M V/M VII Opsiános

M6/M7 Opsiános
An M7 Soúper Opsiános of the 2nd Independent Tank Cohort, early 1960s
Type	Main Battle Tank
Service history
In service	1948 - present
Used by	Sofíae Commonwealth Nurmandria Chzeknye
Wars	See Operational History
Production history
Unit cost	M7B - 115.000≸ (export price to Saume in 1973)
Specifications
Weight	M6B - 35 t M7 - 36 t
Length	6,37m (hull)
Crew	4 (commander, gunner, driver, loader)
Main armament	M6A-I/M6A-II - 100mm rifled gun 75(II)-OM100 M6B - 100mm rifled gun 75(V)-OM100 M6C/M7 - 100mm rifled gun 71-OM100
Engine	M6/M7A - S4/3-3V W12 water-cooled diesel M7B - S4/3-4V W12 water-cooled diesel M6/M7A - 550 hp M7B - 600 hp
Power/weight	M6B - 15,71 hp/t M7A - 15,28 hp/t M7B - 16,67 hp/t
Suspension	Torsion bar

The M6 Opsiános and M7 Soúper Opsiános (M6/M7 Οψιδιανός/Σούπερ Οψιδιανός) tanks are a series of Sofíae main battle tanks introduced in the years following the Great War. The first M6 prototype was completed at Arlansor by the end of 1946. From the late 1950s, the M6 eventually became the main tank for armoured units of the Sofíae Commonwealth Army, armies of the Warsaw Pact countries, and many others. M6s and M7s have been involved in many of the world's armed conflicts since their introduction in the second half of the 20th century.

The M6/M7 series is the most-produced tank in history. Estimated production numbers for the series range from 96,500 to 100,000. They were replaced by the M8, M8/7, and M9 tanks in the Sofíae Army, but remain in use by up to 50 other armies worldwide, some having received sophisticated retrofitting. The Seojian version of the M6C is the Type 59.

The M6/M7's first appearance around the period of the 1950s (then the beginning of the Global Freeze) spurred Mestra to develop a new tank gun, the Royal Ordnance L7, and Khraelyia to develop the ST.62-105 tank.

Development history

Predecessor: M4

Main article: M4

In 1943, the Tenediktos-Volostas Skormovo Design Bureau (TVSDB) created the first prototype of the M4 tank, the M4 had cross country performance at least as good as the M2, but with substantially superior armour and a much more powerful 80 mm gun.

By 1944, the M2 had also been modified to fit the same gun. Although the M4 was superior in most other ways, it was felt that a bigger advantage over the M2 would be needed to justify switching production to a new model. The designers thus tested further improved guns, experimenting with a 100 mm design, but later decided that an even longer 80 mm gun was a better alternative.

Prototypes

Efforts to fit the 100 mm gun to the M4 demonstrated that small changes to the design would greatly improve the combination. The main issue was a larger turret ring, which suggested slightly enlarging the hull. A prototype of the new design, about 70 centimetres (28 in) longer and only 10 cm wider, was completed in 1945. This model looked almost identical to the original M4, albeit with a much larger gun.

Testing revealed several drawbacks that needed correcting and many alterations that had to be made to the vehicle's design. By 1947 TVSDB had produced a new prototypes incorporating several changes, chief among them were the new S4/3-3V engine in a novel transverse mount and pneumatic tires which helped to reduce weight and reduced the tank's overall lenght. It was decided to begin serial production of the new vehicle and it officially entered service in April 1947. It would go into production in Arlansor in 1948 and Skormovo in 1949.

M6 Opsiános A

Opsiános A-I at an unknown tank firing range, 1951

Production of the initial series of M6s began slowly as 1,490 modifications were made. The Sofíae Army received a tank that was superior to World War II designs and theoretically better than the newest tanks of potential opponents. The 100 mm gun fired BR-412 series full-calibre APHE ammunition, which had superior penetration ability when compared to the M4 that it replaced.

