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Description
"Developed in 1956–1958 at the Kirov Plant, Leningrad, under the supervision of Joseph Kotin. Two prototypes were produced and underwent trials from 1959 through 1960. A hull and a turret were produced for testing for shell resistance. The development was discontinued in the summer of 1960 due to insufficient development of certain systems and components. In addition, the vehicle did not demonstrate any advantage over the Object 770 heavy tank.
The Object 277 marks the end of its Soviet heavy line.
Although the T-10 was the last of the Soviet heavy tank in series production, other heavy tank designs did follow it. Around 1955, a dual programme was begun to examine alternative heavy tanks for the future - the Obiekt 277 and Obiekt 279. The main feature shared in common was an advanced version of the 130mm gun developed for the ill-fated IS-7 heavy tank, mated to optical rangefinders for greater long-range accuracy. The new turret included an ammunition assist system for the loader, and was fitted with infra-red night fighting equipment as well. Both tanks would share a very similar enlarged turret design. However, the hull of both tanks was significantly different.

Characteristics

The Obiekt 277 was the ultimate evolution of the T-10 series and used a new cast bow, a modernised hull evolved out of the T-10 chassis, but lengthened with an additional set of road wheels. The armament consisted of a 130mm M-65 gun with a horizontal sliding breech, multiple baffle muzzle brake and bore evacuator, 'Groza' two-axis gun stabilization system, and a TPN-1 night sight. With a view to operating in a nuclear environment, a PAZ nuclear overpressure system was installed, as was a full set of night vision equipment for the turret crew and the driver. The 14.5mm KPVT co-axial machine guns could be used as a ranging weapon for the main armament. Elevation was -5° to 16° with electro-hydraulic turret traverse and manual override. The Obiekt 277 had a direct fire range of 1230m against a 2m target. In 1959 a sub-calibre APFSDS round was made available for the 130mm M-65, with a direct fire range of 2150m. The Obiekt 277 was provided with a mechanically operated ammunition carousel located in the lower turret for the separate loading two-piece ammunition, with 15 projectiles stored vertically and 15 cartridges stored horizontally. The ammunition complement was a total of 26-35 rounds. The AP rounds weighed 30.7 kg, hence the requirement for an electro-mechanical autoloader.

Development

A major issue with the tank was the length of the gun barrel. Soviet commanders were wary of guns that projected far ahead of the tank for fear that in combat the armament would strike the ground on rough terrain and thus incapacitate the gun, or worse, damage it to the point of requiring depot level maintenance not possible in combat. There was a precedent to this, in that during the trials of the SU-100 self-propelled gun there were problems with the gun barrel grounding, and SU-100 driver-mechanics had to be particularly careful in operating the vehicle. With the gun forward, the Obiekt 277 had a total length of 11.78m, so that the driver-mechanic was required to drive with considerable care, reminiscent of issues encountered with the earlier SU-100.
The glacis armour of the Obiekt 277 provided protection against 122mm rounds and 90mm cumulative rounds, although testing was not completed before the project was cancelled. Unlike the rolled homogenous armour plate glacis of the T-10 series, the Obiekt 277 used cast glacis armour. It had a maximum glacis armour basis of 140mm, set at 60-70° from vertical, with the lower glacis with the lower glacis correspondingly 153mm at 50–55° from vertical. The turret had maximum frontal armour of 290mm, with a minimum of 139mm, set at 30–60° from vertical, with maximum turret side armour of 236mm and a minimum of 138mm set at 30–55° from vertical. All in all, the Obiekt-277 was a remarkably strongly armoured tank, but that armour came at a cost relative to prescribed limits on overall heavy tank combat weight.
The Obiekt 277 was powered by an M-850 V-12 liquid cooled diesel engine developing 1090hp, created by the KB of the Zvezda Plant in Leningrad on the basis of the M-50 diesel engine used in Soviet torpedo boats, and in turn developed from the AN-1 aircraft engine. The engine was started by an S-3 electric starter developing 25hp or by means of two 5 litre compressed air cylinders. A pre-heater was provided for cold temperature starting. Fuel was 820 litres internally under armour and 250 litres externally, giving the tank a total road range of 300km with its maximum road speed of 55km/h. It used two-stage air cleaners, stage one being a ‘cyclone’ and stage two being a cassette-type oil bath cleaner. The engine and transmission were mounted as a single unit, with an 8-speed planetary transmission and ‘ZK’- type steering mechanism taken from the T-10. The final drives were provided with hydraulically assisted disc brakes. An MTO automatic fire suppression system was installed, as was a TDA-type fuel injection smoke laying system.
The tank was provided with a lengthened hull supported on eight road wheels. The torsion bar suspension was strengthened by the use of additional hydraulic recuperators and hydraulic shock absorbers on the first, second and eighth wheel stations, with bounce stops on all but the last wheel station. The tank used four return rollers. The tracks were OMSh type with internal amortization. Ground pressure was 0.73kg/cm2. Communications consisted of an R-113 radio and R-120 TPU laryngaphone. The tank was fitted with an SG-10 generator.

