The Object 279 Kotin was a Soviet experimental heavy tank developed at the end of 1959. This special purpose tank was intended to fight on cross country terrain, inaccessible to conventional tanks, acting as a heavy breakthrough tank, and if necessary withstanding even the shockwave of a nuclear explosion. It was planned as a tank of the Supreme Command Reserve.
The work on the tank started in 1957, which was based on a heavy tank operational requirements developed in 1956, and a pre-production tank was completed at the end of 1959. This unique tank boasted increased cross-country capability. It featured four-track running gear mounted on two longitudinal, rectangular hollow beams, which were also used as fuel tanks. The tank suspension was hydro-pneumatic with complex hydrotransformer and three-speed planetary gearbox. The track adjuster was worm-type. The specific ground pressure of this heavy vehicle did not exceed 0.6 kg/cm2 (~8.5psi). The track chain, running practically along the whole track length provided for increased cross-country capabilities on swampy terrain, soft soils and area full of cut trees, Czech hedgehogs, antitank obstacles and the like. The tank was equipped with the powerful 1000 hp 2DG-8M diesel engine, enabling the 60 metric ton tank to attain 55 km/h speed, with active range of 300 km on one refuel. It also had auto fire-fighting systems, smoke laying equipment and a combat compartment heating and cooling system.
The tank hull, with a maximum armour thickness of 269 mm, was covered by a thin, elliptical shield protecting it against APDS and shaped charge ammunition, and preventing it from being overturned by the shockwave in case of a nuclear explosion. It comprised large cast irregular shape structures of variable thickness and slope. The all-cast front part of the hull was rounded in shape with thin armour panels against HEAT projectiles, which ran around the edges of the front and sides of the hull. The sides of the hull were also cast and had similar protective armour panels. The all-cast turret, with a maximum armor thickness of 319 mm, was rounded and had anti-HEAT protective panels. The turret ring was also heavily protected. The tank was equipped with chemical, biological, radiological, and nuclear (CBRN) protection.
The tank was armed with the 130 mm M-65 rifled gun. The secondary armament was a 14.5 x 114 mm KPVT coaxial machine gun with 800 rounds. The weapons were stabilized in two planes by a "Groza" stabilizer. Object 279 carried 24 rounds of ammunition, with charge and the shell to be loaded separately. The gun was provided with a semi-automatic loading system with a rate of fire of 5-7 rounds/minute. Firing control system comprised optical rangefinder, auto-guidance system and L2 night-sight with an active infrared searchlight.
One of the reasons that this tank project was abandoned, as with other heavy tank projects, was that the Soviet military stopped operating with heavy fighting vehicles of that type, tanks and similar, as of 1960. Since then, the heaviest ones are kept at about 50 metric tons of weight, that is without counting in any extra equipment such as additional reactive armor, mine clearing devices (mine ploughs, mine rollers) etc. Furthermore, the Soviet military wanted tanks with a suitable weight for crossing their own bridges, in case of homeland defence situations similar to those that occurred during World War II, which at that time seemed to be unreliable for heavy vehicle crossings. Another reason was that a number of serious deficiencies of the running gear appeared during the trials. These deficiencies included low nimbleness, efficiency loss during swampy area crossings, complex and expensive production, maintenance and repair, and impossibility of reduction in the overall height of the tank.