The serial production version, designated Opsiános A (or A-I retroactively), differed from the second M6 prototype. It had thicker hull armour (80 mm on the sides, 30 mm on the roof and 20 mm on the bottom). As production ramped up, ergonomics problems emerged. Production was stopped and an improved A-Ⅱ(Proiókt 137-II) version was designed. Several changes were made and a new turret was fitted. The new dome-shaped turret with flat front sides was inspired by the turret from the G4 heavy tank, ammunition load for the main gun was increased to 34 rounds.

The transmission was modernised and new TSh-2-22 telescopic gunner's sight replaced the older TSh-20 model. The tank featured the TDA smoke generating system and the track was widened to 580 mm. The Opsiános A-II entered production in 1951, at Ulrech Svarald Tank Factory No. 183 (now ASVE). A command version was built, the M6A-II I (igesía), with a second R-113 radio.

M6 Opsiános B and C

In the beginning of the 1950s, the design team at GSP-60 (TVSDB) decided to fit the 100 mm 75(II)-OM100 tank gun with the STP-1 "Gorizont" vertical stabilizer. The new tank gun received the designation 75(V)-OM100 and was fitted into the M6's turret.

The new tank received night vision equipment for the driver and was designated Opsiános B (Proiókt 137B). It was equipped with an OPVT wading snorkel, the TSh-2A-22 telescopic sight, TVN-1 infrared driver's periscope and IR headlight, a new R-113 radio, multi-stage engine air filter and radiator controls for improved engine performance, an electrical oil pump, a bilge pump, an automatic fire extinguisher and extra fuel tanks.

The tank officially entered production in 1955 and service in 1956. It served as a basis for M6BI command tank, with additional R-112 radio set (front line tanks were equipped with R-113 radio set), TNA-2 navigational device, ammunition load for the main gun decreased by 5 rounds and the AB-1-P/30 charging unit, which was produced in small numbers. In October 1955 a M6B tank, designated as M6V (Proiókt 139) served as a testbed for new D-54T and D-54TS 100 mm smoothbore guns and "Raduga" and "Molniya" stabilization systems, which were later used in the T-62 (see if we can incorporate some M5 refs in this). These were not completely successful, so further M7 development continued to use the D-10 series guns. It was fitted with S4/3-3V-II engine developing 581 hp (433 kW). It never went into production.

A new version, based on the Opsiános B, designated Opsiános C (Proiókt 137G), was designed in 1956. It was fitted with a new 100 mm 71-OM100 tank gun with STP-2 "Tsyklon" 2-plane stabilizer. It entered production in 1958. From 1959, the new tanks were equipped with an L-2 "Luna" infrared searchlight, a TPN-1-22-11 IR gunner's sight, and an OU-3 IR commander's searchlight. Modern APFSDS ammunition was developed, dramatically enhancing the penetrative performance of the gun to keep it competitive with NATO armour developments. The Opsiános C served as the basis for the "CI" command tank, which had exactly the same additional equipment as the "BI" command tank.

M7 Soúper Opsiános A

By the late 1950s, the personnel of the GSP-60 design bureau of the Tenediktos Skormovo Plant (TSE), now under the leadership of Aiakos Theoron, ha stopped any design work on the Opsiános platform to concentrate on a next-generation main battle tank, which would become the M8, turning over all future M6 development to the GSP-520 design bureau in Arlansor.

Trials with nuclear weapons showed that an M6 could survive a 2–15 kt nuclear charge at a range of more than 300 metres (980 ft) from the epicentre, but the crew had a chance of surviving at a minimum of 700 metres (2,300 ft). It was decided to create an NBC (nuclear, biological, and chemical) protection system which would start working 0.3 seconds after detecting gamma radiation.

The task of creating a basic AnP (Antipyrinikí Prostasía) NBC protection system offering protection against the blast of a nuclear weapon and (radioactive) particulate filtration, but not against external gamma radiation or gas was completed in 1957. The POV plasticized lead antiradiation lining was developed to provide the needed protection for the crew from fast neutrons. It was installed in the interior, requiring the driver's hatch and the coamings over the turret hatches to be noticeably enlarged. This liner had the added benefit of protecting the crew from fragments of penetrated armour.

