The first Soviet self-propelled gun with a pronounced anti-tank orientation was the SU-85. This vehicle, built on the basis of the T-34 medium tank, was generally quite consistent with its purpose. But in the second half of the war, the SU-85's armor no longer provided the necessary protection, and the 85-mm gun could ensure confident penetration of the frontal armor of heavy German tanks at a distance of no more than 800 m. In this regard, the question arose of creating a self-propelled artillery unit capable of equal to resist all existing and promising enemy tanks.
The results of the shelling of captured German heavy tanks at the range showed that to significantly increase the armor penetration, it is necessary to increase the initial speed of an 85-mm caliber armor-piercing projectile to 1050 m / s or to use subcaliber projectiles with a carbide core. However, the creation of a new shot with an increased weight of the powder charge in wartime was considered impossible, and the mass production of sub-caliber projectiles required an increased consumption of scarce cobalt and tungsten. Tests have shown that for the confident defeat of heavy German tanks and self-propelled guns, a gun with a caliber of at least 100 mm was required. By that time, the 107-mm ZIS-6 tank gun (based on the M-60 divisional gun) had been created in the USSR. But the ZIS-6, like the M-60, had a separate-case loading, which limited the rate of fire. In addition, the production of the M-60 was stopped in 1941, and the tank version was never fully finalized. Therefore, for the new anti-tank self-propelled gun, it was decided to design a gun using unitary shots of the 100-mm universal naval gun B-34. The naval system originally had unitary loading, and the B-34 projectile had a higher muzzle velocity. The difference between the armor-piercing shells for the B-34 and M-60 was less than two kilograms. However, the creation of a tank 100-mm gun with acceptable weight and size characteristics was not an easy task. At the beginning of 1944, under the leadership of FF Petrov, a new 100-mm D-10S cannon was created on the basis of the D-10 naval anti-aircraft gun. The D-10S gun was lighter than its competitors and could be placed on the chassis of the T-34 medium tank without significant changes and unnecessary increase in the mass of the vehicle.
Self-propelled artillery unit SU-100
In February 1944, tests of the SU-100 self-propelled artillery unit began, during which 1,040 shots were fired and 864 km covered. When creating the SU-100, the designers of Uralmashzavod used the developments on the modernized SU-85, created at the end of 1943. The composition of the crew of the SU-100 has not changed compared to the SU-85, but many significant improvements have been made, of which the appearance of the commander's cupola was the most noticeable. However, when developing a new tank destroyer, the caliber of the gun was not only increased. To provide protection against the most common German 75 mm Pak 40 and Kw. K.40 L / 48 guns, the thickness of the upper front plate and the driver's hatch increased to 75 mm at an angle of inclination of 50 °. The thickness of the side armor remained the same - 45 mm. The thickness of the gun mask was 100 mm. The double-leaf panoramic hatch in the roof of the hull has changed a lot, and the MK-IV periscope has also appeared in its left wing. The observation periscopes along the perimeter of the wheelhouse were removed, but the exhaust fan returned to the roof. The tilt of the stern leaf of the felling was abandoned, which increased the volume of the fighting compartment. The general design of the gun mount was similar to the SU-85. Also, the left front fuel tank was removed from the fighting compartment, and the suspension of the front road wheels was strengthened. Ammunition in comparison with the SU-85 has decreased by almost a third, to 33 rounds. The gun was mounted in the frontal slab of the cabin in a cast frame on double pins, which allowed it to be guided in the vertical plane within the range from −3 to + 20 ° and in the horizontal plane ± 8 °. When firing direct fire, aiming at the target was carried out using a telescopic articulated sight TSh-19, and from closed positions using a Hertz panorama and a lateral level. During the tests, a rate of fire was obtained up to 8 rds / min. The practical rate of fire of the gun was 4-6 rds / min.
