Soviet post-war 57-76 mm self-propelled artillery units
Soon after the end of World War II, the Soviet Union reconsidered the role and missions of the Airborne Troops. On June 10, 1946, the "winged infantry" was transferred to the Ground Forces, directly subordinated to the Minister of the Armed Forces of the USSR, after which the Airborne Forces began to be considered the reserve of the Supreme Commander-in-Chief.
Taking into account the specifics of the actions and tasks for the Airborne Forces, special equipment and weapons were required. In connection with this, from the second half of the 1940s, the development of air-transportable self-propelled artillery units was underway.
Experimental ASU-57 from OKB-115
Usually, armored vehicles are designed by teams with certain experience in this field. However, in the competition to create an air-transportable self-propelled gun in the second half of the 1940s, OKB-115, headed by aircraft designer A. S. Yakovlev, decided to participate. In 1948, his design bureau was developing the Yak-14 amphibious glider, and in parallel, it was planned to make a light self-propelled gun compatible with it, which, like the product designed by the Design Bureau of Plant No. 40, received the designation ASU-57 ("Airborne self-propelled gun of 57-mm caliber").
Although OKB-115 had no experience in creating such vehicles, the work proceeded at a rapid pace, and in March 1948, construction of a metal prototype began. There is information that assistance in creating the SPG was provided by specialists from the Kharkov Tank Repair Plant.
Specificity aviation The bureau left its mark on the design of the self-propelled gun. Although the front-mounted self-propelled gun outwardly resembled the "classics" of the Great Patriotic War: the SU-85 and SU-100, the new self-propelled gun for the Airborne Forces, designed by OKB-115, contained a number of revolutionary technical solutions for that time.
The welded hull of the self-propelled gun was made of armor sheets with a thickness of 4 to 12 mm. In the upper part of the semi-open cabin there was a folding commander's cupola of a streamlined shape with observation devices. In the stern part there was a carburetor engine M-20E with a capacity of 55 hp.
The length of the SPG, including the gun, was slightly more than 4500 mm. Width – 3820 mm, height – 1380 mm. Weight – 3255 kg. According to the design data, the vehicle was supposed to reach speeds of up to 45 km/h and have a cruising range on the highway of at least 160 km. The crew consisted of two people.
The angled frontal plate contained a niche for a 57-mm 113P automatic cannon, originally designed for future fighter aircraft. The gun mount was mounted with a rearward shift, due to which only a limited part of the barrel with a muzzle brake protruded through the embrasure. The barrel passed through the entire cabin, and the breech was located next to the engine compartment.
The gun was aimed in two planes using hydraulic drives. Horizontal aiming was possible in a 16° sector, vertical aiming angles were from -1 to +8°. The PBP-1A aircraft collimator sight was used for aiming.
The 113P cannon's automatic system operated by recoil with a short barrel stroke. The rate of fire was 135 rounds/min. It was fed from a disintegrating belt of 15 unitary rounds measuring 57x350 mm. The normal ammunition complement was 30 rounds. In case of overload, it was possible to take another 20 rounds with the placement of additional ammunition in a separate box. Reloading after the first belt was used up was carried out hydraulically. The next reloading required the participation of the crew.
In mid-1948, a prototype of the SPG arrived for testing at the Kubinka proving ground. Testing of the vehicle lasted several weeks, but the results were disappointing for the OKB-115 management. The chassis was not strong enough. Testers noted overheating and poor reliability of the engine, as well as its tendency to catch fire.
During firing, the aircraft 57-mm cannon, due to the use of low-power ammunition, quite predictably demonstrated weak armor penetration. The muzzle brake of the cannon, located close to the cabin, raised dust, interfering with observation, and also had a negative effect on the crew. The hydraulic guidance system worked unsatisfactorily, and during firing the pressure in it dropped. The speed of movement of the cannon and the sight did not match. The design of the guidance systems excluded the use of a traveling stopper for the cannon. The aircraft sight turned out to be ineffective at long distances. The ammunition supply system according to the project, providing for quick replacement of the belt by the gunner, in practice during reloading required the work of two gunners and took about 10-15 minutes. In this case, the crew had to leave the space protected by armor.
The tests failed and the self-propelled gun was returned to the manufacturer. However, OKB-115 attempted to modernize the self-propelled gun. In doing so, the semi-open habitable compartment was abandoned. A solid roof armor appeared behind the commander's cupola. The power plant remained the same, but all auxiliary units that had caused complaints during testing were redesigned. Hydraulic guidance was abandoned. artillery installations and it was guided by manual drives. The angle of inclination was reduced to -2° with the possibility of increasing to -5° by opening the hatches above the breech. The reloading system became pneumatic. The PBP-1A collimator sight was replaced by an OP-1 optical sight with 3x magnification and a field of view of 14°. The main armament remained the same, but it was decided to supplement it with a removable launcher for 30 RS-82 rockets. The launch was controlled from under the armor or from a remote control. The equipped RS-82 launcher added 320 kg to the mass.
