The history of Soviet light self-propelled artillery installations is inextricably linked with the city of Gorky, present-day Nizhny Novgorod. It was here that artillery systems were developed and built, which were installed on light Soviet self-propelled guns. The ZIS-30, the first mass-produced Soviet light self-propelled gun of the war period, was also created and produced here. The head production of T-60 and T-70 tanks was also located in Gorky, on the basis of which self-propelled units were developed. It is not surprising that the design bureau of the Gorky Automobile Plant named after Molotov eventually also joined in the creation of the SPG. The GAZ-71 and GAZ-72 vehicles developed here, which will be discussed in this material, under a certain set of circumstances could well become the main light SPGs of the Red Army.
Forced competition
Works on the line of self-propelled units for GAZ im. Molotov can be considered not quite profile. The plant already had enough worries about its main field of activity. In the spring of 1942, there was a transition from the production of the T-60 to the much more advanced T-70 light tank. This is not the first vehicle created in Gorky: back in 1936, under the leadership of V. V. Danilov, a reconnaissance amphibious tank TM ("Molotov tank") was developed here, a very remarkable vehicle equipped with a pair of GAZ AA engines. But TM did not advance further than the prototype. But the GAZ-70, aka T-70, turned out to be a real lifesaver for the Soviet tank building and for the Red Army. Thanks to this machine, it was finally possible to bridge the gap in the tank armament system, formed after the failure to launch the T-50 light tank into series.
Of course, in terms of the aggregate characteristics, the T-50 was superior to the T-70, but they usually fight with what they have. The T-50 never made it into a large series, and the T-70 was maximally focused on production capabilities during the war period. It is not surprising that this tank became the second largest Soviet wartime tank after the T-34. In addition, the T-70 base proved to be successful for the development of SPGs.
During the first half of 1942, Sverdlovsk was the main center for the development of medium ACS. Factory No. 37 was evacuated there at the end of 1941. Department No. 22, revived in a new location, in addition to the current work on mastering the production of T-30 and T-60, from the spring of 1942 worked on the creation of light self-propelled units. The design bureau worked closely with SA Ginzburg, implementing his concept of a "universal chassis" based on the T-60. It is from this concept that the SU-31 and SU-32 SPGs originate.
One of these machines could well have gone into production, but fate wanted to decide otherwise: on July 28, 1942, GKO decree # 2120 was issued “On organizing the production of T-34 tanks at Uralmashzavod and plant # 37 of the Narkomtankoprom”. According to this document, plant number 37 was part of the Ural Heavy Machine Building Plant (UZTM), and the production of light tanks at its facilities was stopped. This meant that work on light SPGs in Sverdlovsk also stopped. The developments on the SU-31 and SU-32 were transferred to the plant number 38 in Kirov, where Ginzburg began to work in close cooperation with the factory design bureau under the leadership of M. N. Shchukin.
Tests of the SU-31 and SU-32 continued until September 1942. Based on their results, the choice was made in favor of chassis "31" with parallel placement of GAZ-202 engines. It was this scheme that was taken into operation at Plant No. 38. On the other hand, the Main Artillery Directorate (GAU) and the Main Armored Directorate (GABTU) of the Red Army decided to play it safe. Serious delays occurred in all areas of the development of Soviet SPGs. At this moment, the idea arose to involve in the program for the creation of light ACS KB GAZ them. Molotov. The tank direction there was headed by Deputy Chief Designer N. A. Astrov. At that moment, the design bureau was working on the modernization of the T-70, but did not refuse from the urgent task from above. Thus, work began on another machine. If the design bureau of factory # 38 and Ginzburg failed, it would become the very SU-76 that the troops were waiting for.