The SU-100 was equipped with a V-2-34 diesel engine with a power of 500 hp, thanks to which the ACS with a mass of 31.6 tons could reach speeds of up to 50 km / h on the highway. The speed on the march on a dirt road usually did not exceed 25 km / h. The capacity of the internal fuel tanks was 400 liters, which provided the car with a range of 310 km on the highway. Cruising in store for rough terrain - 140 km.
The standard for the serial SU-100 was the second prototype, on which the main shortcomings identified during the tests were eliminated. Instead of perforated track roller rims, solid rims with greater survivability were used. On the upper stern sheet of the hull, two smoke bombs were attached. Also on the roof of the wheelhouse, to the right of the panoramic hatch, a cap appeared, on which a new stopper of the gun was attached in a marching manner. The thickness of the armor of the commander's cupola was increased to 90 mm.
On July 3, 1944, GKO decree # 6131 was issued on the adoption of the SU-100 into service. The first batch of 40 vehicles was delivered to the military in September 1944.
During frontline tests, the self-propelled gun was highly appreciated, but deliveries to the combat self-propelled artillery regiments had to be postponed for several months due to the lack of mass production of 100-mm armor-piercing shells. By the way, the same problem was encountered during the combat use of BS-3 field guns. At first, their ammunition contained only unitary shots with high-explosive fragmentation grenades. Due to the forced delay in the production of the SU-100, a "transitional" unit, the SU-85M, went into production. This vehicle was produced from September to November 1944 and was a "hybrid" of the SU-100 chassis and the SU-85A armament.
Since the development in the production of the BR-412B armor-piercing projectile dragged on until October 1944, the first self-propelled guns entered training centers. Only in November were the regiments equipped with the SU-100 formed and sent to the front. The staffing table of the SAP was the same as that of the regiments that had the SU-85. The regiment consisted of 318 people and had 21 self-propelled guns (20 vehicles in 5 batteries and 1 self-propelled gun of the regiment commander). At the end of the year, on the basis of separate tank brigades, the first self-propelled artillery brigades (SABR) were formed: Leningrad 207, Dvinsk 208 and 209. The main reasons for the formation of the SABR were difficulties in managing and organizing the supply of the SAP, the number of which exceeded two hundred by the end of 1944. The brigade had 65 SU-100s and 3 SU-76Ms.
For the first time, the SU-100 was massively used in battle in January 1945 during the Budapest operation. Taking into account the fact that by the beginning of 1945 the Red Army was sufficiently saturated with anti-tank artillery, new T-34-85 and IS-2 tanks, as well as very effective anti-tank self-propelled guns SU-85, ISU-122 and ISU-152, the new SU-100 self-propelled guns did not have much influence on the course of hostilities. In addition, a number of design and manufacturing defects impeded the normal operation of the SU-100 at first. On some machines, cracks appeared in the welded seams of the hull and the destruction of parts of the gun mount during firing took place. Despite the fact that, based on the operating experience of the SU-122 and SU-85, the road wheels were strengthened and also made improvements in the suspension design, there was an increased wear of the first pair of road wheels. Not only the bandages were destroyed, but also cracks in the disks were found. As a result, it was necessary to simultaneously supply the units with new road rollers and develop a reinforced front road roller and a balancer to it.
The new self-propelled guns really showed themselves on January 11, when German tanks of up to 100 units, supported by infantry, launched a counterattack. On that day, 20 enemy tanks were burned by the forces of the 1453rd and 1821st SAP. At the same time, along with high anti-tank qualities, it was revealed that the SU-100 is more vulnerable to anti-tank infantry weapons than tanks. This was due to the fact that self-propelled guns initially did not have machine-gun armament, and aiming the gun at closely spaced targets required turning the hull. Due to the fact that the length of the D-10S gun barrel exceeded 5 meters, maneuvering in wooded areas and on city streets was difficult. In early January, the 382nd GvSAP, without even engaging in battle with enemy armored vehicles, lost half of the self-propelled guns as a result of an attack by enemy infantry, from which there was nothing to fend off.