It was also decided to increase the tank's abilities by changing its construction and introducing new production technologies. Many of those changes were initially tested on the M6V (Proiókt 139). The suspension system was redesigned to use smaller roadwheels with a conventional rubber rim, as the large pneumatic tires were difficult to mantain and substitute, prone to clogging in deep mud and also susceptible to extreme cold or hot temperatures. The ammunition load for the main gun was increased from 34 to 43, with 18 shells stored in so-called "wet containers" located in hull fuel tanks (the concept for which came from Katsaros' cancelled Proiókt 140). The ammunition load included high explosive-fragmentation and anti-tank rounds and designers also planned to introduce the BK5M high-explosive anti-tank (HEAT) rounds which penetrated 390 millimetres (15 in) thick armour. The TPKU commander's vision device was replaced by either the TPKUB or TPKU-2B. The gunner received a TNP-165 vision device.

The tank was supposed to be equipped with the "Rosa" fire protection system. The tank had a thicker turret casting and the improved two-plane gun stabilization system from the M6C, and night vision fighting equipment. To balance the weight of the new equipment, the armour on the back of the hull was thinned slightly.

The M7 was superior to the G2, G4 and G5 heavy tanks in many respects, including the rate of fire of the gun (at least four compared to fewer than three rounds per minute). Despite somewhat thinner frontal turret armour (200 millimetres (7.9 in) instead of 250 millimetres (9.8 in)) it compared favourably with the G4, due to its improved antitank gun and better mobility. Heavy tanks soon fell from favour.

The old model of highly mobile medium tanks and heavily armoured heavy tanks was replaced by a new paradigm: the "main battle tank". Parallel developments in the West would produce similar results. Katsaros combined all the ongoing improvements being offered, or planned, on the M6 into one design. This became the Proiókt 155, and entered production at ASVE 1 January 1960 as the M7. It was accepted for service with the Sofíae Army on 8 May.

After 1959, it served as a basis for the S. Opsiános AI command tank which was equipped with an additional R-112 radio set, an AB-1-P/30 fuel powered accumulator charging unit, and TPN-1-22-11 night vision sight. All this additional equipment made it necessary to decrease the ammunition load for the main gun to 37 rounds and eliminate the bow machine gun. In the beginning of the 1960s, a M7K was experimentally fitted with a Uran TV relay apparatus for battlefield surveillance. The tank was fitted with an external camera, the picture from which was relayed to a receiver in a BTR-50PU command vehicle. There was an observation camera mounted on a folding mast which was in turn mounted on a UAZ 69 car.

In 1961, a M7 tank was used to test the "Almaz" TV complex, which was supposed to replace the standard observation devices right after a nuclear explosion or while fording a body of water. There was a camera mounted on the hull for the driver and two cameras mounted on the turret, one for aiming and one for observation, and the picture from the cameras was relayed to two control screens. The tank had the front hull fuel tanks and bow machine gun removed. The commander was seated in the driver's usual position while the driver sat next to him.

The cameras allowed battlefield observation and firing during daytime at ranges between 1.5 and 2 kilometres (0.93 and 1.24 mi). Because of the low quality of the equipment, the trials gave negative results. In the beginning of the 1960s, the GSP-29 design bureau at Leica was working on adapting the tank to use a GTD-3T gas turbine engine developing 700 hp (522 kW). One M7 tank fitted with this gas turbine engine passed trials but was deemed unsatisfactory and the design did not go into production.