At the end of October 1948, the redesigned SPG was sent to Kubinka for new tests, and it did not cause any particular complaints. However, by that time the military had already lost interest in the OKB-115 product, and soon the ASU-57, created by the Design Bureau of Plant No. 40, was adopted for service.
Experimental 57-mm floating self-propelled gun K-73
Under the leadership of A.K. Kravtsev, the Design Bureau of the Engineering Committee of the Ground Forces, in parallel with the K-75 APC, was designing the K-73 floating self-propelled artillery unit, which could be parachuted on a platform separately from the crew or landed by a Yak-14 glider.
The K-73 SAU had an open hull divided into three compartments. The MTO, separated by a partition from the habitable space, was located in the front part of the hull. The control compartment and the fighting compartment were located in the open rear part.
The front part of the hull and the cabin were assembled using rivets from 6-8 mm thick armor plates, the sides - 4 mm. The thickness of the duralumin bottom was 3 mm. To reduce the weight of the self-propelled gun, the rear vertical wall and fenders were also made of 1,5 mm duralumin. A wave-deflecting shield was installed in the forward part of the hull, which rotated and pressed against the hull during movement on land. All hatches of the machine were equipped with rubber gaskets for sealing.
The equipped weight of the vehicle was 3,4 tons. The length of the hull was 5355 mm. The length of the self-propelled gun with a gun was 5580 mm. The width was 2085 mm. The height was 1510 mm. The crew consisted of 3 people.
Experimental self-propelled gun K-73
The self-propelled gun was armed with a 57-mm Ch-51 cannon, installed in the cabin on a welded frame, with a slotted muzzle brake. The vertical guidance angles were from -4,5 to +15°. The horizontal firing sector was ±8°. The ammunition load was 30 rounds. The combat rate of fire was up to 9 rounds/min. The cannon was paired with a 7,62-mm SGMT machine gun with 400 rounds of ammunition.
The 70 hp power plant, borrowed from the GAZ-51N truck, provided a maximum speed of up to 54 km/h on land and 7 km/h afloat. Cruising range on the highway was 230 km.
When overcoming water obstacles, the air intake opening was sealed with flaps, and the air ducts were raised to prevent the ingress of seawater. In this case, air for cooling the engine and engine compartment was taken in by a fan from the fighting compartment. When overcoming water obstacles, a propeller was used, which was retracted into a special niche in the rear wall of the hull when moving on land.
In 1949, the Moscow Military Repair Plant No. 2 GBTU built two prototypes of the K-73 SAU. The first of them was intended for running tests (including afloat tests), the second - for artillery firing, which took place at the GNIAP GAU.
During firing, the artillery mount was found to be insufficiently durable. At the proving ground, the chassis and transmission demonstrated low reliability. Water tests showed that the hull was not airtight and that continuous rectilinear movement was impossible. Experts noted the possibility of lead splashes and bullets penetrating the hull through the gun, sight, and machine gun embrasures.
As a result, it was decided to transfer all design documentation and the prototype to the Design Bureau of Plant No. 40, headed by N.A. Astrov. There, the development of the floating modification of the ASU-1951 was underway since September 57.
One copy of the K-73 self-propelled gun was sent to the Militaryhistorical Museum of armored weapons and equipment (Kubinka village), where it is still on display.
Self-propelled artillery unit ASU-57
In 1949, testing began on the ASU-57 self-propelled gun (object 572), created under the supervision of N. A. Astrov and D. I. Sazonov in the design bureau of Mytishchi Plant No. 40.
In terms of layout, the ASU-57 resembled the ASU-76 created earlier there, but was lighter. The ASU-57 was in serial production from 1950 to 1962 at the Mytishchi Machine-Building Plant. During this time, more than 350 self-propelled guns were produced.
ACS-57
The design of the ASU-57 met the requirements of air mobility. The length of the SPG hull was 3480 mm (5750 mm with the gun), width - 2086 mm, height - 1460 mm. The vehicle had a layout with the engine and transmission compartment located in the front and the fighting compartment, combined with the control compartment, in the rear of the hull.
The hull was assembled from steel and duralumin sheets. The fighting compartment was open at the top. The frontal armor thickness was 6 mm, the sides - 4 mm. The upper part of the fighting compartment had 4-mm shields, attached to hinges, which could be folded back to reduce the height of the SPG and improve visibility. In this position, the crew was covered with armor at approximately shoulder level. On the march, the fighting compartment could be covered with a tarpaulin awning.