Trial and Failure

Two prototypes were built between 1958 and 1959, the first prototype being ready by December 1958 and tested from 7 January 1959 to 26 February 1960. An additional set of hull and turret armour was built for firing trials to determine armour integrity.
Trials showed the need for much remedial work before the tank could be accepted for production, which, combined with its long gun barrel, the fact that the tank was 5 tonnes over its design weight limit and the military and political changes in the wind by the end of the 1950s with regard to the future of heavy tanks, led to the Obiekt-277 and its M-850 diesel engine installation being cancelled by resolution of the SM SSSR dated 19 July 1960."
-Wargaming

Description
"Developed in 1956–1958 at the Kirov Plant, Leningrad, under the supervision of Joseph Kotin. Two prototypes were produced and underwent trials from 1959 through 1960. A hull and a turret were produced for testing for shell resistance. The development was discontinued in the summer of 1960 due to insufficient development of certain systems and components. In addition, the vehicle did not demonstrate any advantage over the Object 770 heavy tank.
The Object 277 marks the end of its Soviet heavy line.
Although the T-10 was the last of the Soviet heavy tank in series production, other heavy tank designs did follow it. Around 1955, a dual programme was begun to examine alternative heavy tanks for the future - the Obiekt 277 and Obiekt 279. The main feature shared in common was an advanced version of the 130mm gun developed for the ill-fated IS-7 heavy tank, mated to optical rangefinders for greater long-range accuracy. The new turret included an ammunition assist system for the loader, and was fitted with infra-red night fighting equipment as well. Both tanks would share a very similar enlarged turret design. However, the hull of both tanks was significantly different.

Characteristics

The Obiekt 277 was the ultimate evolution of the T-10 series and used a new cast bow, a modernised hull evolved out of the T-10 chassis, but lengthened with an additional set of road wheels. The armament consisted of a 130mm M-65 gun with a horizontal sliding breech, multiple baffle muzzle brake and bore evacuator, 'Groza' two-axis gun stabilization system, and a TPN-1 night sight. With a view to operating in a nuclear environment, a PAZ nuclear overpressure system was installed, as was a full set of night vision equipment for the turret crew and the driver. The 14.5mm KPVT co-axial machine guns could be used as a ranging weapon for the main armament. Elevation was -5° to 16° with electro-hydraulic turret traverse and manual override. The Obiekt 277 had a direct fire range of 1230m against a 2m target. In 1959 a sub-calibre APFSDS round was made available for the 130mm M-65, with a direct fire range of 2150m. The Obiekt 277 was provided with a mechanically operated ammunition carousel located in the lower turret for the separate loading two-piece ammunition, with 15 projectiles stored vertically and 15 cartridges stored horizontally. The ammunition complement was a total of 26-35 rounds. The AP rounds weighed 30.7 kg, hence the requirement for an electro-mechanical autoloader.

Development

A major issue with the tank was the length of the gun barrel. Soviet commanders were wary of guns that projected far ahead of the tank for fear that in combat the armament would strike the ground on rough terrain and thus incapacitate the gun, or worse, damage it to the point of requiring depot level maintenance not possible in combat. There was a precedent to this, in that during the trials of the SU-100 self-propelled gun there were problems with the gun barrel grounding, and SU-100 driver-mechanics had to be particularly careful in operating the vehicle. With the gun forward, the Obiekt 277 had a total length of 11.78m, so that the driver-mechanic was required to drive with considerable care, reminiscent of issues encountered with the earlier SU-100.
The glacis armour of the Obiekt 277 provided protection against 122mm rounds and 90mm cumulative rounds, although testing was not completed before the project was cancelled. Unlike the rolled homogenous armour plate glacis of the T-10 series, the Obiekt 277 used cast glacis armour. It had a maximum glacis armour basis of 140mm, set at 60-70° from vertical, with the lower glacis with the lower glacis correspondingly 153mm at 50–55° from vertical. The turret had maximum frontal armour of 290mm, with a minimum of 139mm, set at 30–60° from vertical, with maximum turret side armour of 236mm and a minimum of 138mm set at 30–55° from vertical. All in all, the Obiekt-277 was a remarkably strongly armoured tank, but that armour came at a cost relative to prescribed limits on overall heavy tank combat weight.
The Obiekt 277 was powered by an M-850 V-12 liquid cooled diesel engine developing 1090hp, created by the KB of the Zvezda Plant in Leningrad on the basis of the M-50 diesel engine used in Soviet torpedo boats, and in turn developed from the AN-1 aircraft engine. The engine was started by an S-3 electric starter developing 25hp or by means of two 5 litre compressed air cylinders. A pre-heater was provided for cold temperature starting. Fuel was 820 litres internally under armour and 250 litres externally, giving the tank a total road range of 300km with its maximum road speed of 55km/h. It used two-stage air cleaners, stage one being a ‘cyclone’ and stage two being a cassette-type oil bath cleaner. The engine and transmission were mounted as a single unit, with an 8-speed planetary transmission and ‘ZK’- type steering mechanism taken from the T-10. The final drives were provided with hydraulically assisted disc brakes. An MTO automatic fire suppression system was installed, as was a TDA-type fuel injection smoke laying system.
The tank was provided with a lengthened hull supported on eight road wheels. The torsion bar suspension was strengthened by the use of additional hydraulic recuperators and hydraulic shock absorbers on the first, second and eighth wheel stations, with bounce stops on all but the last wheel station. The tank used four return rollers. The tracks were OMSh type with internal amortization. Ground pressure was 0.73kg/cm2. Communications consisted of an R-113 radio and R-120 TPU laryngaphone. The tank was fitted with an SG-10 generator.

Trial and Failure

Two prototypes were built between 1958 and 1959, the first prototype being ready by December 1958 and tested from 7 January 1959 to 26 February 1960. An additional set of hull and turret armour was built for firing trials to determine armour integrity.
Trials showed the need for much remedial work before the tank could be accepted for production, which, combined with its long gun barrel, the fact that the tank was 5 tonnes over its design weight limit and the military and political changes in the wind by the end of the 1950s with regard to the future of heavy tanks, led to the Obiekt-277 and its M-850 diesel engine installation being cancelled by resolution of the SM SSSR dated 19 July 1960."
-Wargaming