M V/M VII Opsiános: Difference between revisions

{{Infobox weapon|name=M6/M7 Opsiános|type=[[Main Battle Tank]]|is_vehicle=yes

|{{flagicon|Sofíae Commonwealth}} [[Sofíae Commonwealth]]

|{{flagicon|Nurmandria}} [[Nurmandria]]

{{Main|M4}}

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.

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 {{convert|70|cm}} 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.

===M6 Opsiános A ===

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 fender machine guns were removed in favour of a single bow-mounted machine gun. 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 1950, at Ulrech Svarald Tank Factory No. 183 (now [[Arlansor Armored-Vehicle Plant (ASVE)|ASVE]]). A command version was built, the M6A-ⅡI (''igesía''), with a second R-113 radio.

=== M6 Opsiános B and C===

The new tank received night vision equipment for the driver and was designated Opsiános B (''Proiókt'' 137G). 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.

A new version, based on the Opsiános B, designated Opsiános C (''Proiókt'' 137G2), was designed in 1955. It was fitted with a new 100 mm D-10T2S tank gun with STP-2 "Tsyklon" 2-plane stabilizer. It entered production in 1958. During the last four months of production, 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.

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. Kartsev combined all the ongoing improvements being offered, or planned, on the M6 into one design. This became the ''Proiókt'' 155, and entered production at Uralvagonzavod 1 January 1958 as the M7. It was accepted for service with the Red Army on 8 May. It suffered a significant lapse in one area: there was no antiaircraft machine gun, which had been present on the M6.

The Omsk OKB-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''" (NATO 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 TO-55 (''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. TO-55 flamethrower tanks were withdrawn from service in 1993.

In 1961, development of improved NBC protection systems began. The goal was to protect the crew from fast neutrons; adequate protection against gamma radiation was provided by the thick armour and a PAZ basic NBC protection system.