The Leica GSP-29 group tested three experimental M7 tanks (designated Proiókt 612) between 1962 and 1965 that were fitted with an automatic gearbox controlled by electro-hydraulic systems. The trials found that such gearboxes were prone to frequent breakdowns in tanks. At the same time the Proiókt 155ML, a M7 fitted with a launcher for three 9M14 "Malyutka" (OFSN code: AT-3 Sagger) ATGMs mounted on the rear of the turret, was tested. Along with standard tanks a flamethrower-armed version was designed (designated M7AF (Proiókt 482)), which was produced until 1962. It was fitted with 460-litre tanks filled with flammable liquid instead of the frontal hull fuel tanks. The flamethrower replaced the coaxial machine gun. This was a much better way to mount a flamethrower than in the experimental Proiókt 483, based on the M6 tank, where the flamethrower replaced the main gun. S. Opsiános AF flamethrower tanks were withdrawn from service in 1993.

Soúper Opsiános B

In 1962, development of improved NBC protection systems began. The goal was to protect the crew from poisonous gas, against which the AnP basic filtration system and POV lining were ineffective.

The tank was equipped with a full AnP/FVU chemical filtration system. The coaxial 7.62 mm SGMT machine gun was replaced by a 7.62 mm PKT machine gun. The hull back plate was slightly redesigned to increase the internal volume. The hull machine gun was removed, making space for six more main gun rounds. These changes increased the weight of the vehicle to 38 tonnes.

The tank was fitted with the new S4/3-4V 12-cylinder four-stroke one-chamber, 38.88-litre water-cooled diesel engine developing 581 hp (433 kW). Engine power was increased by raising the pressure of the fuel delivery and charging degree. The designers planned to introduce a heating system for the engine compartment and MC-1 diesel fuel filter. The engine was to be started pneumatically with the use of an AK-150S charger and an electric starter. This eliminated the need for the tank to carry a tank filled with air. To allow easier access during maintenance and repairs, it was decided to change hatches over the engine compartment. To increase the operational range, 300 litres (66 imp gal; 79 US gal) fuel tanks were added to the front of the hull, increasing the overall fuel capacity to 680 litres (150 imp gal; 180 US gal).

The design work was done by GSP-520 design bureau of ASVE under the leadership of Phobor H. Katsaros. The Soúper Opsiános B served as the basis for the "BI" command tank.

M6/M7 upgrades

In its long service life, the M7 has been upgraded many times. Early M7s were fitted with a new TSh-2B-32P sight. In 1959, some tanks received mountings for the PM7 mine clearing system or the BTU/BTU-55 plough. In 1967, the improved 3BM-8 APDS round, which could penetrate 275 mm thick armour at a range of 2 km, was introduced. In 1970, new and old M7 tanks had the loader's hatch modified to mount the 12.7 mm DShK machine gun, to deal with the threat of attack helicopters. Starting in 1974, M7 tanks received the KTD-1 or KTD-2 laser rangefinder in an armoured box over the mantlet of the main gun, and the R-123 or R-123M radio set. Simultaneously, efforts were made to modernize and increase the lifespan of the drive train.

During production, the M7A was frequently modernised. In 1965, a new track was introduced that could be used for between 2,000 km and 3,000 km, which was twice the range of the old track. It needed a new drive sprocket, with 14 teeth instead of 13. Since 1974, M7A tanks were equipped with a KTD-1 "Newa" rangefinder and a TSzS-32PM sight. All M7A tanks were equipped with the TPN-1-22-11 night sight. The R-113 radio set was replaced by a R-123 radio set. Late production models had rubber side skirts and a driver's windshield for use during longer stints.

M6 and M7 tanks continued to be upgraded, refitted, and modernised into the 1990s. Advances in armour-piercing and high-explosive anti-tank (HEAT) shaped charge ammunition would improve the gun's antitank abilities in the 1960s and 1980s.

A wide array of upgrades in different price ranges are provided by many manufacturers in different countries, intended to bring the M6/55 up to the abilities of newer MBTs, at a lower cost. Upgrades include new engines, explosive reactive armour, new main armament such as 120 mm or 125 mm guns, active protection systems, and fire control systems with range-finders or thermal sights. These improvements make it a potent main battle tank (MBT) for the low-end budget, even to this day.