We'll go the other way
The tactical and technical requirements (TTT) for self-propelled artillery installations were developed by October 16, 1942. They did not reinvent the bicycle at the top and in many respects repeated the requirements for the SU-31 and SU-32. Even in terms of the layout, TTTs repeated the machines built in Sverdlovsk. For example, the "76-mm assault self-propelled unit" was based on the chassis, which was developed using T-70 units. This meant that it used a twin GAZ-203 engine. It looks very curious, especially against the background of the fact that the GAU rejected such a scheme, since such a power plant on the SU-32 overheated. Head of GAU Colonel-General ND Yakovlev and Deputy People's Commissar of Defense Colonel-General NN Voronov knew about the test results, nevertheless they signed the TTT data.
Along with the ZIS-3, the 57-mm IS-1 anti-tank gun was supposed to be used as an alternative weapon for the light assault self-propelled gun. It was a revised anti-tank gun ZIS-2, in the summer and autumn of 1942, this gun was developed by the design bureau of plant number 92 under the leadership of V. G. Grabin. The same gun was supposed to be used on the ZIS-41 semi-tracked self-propelled gun. According to the requirements, the ammunition load of the assault self-propelled gun, armed with the ZIS-3, was supposed to be 60 rounds. The combat weight of the vehicle did not exceed 10 tons, and the height in the stowed position was no more than 2 meters. The design maximum speed reached 45 km / h, and the cruising range was 200–250 km.
The design of the chassis was to be developed with the possibility of building an anti-aircraft self-propelled gun (ZSU) on the same base. At the same time, the TTT for the "37 mm self-propelled anti-aircraft gun" was issued separately. The layout of this machine almost completely repeated the SU-31, this also applies to the parallel arrangement of the GAZ-202 engines. Unlike the previous development, this time the T-70 was the base of the vehicle. The requirements for the characteristics of the chassis turned out to be similar to the TTT for the "76-mm assault self-propelled gun".
In addition to the 76-mm self-propelled guns and the 37-mm SPAAG, a third vehicle based on the T-70 appeared. On the same day (October 16, 1942) Voronov and Yakovlev approved the TTT for the "45-mm anti-tank self-propelled gun". As a weapon, it was supposed to use the 45-mm anti-tank gun M-42, which had recently been adopted by the Red Army. The T-70 tank was supposed to be used as a base, and in this case it was about the tank itself, and not about its chassis.
On October 19, 1942, Stalin signed GKO decree No. 2429 "On the production of prototypes of self-propelled artillery units." The ZSU was not included in the original text, it was included already in the course of the edits:
“2. To oblige the Narkomtankoprom (Comrade Zaltsman) and Narkomsredmash (Comrade Akopov) to immediately create samples of self-propelled artillery mounts with a 76 mm cannon based on the aggregates of the T-70 tank, submitting them for field tests by November 15 of this year. G.
3. To oblige the People's Commissariat for Sredmash (Comrade Akopov) to immediately create a model of a self-propelled artillery unit with a 45 mm cannon based on the T-70 tank, submitting it for field tests by November 20 of this year. G.
4. To oblige the People's Commissariat for Tank Industry (Comrade Zaltsman) and the People's Commissariat for Sredmash (Comrade Akopov) by December 1 of this year. G.to produce and submit for field tests samples of self-propelled artillery anti-aircraft guns with 37 mm cannons based on the aggregates of the T-70 tank."
All three SPGs were ordered by GAZ to develop them. Molotov. The 76-mm assault self-propelled gun received the factory index GAZ-71, the leading engineer of the vehicle was V. S. Soloviev. ZSU received the factory designation GAZ-72, A. S. Maklakov was appointed as the lead engineer. Finally, the 45 mm SPG based on the T-70 tank received the factory designation GAZ-73. On the part of the GAU spacecraft, the work was accompanied by Major PF Solomonov, who from the fall of 1941 closely supervised work on self-propelled artillery. According to the plans, work on the GAZ-71 was supposed to be completed by November 15, on the GAZ-73 by November 20, and on the GAZ-72 by December 1, 1942.