The use of thin armor plates made the self-propelled gun record-breakingly light. The vehicle's unladen weight was 3,35 tons. The rational armor slope angles contributed to the increase in bullet resistance in the frontal projection: the upper nose plate has a slope of 20° to the vertical, the frontal plates of the fighting compartment - 36°, the roof plates of the engine-transmission compartment - up to 65°. In addition, the side shields of the fighting compartment are located at an angle of 14°. The frontal 6-mm armor relatively reliably protected against rifle bullets fired from a distance of 400 m, and the sides - from light fragments.
It is worth admitting that the protection of the vehicle was very weak, which was to some extent compensated by its small size, good mobility and cross-country ability. In any case, the self-propelled anti-tank gun was better than a towed gun of the same caliber under equal conditions.
For self-defense against enemy infantry, in addition to personal weapons, the crew had at its disposal a SGMT machine gun, which was mounted on the front of the turret. However, later the relatively bulky and heavy machine gun was replaced by a RPD-44 light machine gun chambered for an intermediate cartridge.
The M-20E carburetor engine from the GAZ M-20 Pobeda passenger car with a power of 55 hp allowed acceleration on the highway to 45 km/h. The speed on rough terrain did not exceed 25 km/h. Cruising range on the highway is up to 250 km. Crew - 3 people.
The ASU-57 was armed with a 57-mm semi-automatic gun Ch-51 with a barrel length of 74,16 calibers / 4227 mm (length of the rifled part - 3244 mm). The gun was equipped with a muzzle brake. The gun's vertical guidance angles were from -5 ° to + 12 °, the horizontal firing sector was ± 8 °. The sight was designed to fire armor-piercing shells at a range of up to 2000 meters, fragmentation - up to 3400 meters. In terms of the ability to destroy enemy armored vehicles and manpower, the ASU-57 was on par with the 57-mm anti-tank gun ZIS-2.
After 1954, the self-propelled guns were armed with a modernized Ch-51M gun, which featured a more compact active muzzle brake, modified recoil devices, and a breech.
The 57-mm armor-piercing tracer projectile BR-271 weighing 3,19 kg, leaving the barrel with an initial velocity of 975 m/s, could penetrate 500 mm of armor at a range of 100 m at normal. The subcaliber projectile BR-271N weighing 2,4 kg, with an initial velocity of 1125 m/s, could penetrate 150 mm of armor at normal from half a kilometer. The ammunition also included rounds with a fragmentation grenade UO-271U weighing 3,75 kg, which contained 220 g of TNT. The practical rate of fire of the Ch-51 when firing with aiming correction was 8-10 rounds/min. Rapid fire - up to 15 rounds/min. Ammunition: 30 unitary rounds with armor-piercing and fragmentation shells, unified with the ZIS-2 anti-tank gun.
As of the mid-1950s, the ASU-57 could not only fight medium tanks, but also to destroy manpower and suppress enemy firing points. For lack of anything better, poorly protected self-propelled guns were also considered as an armored means of reinforcing the Airborne Forces in an offensive.
For a long period of time, the ASU-57 remained the only airborne armored vehicle capable of providing fire support to the landing force. Before the BMD-1 and BTR-D entered service, in cases where rapid personnel transfer was required, self-propelled guns could transport up to four paratroopers on their armor, as well as tow 57-85 mm cannons or 120 mm mortars.
Initially, only the Yak-57M transport and assault glider could be used to deliver the ASU-14 by air. Its design, compared to the early version of the Yak-14, was specially reinforced to transport armored vehicles weighing up to 3600 kg. Il-12D military transport aircraft were used as tugs for the assault gliders. The situation changed after the adoption of the An-8 and An-12 turboprop military transport aircraft, as well as the Mi-6 heavy transport helicopters.
The mass production of the An-12 and Mi-6 made the Airborne Forces a truly mobile branch of the armed forces. The ASU-57 was airdropped both by landing and parachute. Towards the end of its career, the ASU-57 was airdropped from heavy military transport An-22 and Il-76 aircraft.
The crew jumped with parachutes separately from the artillery mount and after landing released the equipment from the landing equipment. This scheme is not very convenient, since the scattering of paratroopers and cargo platforms on the terrain could reach several kilometers.
The newly built ASU-57 and the vehicles in service began to be equipped with night vision devices for the driver in the late 1950s. Since 1961, they were equipped with more advanced communication equipment in the form of a set of R-113 radio stations and R-120 TPUs. The latest series of SAUs received an additional fuel tank.
Initially, the ASU-57 was a divisional-level anti-tank weapon. Subsequently, as a result of the reorganization of the Airborne Forces and the adoption of the 85-mm ASU-85 self-propelled guns, the self-propelled guns armed with 57-mm guns were transferred from the divisional level to the regimental level.