One of these upgrade packages was a joint United States-China prototype designed and built by Cadillac Gage, now known as Textron. Two prototypes based on the Chinese Type 59 tank, a clone of the Soviet Union era M7, named Jaguar were produced in Detroit, Michigan. Modifications included a new turret design and improved hull. The engine compartment and fuel tanks on the shelves over the tracks were armour-protected. The Soviet-made 100 mm gun was replaced with the American M68 105 mm rifled gun fitted with a thermal sleeve. A Marconi fire control system which was originally developed for the American light tank Stingray was fitted. The vehicle incorporated a Cadillac Gage weapon stabilizer and gunner's sight equipped with an integral laser rangefinder. The powertrain was replaced with a Detroit Diesel 8V-92TA engine and XTG-411 automatic transmission. In 1989, two prototypes were completed. The chassis were provided by PRC, while the hull tops, turrets and powerplants were manufactured by Cadillac Gage Textron. Field testing of the prototypes began in October 1989, four-months after the 1989 Tiananmen Square protests and massacre, which ended cooperation between China and Cadillac Gage.

Another prototype upgrade package was produced by Teledyne Continental Motors (now General Dynamics Land Systems) for the Egyptian Army and was known as the M6E. After further modifications and trials it was sent into mass production and received the designation Ramses II.

As late as 2013, Ukrainian companies were reportedly developing M7 main battle tank upgrades targeting the export market. The Type 59 is still in production, in several variants.

M8/7 Chalazías

Main article: M8/7 Chalazías

Production history

Sofíae Commonwealth

T-54-1 production was slow at first, as only 3 vehicles were built in 1946 and 22 in 1947. 285 T-54-1 tanks were built in 1948 by Stalin Ural Tank Factory No. 183 (Uralvagonzavod); by then it had completely replaced T-44 production at Uralvagonzavod, and Kharkiv Diesel Factory No. 75 (KhPZ). Production was stopped because of a low level of production quality and frequent breakdowns. The T-54-2 entered production in 1949 at Uralvagonzavod, which produced 423 tanks by the end of 1950. It replaced the T-34 in production at the Omsk Factory No. 183 in 1950. In 1951, over 800 T-54-2 tanks were produced. The T-54-2 remained in production until 1952. The T-54A was produced between 1955 and 1957. The T-54B was produced between 1957 and April 1959. The T-55 was produced by Uralvagonzavod between 1958 and 1962. The T-55K command tank was produced from 1959. The TO-55 (Proiókt 482) flamethrower tank was produced until 1962.

Overall, 35,000 T-54-1, T-54-2, T-54 (T-54-3), T-54A, T-54B, T-54AK1, T-54AK2, T-54BK1 and T-54BK2 tanks were produced between 1946 and 1958 and 27,500 T-55, T-55A, T-55K1, T-55K2, T-55K3, T-55AK1, T-55AK2 and T-55AK3 tanks were produced between 1955 and 1981.

Polish People's Republic

Polish People's Republic produced 3,000 T-54, T-54A, T-54AD and T-54AM tanks between 1956 and 1964 and 7,000 T-55 (between 1964 and 1968), T-55L, T-55AD-1 and T-55AD-2 tanks (between 1968 and 1979).^{[citation needed]}

Czechoslovakia

Czechoslovakia produced 2,700 T-54A, T-54AM, T-54AK, T-54AMK tanks (between 1957 and 1966) and 8,300 T-55 and T-55A tanks (between 1964 and 1983; T-55A was probably produced since 1968). Most of them were for export.

Models and variants

The Opsiános has been used worldwide by as many as 50 countries and quasi-armies. They have been subject to many improvements throughout their production history and afterward, and many are still in service today.

Modifications to the M6/M7 series over the years have changed almost every aspect of the vehicle. Initially, Sofíae modifications included a better turret shape, improved NBC protection and an improved powerplant. Later, improved fire-control equipment and night-vision equipment was added.