In KB GAZ them. Molotov's attitude to the received tactical and technical requirements was rather lazy, however, as in the design bureau of plant No. 38. First of all, this concerns the layout of self-propelled units. Suffice it to say that neither Kirov nor Gorky were even going to design cars using GAZ-203 engines. The decision is quite reasonable, since, as mentioned above, the SU-32 power plant in the form of a pair of these motors overheated during tests. It is not surprising that in such a situation it was decided to use parallel GAZ-202 engines.
In addition, the life of the GAZ-73 project turned out to be very short-lived. No design images of this vehicle have survived, but in general it was supposed to resemble the IS-10 self-propelled gun, which was developed in the design bureau of plant No. 92. GAZ quickly realized that such a concept was meaningless. The matter did not progress beyond the design work. It turned out that for the normal placement of the gun, it was necessary to raise the vehicle's height by 20 cm. The fighting compartment was still small, and the fire maneuverability and rate of fire turned out to be low. As of the end of November 1942, work on the GAZ-73 changed its course: now the car began to be designed on the basis of the GAZ-71 chassis. Instead of forced GAZ engines, it was supposed to use ZIS-16 engines. The last mentions of this machine are dated November 29, 1942, then the work was stopped.
Things were completely different with the GAZ-71, which was called SU-71 in correspondence. By November 15, 1942, as required by the GKO decree No. 2429, they did not have time to make it. But by November 28, the car was built, and she was preparing for factory tests. The ACS turned out to be very original: formally, the SU-71 was based on the T-70B chassis, but many changes were made to the original chassis design. The drive wheels, along with the final drives, were moved from the front of the hull to the stern. Sloths, respectively, migrated to the bow, at the same time losing rubber. In the stern, namely under the floor of the fighting compartment, on the right in the direction of travel, the gearboxes from the GAZ MM and the clutches migrated. Under the floor of the fighting compartment, on the left in the direction of travel, the fuel tanks also migrated.
Unlike the SU-31, the gearboxes were not spaced along the sides of the hull, but were installed close to each other, next to them were the clutches. The designers performed the blocking of the main clutches in such a way that they could be turned off separately, so that it was possible to move on one motor. The engines themselves remained in the bow of the SU-71, but they were placed close to each other, shifted to the right, and the driver's seat moved to the left side.
The hull of the SU-71 was no less original. Its frontal part was assembled not from three, but from two parts. In the lower frontal sheet there were hatches for access to the engine starting mechanisms, and in the upper one there were the driver's hatch and the hatch for the engine access. The installation of weapons was also different: from the ZIS-3, only the swinging part and the upper machine were used, which was installed with its pin in the socket on the frontal leaf of the cabin. A similar design was envisaged at the plant number 37, but was never implemented there. Thanks to this solution, the wheelhouse became even more spacious (compared to the SU-32). The recoil mechanisms of the gun were covered with a casing of a very complex shape.
The upper sides of the hull and deckhouse were made as a single unit and had an inclined arrangement. Thanks to this decision, the SU-71 had a more spacious fighting compartment. True, the floor level turned out to be noticeably higher due to the fact that fuel tanks and transmission elements were located under it. The fighting compartment was accessed through a large double-leaf hatch in the upper aft deckhouse. The radio station was located on the left in the direction of travel, while the commander's place and his periscope device were on the right. Ammunition was placed in a stowage under the cannon (15 shots) and in boxes on the sides of the fighting compartment (three boxes on the right and one on the left, their covers in the stowed position served as seats), eight more shots were attached to the inside of the rear wall of the wheelhouse. Due to the lack of wings on the SU-71, most of the entrenching tool was also placed in the fighting compartment.
