-type firing mechanism, a special mechanical drive that allows automating the processes of opening and closing the shutter (in emergency mode, these operations can be performed manually), and a balancing device that facilitates opening the shutter. The firing mechanism has a socket for a capsule tube magazine. Release is carried out using an electric trigger or a release cord (in emergency mode).
A cylindrical cradle is installed on the upper machine. Attached to it are the recoil device cylinders, the toothed arch of the lifting mechanism, the recoil length sensor and the bracket for attaching the sighting devices. The recoil device includes a hydraulic recoil brake with a system for equalizing the volume of the working fluid and two hydropneumatic knurlers. Rollback length is no more than 1400 mm. The upper machine is equipped with lifting and turning mechanisms and balancing devices. The aiming of the gun in the vertical and horizontal planes is carried out using hydraulic drives or manually (in emergency mode). The angle of vertical guidance is from 0 ° to + 60 °, the angle of horizontal guidance is ± 15 ° relative to the longitudinal axis of the vehicle.
The refusal to use the muzzle brake provided a muzzle wave of low pressure at workplaces and made it possible to refuse the installation of special protection for the calculation.
The gun is equipped with a semi-automatic hydraulic loading system that allows this process to be carried out at any elevation angles of the barrel. All operations of the loading mechanism are controlled from the lock control panel. First, a projectile is placed in the charging chamber, then a propellant charge, and at the last stage (before closing the shutter) a capsule tube is manually inserted into the socket of the firing mechanism. After firing, the used capsule tube is ejected automatically when the bolt is opened.
When powered by SPG shots from the ground, a two-wheeled handcart is used. The trolley consists of a frame with wheels and a removable stretcher. The stretcher is detached when the projectile is lifted from the ground and the projectile is loaded onto the rammer tray. It is also possible to carry the stretcher manually without a trolley. An additional six people are required to supply ammunition from the ground.
The sights consist of a D726-45 mechanical sight, a PG-1M panorama, an OP4M-99A optical sight, a K-1 artillery collimator, a Sat 13-11 milestone and a Luch-S71M lighting device. ACS can fire, both from closed positions and direct fire.
For firing a cannon, caseless separate-loading shots are used, consisting of a projectile and a propellant charge (full or reduced). Powder propelling charges are enclosed in a linen shell and stored in an airtight container.
The main rounds are the OF43 high-explosive fragmentation projectile and the 3OF44 active-rocket projectile. The mass of the high-explosive fragmentation projectile is 110 kg, the mass of the explosive is 17.8 kg, the maximum firing range on a full charge is 37.5 km, the muzzle velocity is 960 m / s. The mass of the active-rocket projectile is 103 kg, the mass of the explosive is 13.8 kg, the maximum firing range is 47.5 km. Also, a concrete-piercing projectile, a special ammunition with a nuclear charge and a chemical projectile have been developed for the gun.
The ammunition load consists of 40 rounds, of which 4 are placed on a self-propelled gun, and the rest are transported in an accompanying transport vehicle.
The maximum rate of fire of the gun is 1.5 rounds per minute. The following shooting modes are provided:
- 8 shots within 5 minutes;
- 15 shots within 10 minutes;
- 24 shots within 20 minutes;
- 30 shots within 30 minutes;
- 40 shots per hour.
Additional armament includes MANPADS, RPG-7 hand-held anti-tank grenade launcher, F-1 grenades, four assault rifles and a signal pistol.
The chassis body is a welded box-section structure, which is divided by transverse partitions into four compartments: control, power, calculation and aft. In the front part of the hull there is a control compartment with three workplaces for the commander, driver and gunner, behind it is the engine compartment with the main and auxiliary power units, a compartment for four crew members and the aft compartment, which houses batteries, fuel tanks and a store. for ammunition. The cockpit is moved far forward. In addition to its main purpose, it also serves as a counterweight to the gun mount.
The undercarriage consists of front drive wheels, seven pairs of track rollers, six pairs of carrier rollers and rear idler wheels. The machine uses rubber-metal hinged tracks and an independent torsion bar suspension with telescopic hydraulic shock absorbers (on the first, second, sixth and seventh pairs of road wheels). Many parts of the undercarriage are borrowed from the T-80 tank. The mechanical transmission with a bevel gearbox and onboard gearboxes is borrowed from the T-72 tank.
For the perception of a very significant recoil force of the gun, a bulldozer-type opener is mounted in the aft part of the chassis hull. It goes deep into the ground to a depth of 700 mm and provides good stability of the gun when firing. Stability is improved by hydraulically lowering guide wheels of the tracked chassis, as well as lockable hydraulic shock absorbers for the suspension assemblies of the road wheels. At low elevation angles and when using reduced charges, the cannon can be fired without lowering the opener.
The main power plant on the self-propelled gun is a 12-cylinder V-shaped four-stroke diesel engine V-46-1 with a turbocharging capacity of 750 hp. The auxiliary power plant consists of a 4-cylinder 9R4-6U2 diesel engine with a power of 18 kW and a gearbox with a starter-generator and a hydraulic pump.
2S7 is equipped with two TVNE-4B night vision observation devices, a R-123 radio station, 1V116 intercom equipment, a fire-prevention system, filter-ventilation devices, a heating system, and a tank decontamination kit.
The gun is serviced by a crew of 14 people, of whom 7 are the crew of the self-propelled installation and are placed on the march in the control and calculation departments, and the rest are in the accompanying truck or armored personnel carrier.