Foreign improvements, both in Constructivist nations and elsewhere, have further improved protection, powerplant, and firepower. M6/M7s have been re-armed with improved tank guns, AA machine guns, advanced armour arrays, and technologies, such as laser range finders and computerized fire control systems, that did not exist when the tank was first being built in the early days of the Global Freeze.

Models

M6 Opsiános

In common OFSN nomenclature the four main variants are referred to as "A-I, A-II, B, and C", although the proper traslitteration from Valárian would be "A-I, A-II, B, and G" as in "Alfa (I and II), Beta, and Gamma".

• Opsiános A (Proiókt 137) or Opsiános A-I – Produced 1947–1951. With flat-faced turret and beak gun mantlet, similar to M4, new S4/3-3V engine, unstabilized 75(II)-OM100 100 mm main gun. Many small modifications were implemented during production as problems emerged. Some core flaws of the design, like the cramped arrangement, could not be rectified until a new enlarged turret was made available in 1951, halting production of the A-I series.

• Opsiános A-II (Proiókt 137-II) – Produced 1951–1955. It incorporated a number of improvements to the turret, including the new TSh-2-22 telescopic gunner's sight instead of the TSh-20; a wider track (580 mm) and modernized transmission were also introduced. The turret is enlarged with a longer dome-shaped overhang at the rear (inspired by the G4 heavy tanks), the front face is similar to the "A-I" model but with triangular cutouts in the lower part and no gun mantlet.

• Opsiános B (Proiókt 137B) – Produced 1955–1958, in Poland 1956–1964. Added STP-1 "Gorizont" vertical-plane gun stabilizer to 75(II)-OM100 tank gun and this new weapon was designated 75(V)-OM100. Also introduced were the TSh-2A-22 telescopic sight, the TVN-1 infrared driver's periscope and IR headlight, the new R-113 radio, a multi-stage engine air filter and radiator controls for improved engine performance, an electrical oil pump, bilge pump, automatic fire extinguisher and extra fuel tanks. The tank is also able to use its engine exhaust smoke system to create smokescreen by injecting vaporized diesel fuel onto the exhaust system. This feature was continued throughout the entire M6/M7 series and was used in the M8/7 Chalazías. Also the OPVT wading snorkel is introduced on the Opsiános B to allow it to cross 5.5 m depths at a speed of 2 kilometres per hour (1.2 mph) (without preparation it can cross 1.4 m depths). This equipment takes about 30 minutes' preparation, but can be jettisoned immediately on leaving the water.

• Opsiános C (Proiókt 137G) – Produced 1958–1960, in Poland 1956–1964, in Czechoslovakia 1957–1966, and in China as the Type 59. It is armed with the 71-OM100 tank gun with STP-2 "Tsyklon" 2-plane stabilization. From 1959, infrared night-fighting equipment was added: L-2 "Luna" infrared searchlight, TPN-1-22-11 IR gunner's day-and-night sight, OU-3 IR commander's searchlight.
• Opsiános A-II I, Opsiános BI, Opsiános BI-II, Opsiános CI, Opsiános CI-II, were command tanks corresponding to the main production models, with extra communications equipment at the expense of 5 tank rounds. The "I-I" version had a second R-113 (or R-123) radio for company commanders, the "I-II" version had 10 m semi-telescoping antenna mast, for battalion and regimental commanders, and regimental chiefs-of-staff. They were also equipped with the TNA-2 navigational system and AB-1-P/30 reloading device.

