In parallel with the work on the revision and putting into mass production of the T-72 "Ural" tank (object 172M), the Design Bureau of the Uralvagonzavod from 1971 to 1975 carried out development work on the Buffalo theme aimed at further improving ob. 172M. The first prototype of the vehicle was built in 1972. It was obtained by a radical conversion of one of the experimental objects 172. In total, within the framework of this work, seven prototypes of the machine were built in three designs, which received the codes "Object 172-2M" and "Object 172M-2M". The second, third and fourth prototypes were already based on the design of the 172M. Sample No. 1 managed, together with 15 experimental tanks ob.172M, to take part in large-scale tests carried out in the summer-autumn period of 1972 under the leadership of General Yu. M. Potapov. The next three copies were tested in the period 1973-74. in different regions of the country. All samples manufactured by that time in the period from June 1972 to June 1974 were tested under various climatic and road conditions and passed at least 15,000 km each, while the engines worked from 538 to 664 hours each and remained in good condition.
The main task during the work was a sharp increase in the level of performance characteristics of the machine. The implementation of the ideas led to an increase in weight to 42 tons compared to 41 tons of the 172M object. However, the increase in the mass of the car did not entail a deterioration in dynamic performance. Installation of forced up to 840 hp engine V-46F (aka B-67 later) produced by ChTZ made it possible not only to compensate for the increase in mass, but also to raise the specific power to 20 hp. per ton of weight. Forcing the engine was carried out with minimal means - reworking the supercharger design. At the same time, fuel consumption remained practically unchanged. So, in the maximum power mode, the B-67 consumed 175 g per 1 hp / h against 172 g in the same mode in the B-46 installed on the 172M rev. Coupled with a significantly increased volume of fuel tanks (additional external ones on the left fenders), this allowed not only to maintain, but also to increase the power reserve. As a result, it reached a record value of 750 km on the highway. The increase in power density also had a positive effect on the increase in average travel speed, especially over rough terrain. This was also facilitated by the introduction of a suspension with an increased dynamic travel of the rollers, hydraulic shock absorbers of increased energy intensity, experiments were carried out to change the installation scheme of torsion shafts and balancers in order to more rational redistribution of the load. The BKP were strengthened, the pressure of the working fluid in the hydraulic control system was increased.
The displacement of the engine bulkhead towards the stern, which was achieved due to some compaction of the MTO layout, made it possible to change the location of the ammo storage in the BO, increase the ammunition load from 39 rounds to 45, and make the packing more convenient. More convenient packing made it possible to carry out, when manually loading, aimed firing at a speed of up to 2 rounds per minute against 1 m. 44 sec. at object 172M (according to test data of 15 tanks about 172M in 1972).
Serious measures were taken to improve armor and structural protection.
On the case: the resistance of the VLD was improved by changing the proportions of the components of the combined protection (the thickness of the back steel sheet was increased). The installation on top of an additional steel sheet of increased hardness of a wedge-shaped section made it possible to increase the physical size of the protection in the frontal projection and to increase the angle of inclination of the VLD from 68 to 70 degrees, which in turn created more prerequisites for the rebound of modern BPS. As a result, the scheme of the VLD package looked like this: 70-mm steel + 105-mm STB + 40-mm steel at an angle of 70 °. Steel platoon screens were installed along the sides of the hull (the aft sections of the screens are made of rubber-metal), covering the side almost all the way to the level of the road wheels down and external fuel tanks to their entire height up. The spaced side protection scheme looked like this: 70-mm side + 16-mm steel screen (BO area) and 70-mm side + 5-mm steel screen (MTO area). In addition, the possibility of installing standard folding screens - "mugs", overlapping the side projection from the bow heading angles, is left.
On the tower: the improvement of protection was carried out in two stages. At the first stage, the monolithic one-piece tower had steel platoon screens in an angle of +/- 30 degrees. The side projection of the tower had external structural protection in the form of a voluminous spare parts box and a steel platoon screen installed in front of it. The aft projections of the tower were also shielded by spare parts and accessories boxes and an external obstruction (OPVT pipe, roll-up of a canvas cover, a wind shield, a canister for a cannon cannon). At the second stage, it was planned to install a cast tower with a combined filler. In general, the frontal projection of the object 172-2M provided protection against a 125-mm sub-caliber projectile with a tungsten carbide tip, which has a speed at the moment of meeting with a target of 1600 m / s. The armor of a conventional T-72 only saved from a 115-mm projectile at a speed of 1400 m / s. Protection against cumulative weapons on the front of the hull and turret increased by about 10-15% and was equivalent to 500 … 520 mm of medium hardness armor steel. The standard T-72 (tower with "corundum balls" - 1975) this figure was only 450 mm.
All vehicles were equipped with an anti-aircraft machine gun mount. The first sample had a closed-type machine-gun mount from the T-64A tank, the rest were equipped with the ZU-72 open anti-aircraft mount, standard for the T-72.