Original but unreliable
The problems that emerged during the development of the GAZ-73 self-propelled unit were the first, but far from the last failure of the GAZ Design Bureau named after I. Molotov. As mentioned above, as of November 28, the SU-71 was preparing for factory tests. Meanwhile, the design bureau of plant number 38 by this time not only developed its own car, which received the SU-12 index, but also managed to build it, as well as conduct factory tests, which ended on November 27. By November 30, it was supposed to send her to the Gorokhovets artillery scientific testing experimental range (ANIOP) for field tests. In Gorky, the work was delayed, which is why the self-propelled unit was already overboard at the beginning of December. On December 2, 1942, GKO decree No. 2559 "On the organization of the production of self-propelled artillery installations at Uralmashzavod and plant No. 38" was issued. Even before the start of joint trials, the Gorky SPG was out of work.
Despite the decision of the State Defense Committee to produce the SU-12, the comparative tests of the SU-12 and SU-71 have not been canceled. The SU-12 arrived at the Gorokhovets ANIOP on December 5, by that time the SPG had covered 150 km during factory tests.
As for the SU-71, its delivery to the test site was delayed. On December 3, Major Solomonov, a member of the test commission, was sent to GAZ. In the course of the subsequent negotiations with the management of the plant, in which the chairman of the commission, Lieutenant-General of Artillery V. G. Tikhonov, also took part, the date for the SU-71's arrival at the range was set on December 6. The car did not arrive at the appointed time, and only after the second arrival of Tikhonov at the GAZ SU-71 was sent to the landfill. However, halfway through, the ACS was returned back due to a malfunction of the engine cooling system. As a result, the SU-71 reached the test site on December 9, only to return to the plant the next day after a program of factory tests and firing.
Again, the SU-71 entered field tests only on December 15. Together with her arrived the head of the OKB GAZ V. A. Dedkov and the military representative Kulikov. By that time, the SU-71 had managed to fire 64 shots and covered a total of 350 km. In the course of the ensuing field tests, full-fledged tests of the chassis were never carried out, since the car was constantly pursued by technical problems. As a result, the SU-71 underwent only full-fledged shooting tests, an additional 235 shots were fired to test the gun mounting system on the pin.
Even if we ignore the technical problems that constantly haunted the car, the SU-71 was far from going smoothly in terms of tactical and technical characteristics. Instead of 10 tons, as required in the TTT, the combat weight of the vehicle was 11, 75 tons. To a large extent, it was the significant overload that caused the engine overheating and a number of other malfunctions. The vehicle turned out to be 15 cm higher than it was supposed to, the vertical and horizontal aiming angles of its guns were insufficient. Due to technical problems, it was not possible to estimate the maximum speed, but there are serious suspicions that the car would not be able to accelerate to 45 km / h. One of its few positive features, the commission considered the design of the gun mount in the fighting compartment. In general, the verdict turned out to be quite expected: the self-propelled gun did not stand the tests, it could not be recommended for service, the revision was inappropriate.
Against the background of the failures that followed the GAZ-71 / SU-71, the GAZ-72 self-propelled anti-aircraft gun was lost. Moreover, its appearance is practically unknown. This happened because the work on the GAZ-72 dragged on even more. As of November 28, 1942, the vehicle body was not welded. According to optimistic forecasts of the plant management, it was expected to produce a prototype by December 6, but in reality the deadlines were delayed. In general, the car repeated the design of the GAZ-71. The difference was that a 37-mm 61-K anti-aircraft gun was installed in the stern. Structurally, the installation did not differ much from the one installed on the SU-31. To accommodate the installation, an extension had to be made in the aft section.
After the SU-71 was rejected, interest in the GAZ-72 also disappeared. Since these machines were built on a common chassis, it was obvious that similar problems awaited the car during sea trials. In addition, there were additional problems with the maintenance of the transmission. To gain access to its elements, it was required to remove the anti-aircraft gun. It is not surprising that work on the GAZ-72 did not progress beyond factory tests.
However, this is the development of light SPGs at the GAZ them. Molotov is not over. In May 1943, the GAZ-74 self-propelled gun was launched for testing, which is worthy of a separate story.