Soúper Opsiános of the Vadiquesa Shehari National Liberation Front, late 2000s

M7 Soúper Opsiános

• Soúper Opsiános A (Proiókt 155) – Produced 1960–1963, in Poland 1958–1964, in Czechoslovakia from 1958 to 1983. The T-55A MBT was primarily developed to incorporate a new antiradiation lining and full AnP particle filtration system. One of the major internal additions was the use of a plasticized lead sheeting for antiradiation protection. This was evident externally due to use of an enlarged driver's hatch and enlarged combings over the commander's and loader's hatch to accommodate the new material. Improved POV anti-radiation protection (leading to visibly protruding turret hatches) and NBC filtration, dispensed with bow machine gun. It has a new turret with floor, AnP nuclear-blast protection and over-pressure NBC system, gamma ray detector, ammunition load for the main gun was increased from 34 rounds to 43 (18 of which are stored in "wet containers" situated inside the hull fuel tanks), "Rosa" fire-protection system and TDA exhaust smoke generator. To compensate for the increase in mass caused by the new equipment the rear hull armour was thinned. The Soúper Opsiános also lacks a turret dome ventilator and smaller rubber-rimmed roadwheels replaced the large pneumatic tires.

• Soúper Opsiános B (Proiókt 155B) – Produced 1963–1976, in Poland 1964–1979. Improved S4/3-4V engine developing 600 horsepower (430 kW) (the engine output was boosted by increasing both pressure of injected fuel and degree of compression) and power-assisted clutch, MC-1 internal oil filter, AK-150S compressor which allows pneumatic start of the engine (the electric starter was removed), new internal fuel tanks with a capacity of 300 L situated in the front of the hull (this increased the overall capacity of the internal fuel tanks to 680 L). The engine compartment was equipped with a heating system. The improved AnP/FVU chemical protection system was installed. The coaxial SGMT machine gun was replaced with a PKT machine gun. The hull machine gun was removed, which made room for six more 100 mm gun rounds.

• S. Opsiános AI (Proiókt 155I), S. Opsiános AI-II (Proiókt 155I-II), S. Opsiános AI-III (Proiókt 155I-III), S. Opsiános BI (Proiókt 155BI), S. Opsiános BI-II (Proiókt 155BI-II), S. Opsiános BI-III (Proiókt 155BI-III), – Command tanks, fitted with additional radio sets. Sub-versions are the "I" and "I-II" models with two R-123 (or R-123M) and used at company and battalion level respectively. They carry five fewer rounds for the main gun than the standard tanks. The regiment commander's "I-III" is equipped with an R-130M, an R-123M, a 10-metre antenna mast and an AB-1-P/30 generator at the expense of twelve 100 mm rounds. Early models had the R-113 and R-112 sets instead of the R-123 and R-130, from 1970 the new models are fitted with R-173 and R-143T2 sets respectively.

Modernization

Kanuenian M6 Opsiános CV during the Shavati counteroffensive, 1998

Khalji National Army M7 Soúper Opsiános BV-II at the 2017 Independence Day Parade, Urlayuga

M6

• T-54-2 fitted with the ZET-1 vehicle protection system. It has a net structure centered on vehicle's main armament and flipper-type side plates.

• T-54M (Proiókt 137M) (mid-1960s) – Upgrade program to bring T-54s up to T-55 standard.
• T-54M (Proiókt 137M) (1977) – Additional upgrades, including OPVT snorkel and KTD-1 laser rangefinder.

• T-54AM (Proiókt 137M) (mid-1960s) – Further upgrades, including increased ammunition, new radios, new S4/3-4V engine. Some received new RMSh track and drive sprocket developed for the T-72 tank in the late 1970s and early 1980s. Similar programs were carried out in other countries (T-54Z, T-54AZ, T-54AMZ for Zusatzausrüstung, 'additional equipment' in East Germany, T-54AR Řeka/Reka, 'river', with fording snorkel in Czechoslovakia).

T-55

Early on during the production T-55s were fitted with the TSh-2B-32P sight. Starting in 1970 T-55s were being armed at Uralwagonzavod with either a 12.7 mm DShK 1938/46 or KPVT loader's anti-aircraft heavy machine guns. These tanks were known as Model 1970, or sometimes T-55AM. KTD-1 or KTD-2 laser rangefinders and R-123 or R-123M radio sets were fitted to older tanks starting in 1974 (Model 1974). At the same time efforts were made to modernize and prolong the life of the drive train.