In the second half of the 1960s, the frontal armor of new British and American tanks became invulnerable to 57-mm shells. Despite this, the Airborne Forces command was in no hurry to part with the ASU-57, and the service of light self-propelled guns, which had excellent cross-country ability on soft soils, continued until the early 1980s.
There is no information about the participation of the ASU-57 in combat operations. But it is reliably known that these machines were used during the introduction of Warsaw Pact troops into Czechoslovakia in 1968.
Based on the ASU-57, a very limited number of ASU-57KShM command and staff vehicles were produced, which, instead of an artillery gun and ammunition, housed radio stations, work stations for a signalman and two officers.
An amphibious modification known as the ASU-57P ("Object 574") appeared in 1952. This vehicle had a sealed hull and was slightly different in appearance from the basic version.
A folding wave-breaker shield was installed on the upper frontal plate. For movement on water, there was a propeller with power take-off from the gearbox.
The ASU-57P self-propelled gun successfully passed tests in 1955 and was recommended for adoption into service. However, the military decided that the amphibious self-propelled gun was not superior to the ASU-57 in terms of firepower and protection, and the Airborne Forces had enough vehicles, the serial production of which had already been established, and the construction of the ASU-57P was limited to five experimental models.
Experimental self-propelled artillery unit ASU-76
The experimental ASU-76 SPG appeared much earlier than the serial ASU-57. But within the framework of this cycle, dedicated to post-war domestic anti-tank self-propelled guns, the story goes in ascending order of caliber, in connection with which the story about the ASU-76 comes later.
In 1944, the Design Bureau of Plant No. 38 developed, on its own initiative, and the production facilities built three experimental lightweight OSU-76 self-propelled guns, on which the oscillating parts of the 76-mm ZIS-3 divisional guns were installed. In mid-1944, the OSU-76 underwent field tests, as a result of which a number of shortcomings in the design of the vehicles and armament were discovered. The commission's conclusion stated that in order to ensure the proper combat qualities of the OSU-76, it was necessary to use a new 76-mm gun with the ballistics of the ZIS-3, but with less recoil.
As part of this task, in the late autumn of 1946, the design bureau of Plant No. 40 began designing the ASU-76 installation (Object 570), and the prototype was ready in December 1947. Testing and fine-tuning, which lasted from 1948 to 1949, were completed successfully, after which the vehicle was recommended for adoption into service.
Experimental self-propelled gun ASU-76
The ASU-76 belonged to the class of semi-closed self-propelled guns with the fighting compartment located at the rear. To minimize the size of the vehicle and reduce weight, the fighting compartment was combined with the control compartment. The open-top hull of the vehicle was welded from rolled armor plates, which provided protection for the crew from small arms fire and shell fragments. The thickness of the frontal armor of the cabin was 8-13 mm, the front of the hull - 6-8 mm, the side - 6 mm, the stern - 4 mm, the bottom - 6 mm.
The liquid-cooled carburetor engine GAZ-51E with a power of 70 hp could accelerate the 5,8-ton vehicle to 45 km/h on the highway. The power reserve was up to 220 km. The crew consisted of three people.
The main armament was a 76 mm D-56S cannon with a 52-caliber barrel and a slotted muzzle brake that reduced recoil by 50%. The BR-354 armor-piercing projectile, weighing 6,5 kg and with an initial velocity of 655 m/s, could penetrate an 1000 mm thick vertical armor plate at a range of 80 m. The ammunition also included Br-354N subcaliber projectiles that could penetrate 1000 mm of armor at a range of 110 m. In terms of destructive power, the HE shell fired from the D-56S corresponded to the ZIS-3. The rate of fire was 10 rounds/min. The maximum elevation angle was +11°, declination - -5°. The OP2-66 sight and a panorama for firing from closed positions were used for direct fire. To combat infantry and shoot at air targets, an RP-46 machine gun was installed on the turret.
If the shortcomings revealed during testing were corrected, the ASU-76 could have become a viable vehicle, but this did not happen, and the self-propelled gun was not put into production. Some authors claim that the low armor penetration of the 76 mm D-56S cannon is to blame. However, they overlook the fact that the tank version of the D-56T was installed on the mass-produced PT-76 amphibious tank, which was used in our country until the mid-1990s. The introduction of new cumulative shells into the ammunition allowed us to partially solve the issue of armor penetration, and in terms of the power of high-explosive fragmentation shells, the ASU-76 was on par with the SU-76M and the divisional ZIS-3. During the first post-war decade, the Airborne Forces did not have self-propelled guns with comparable characteristics of the HE shells. The refusal to produce the ASU-76 in series is most likely due to the fact that the Yak-14 airborne glider designed for the Airborne Forces could not carry a machine weighing 5,8 tons, and the heavy Il-32 glider with a carrying capacity of 7 tons was built in a single copy.
To be continued ...
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