In mid-1974, tests began on an even more powerful version of the Object 172M-2M tank, with improved battlefield observation devices and a new sighting system. The 6th and 7th copies of the vehicle were equipped with a TPD-K1 laser rangefinder sight, a Buran-PA night sight, new observation devices for the commander and gunner, and a stabilizer for the Jasmin-2 cannon with an electric drive in the horizontal plane (a conventional stabilizer 2E28M had only a hydraulic drive). As soon as it was ready, the commander's observation device "Agat-T" was to be installed on the vehicle. In addition, the improved 125-mm gun 2A46M (D-81TM) was distinguished by higher accuracy due to the reduced wall thickness difference and the installation of a thermal protective casing on it. The measures taken made it possible to increase the number of hits when firing on the move at ranges of 1600 … 1800 m against targets of the "tank" type to 80-100% (according to the results of testing 15 tanks of 172M in 1972, the number of hits when firing on the move was 50, 4 %). The deviation of the midpoint of impact in height at a distance of 1 km in rain conditions was reduced by the thermal protective casing to 15 cm - versus 3.6 m without it. Additional instruments increased the commander's static angle of view from 144 to 288 degrees, and the gunner's - from 60 to 150 degrees, respectively. For tactical camouflage purposes, in addition to the TDA, a 902A "Tucha" smoke screen system was installed on the vehicle.
At the same time, in 1973-75 in the Tagil Design Bureau, a variant of a tank with a rifled 130-mm cannon 2A50 (LP-36) developed by the Design Bureau of Motovilikha Plants (Perm, chief designer Yu. N. Kalachnikov) and its smooth-bore version LP-36V was being worked out. for a 130-mm guided missile (joint proposal of NII-6 (in the last NIMI) and Nudelman Design Bureau).
However, the engines on tanks 5-7 did not work very reliably. Unlike the first four, they worked an average of just over 200 hours. The main problems were associated with the ejection of oil from the oil separator and the loss of coolant. In 1975, the designers of the ChTZ diesel engine V-67 (previously called V-46F) was urgently refined, the identified defects were eliminated. In 1976, it was planned to conduct military tests of ten tanks "Object 172-2M" and "Object 172M-2M". In the course of four years of intensive operation, ob. 172-2M and ob. 172M-2M in various road and climatic conditions, units, mechanisms and systems of tanks showed high reliability and durability, ensuring the testing and movement of the tank without speed limitation at ambient temperatures from -38 ° C to + 40 ° that took place during the tests. WITH.
Tests have shown that the service life of the V-46F / V-67 diesel engine is more than 500 hours; reinforced gearboxes, guitars, drives for a fan, a starter-generator and a compressor, a cooling system fan, support rollers, guide and driving wheels, torsion shafts, hydraulic shock absorbers - 15 thousand km; caterpillar tracks - 6, 5 thousand km in summer and 10 thousand km on frozen ground. The coefficient of unification in relation to the "Object 172M" was about 88%, so the transition to the production of a more powerful model did not require re-equipment of production shops. In the next two or three years, one could expect the adoption of the Object 172M-2M tank - an improved version of the T-72.
However, this did not happen for a number of reasons, which are rather administrative and political. Nevertheless, something from the "Object 172M-2M" already in 1975 was transferred to production vehicles: for example, reinforced gearboxes, additional viewing devices. Everything else was not in demand, and instead of starting production of "Object 172M-2M", Resolution of the Central Committee of the CPSU and the Council of Ministers of the USSR No. 1043-361 of December 16, 1976 ordered to work on the creation of a "T-72 tank with increased characteristics." The latter either repeated the existing performance characteristics of the "Object 172M-2M" (840 hp engine, laser rangefinder sight, 44 rounds of ammunition), or even inferior to it. In particular, it was proposed to leave the stabilizer of the 2E28M cannon and the TPN-3-49 night sight.
As a curiosity, mention should be made of two common legends associated with the work on object 172-2M. The first legend says that "Buffalo" (as the experimental machines were unofficially called according to the ROC code) was the prototype of the T-72 "Ural", which is fundamentally wrong, if only because ob. 172-2M was created precisely as a modernization of the object 172M, i.e. T-72 "Ural". According to the second legend, it was proposed to name the T-72 tank (ob. 172M) in the series with the name "Buffalo". The proposal allegedly came from the chief designer V. N. Venediktov. to the country's leadership, but was rejected because of its "animal" origin, which caused morally unpleasant associations with the names of foreign tanks (apparently German vehicles were implied), and was replaced by the neutral and patriotic Ural. However, this also does not correspond to reality, since again it is assumed that the Buffalo was the prototype of the Ural. The probable cause of both legends is that chronologically, work on object 172-2M was carried out simultaneously with work on object 172M, and correspondingly overlapped in the memory of the veterans. It should also be added that in conversations, memories, and sometimes in literature, exclusively associatively, it happens that "Buffalo" is mistakenly called "Bison" - they confuse animals.
Currently, the first prototype "Object 172-2M" is in the storerooms of the museum of armored vehicles in Kubinka, actually rotting in a landfill. To persistent requests to transfer it to the Uralvagonzavod Museum, GABTU responds with categorical refusals.
• Object 172-2M, the first prototype - made by converting the prototype ob. 172, in turn obtained by converting the T-64A tank
• Object 172-2M second, third and fourth prototypes - made on the basis of the construction of ob. 172M
• Object 172-2M, the fifth prototype - made on the basis of the design of ob. 172M with the installation of the V-67 engine
• Object 172M-2M sixth and seventh prototypes - made on the basis of the design of ob. 172-2M. The control system, armament were significantly improved, the 902A system was installed, the V-67 engine
• Object 172-3M - a project based on the design of ob. 172-2M with the installation of a 130-mm rifled gun 2A50 (LP-36).