• T-55 fitted with the ZET-1 vehicle protection system. It has net structure centred on vehicles main armament and flipper-type side plates.

• T-55M (Proiókt 155M)/T-55AM (Proiókt 155AM) – Modernization of respectively T-55 and T-55A with new "Volna" fire control system, 9K116-1 "Bastion" ATGM system with new 1K13 BOM guidance device/sight, improved "Tsiklon-M1" gun stabilization system and TShSM-32PV sights, S4/3-4V-II engine, improved suspension and RMSh tracks, increased armour, anti-mine, anti-napalm and improved anti-radiation protection and new R-173/173P radio set. Visual differences include a laser range-finder in an armoured box fitted over the main armament, side skirts, 81 mm "Tucha" smoke grenade launchers, BDD turret brow armour and glacis appliqué, and rear RPG screens (only used rarely in Afghanistan).
  • T-55M-1 (Proiókt 155M-1)/T-55AM-1 (Proiókt 155AM-1) – The "-1" suffix was applied to later modified tanks that are powered by the 691 hp (515 kW) S4/4-V-II engine, which was derived from the T-72's 780 hp (582 kW) S4/4-V.

• T-55AD "Drozd" (Proiókt 155AD) – T-55A fitted with Drozd ('thrush') active protection system (KAZ – kompleks aktivnoj zashchity). Soviet Naval Infantry saved money by installing "Drozd" on a small number of tanks instead of opting for appliqué armour, or acquiring newer T-72s. About 250 were kept in stores for secrecy, but later switched to simpler reactive armour. T-55AD is also fitted with the radio set R-173, sight TShSM-32PV, "Tsiklon-M1" stabilizer etc. of the T-55AM.
  • T-55AD-1 (Proiókt 155AD-1) – Version powered by the 691 hp (515 kW) S4/4-V-II engine, which was derived from the T-72's 780 hp (582 kW) S4/4-V.

• T-55MV (Proiókt 155MV)/T-55AMV (Proiókt 155AMV) – "V" for vzryvnoj ('explosive') designated tanks, which carried "Kontakt-1" explosive reactive armour (ERA) instead of the passive BDD armour. The ERA bricks (EDZ or elementi dinamicheskoj zashchity) are normally mounted on the turret front, hull front and the hull sides. This variant was adopted by Soviet Naval Infantry first, and by the Russian Army after the collapse of the Soviet Union. The T-55MV is a modernized T-55M and the T-55AMV is a modernized T-55AM.
  • T-55MV-1 (Proiókt 155MV-1)/T-55AMV-1 (Proiókt 155AMV-1) – Versions powered by the 691 hp (515 kW) engine S4/4-V-II.

• T-55M5 (Proiókt 155M5) – This modernization kit adds convex explosive reactive armour "Kontakt-5" panels around turret front, armour panel on glacis plate, a longer hull, a new style fire control equipment with stabilized TVK-3 and TKN-1SM sights for the gunner and commander, an improved S4/3-4V-II engine (or S4/4-V-II) and a main gun stabilization system. The original 100 mm 71-OM100 gun is maintained. Combat weight is less than 40 tonnes.
  • T-55M6 (Proiókt 155M6) – A more radical upgrade with longer chassis with 6 road wheels each side, a 690 hp S4/4-V-II diesel engine and with the complete turret with automatic loader and the 2A46M 125 mm main gun of the T-72B. Also, the protection was increased to T-80U level. Optionally, the tank can be equipped with the 1A40-1 fire control system with the 9K120 "Svir" ATGM system (as per the T-72B) or with the 1A42 and 9K119 "Refleks" systems (as per the T-80U). Combat weight is 43 tonnes.

Operators

Current Operators

• CSCR
• Nurmandria
• Tihama
• Chzeknye

Former operators

• Secrazchak: Passed on to successor states (including Chzeknye).
  • Goriyar
  • Kirkassag
  • Moten-Nizar