In order to reduce losses from infantry armed with faust cartridges, some of the vehicles were additionally equipped with light machine guns. To destroy fortifications in settlements, it was decided to use ISU-152 and tanks.
The most massively SU-100 were used during the Balaton operation on March 6-16, 1945, when they repelled the counterattacks of the 6th SS Panzer Army. At the same time, the 207th, 208th and 209th self-propelled artillery brigades, as well as several separate self-propelled artillery regiments, were involved. During the operation, the SU-100 played a significant role in repelling German tank attacks and proved to be a highly effective means in the fight against German heavy armored vehicles, including heavy tanks PzKpfw VI Ausf. B Tiger II. As a result of the operation, the SU-100 were highly praised.
At the final stage of the war, German tanks rarely appeared on the battlefield, and the SU-100 crews mostly spent high-explosive fragmentation shells. However, in conditions when there was an opportunity to accurately aim the gun, the 100-mm high-explosive fragmentation projectile UOF-412 demonstrated good effectiveness against field fortifications, enemy manpower and lightly armored vehicles, significantly superior in high-explosive and fragmentation effect to the 85-mm UO-367 grenade … Cases were recorded when German medium tanks PzKpfw. IV were hit by 100-mm fragmentation grenades when firing at a distance of up to 4000 m. Apparently, we are talking about damage to the chassis with a close rupture of a powerful projectile weighing 15.6 kg, containing 1.46 kg of explosives. However, with a direct hit on the side, the relatively thin 30-mm side armor of the Quartet could also be pierced.
As for the armor penetration of the D-10S gun when firing the BR-412 armor-piercing tracer projectile, it turned out to be quite satisfactory. A projectile weighing 15, 88 kg had an initial speed of 897 m / s and at a distance of 1500 m pierced 115 mm armor along the normal. At a distance of 1000 m, when meeting at a right angle, a 100-mm projectile pierced a 135-mm armor plate. The shelling of captured tanks at the range showed that the 100-mm cannon penetrates the frontal armor of the Tiger and Panther at a distance of up to 1,500 meters. The side armor of the heaviest serial German tanks, which did not exceed 82 mm, as well as the frontal armor of the main mass medium tanks PzKpfw. IV and self-propelled guns StuG. III / IV, penetrated from a distance of 2000 meters or more. Thus, the armor penetration of the D-10S at real combat ranges allowed it to confidently hit the frontal armor of most German tanks and self-propelled guns.
Formally, protection from 100-mm armor-piercing shells at a distance of more than 500 m was provided by the frontal armor of the heavy tank PzKpfw VI Ausf. B. Tiger II, as well as heavy tank destroyers Panzerjäger Tiger Ausf. B and Sturmkanone mit 8, 8 cm StuK 43. But due to the acute shortage of alloying metals, the Germans in the second half of the war were forced to use high-hardness armor steel, and the armor of the Tiger-II tanks and the Jagdtigr self-propelled gun cracked and gave internal chips affecting the crew and equipment. Heavy tank destroyers "Ferdinand", due to the small number of built examples, did not have a significant impact on the course of hostilities, and if they appeared on the battlefield, they were destroyed by concentrated artillery fire.
The SU-100 self-propelled artillery mount appeared too late and could not fully demonstrate its high anti-tank potential on the fields of World War II. By April 1945, inclusive, the industry handed over 1139 self-propelled guns. But their use was largely constrained by manufacturing defects and problems with the chassis. In the spring of 1945, most of the "children's ailments" were cured, but the war in Europe soon ended.
Serial production of the SU-100 continued in the post-war period. In addition to Sverdlovsk, the SU-100 was produced in Omsk; by the beginning of 1948, a total of 3241 vehicles were built. In the post-war period, Czechoslovakia received a license for the SU-100, where another 770 self-propelled guns of this type were produced in the period from 1953 to 1956. ACS SU-100 were actively exported and participated in a number of local conflicts.
In our country, SU-100s were actively operated until the second half of the 1970s, after which they were in storage until the second half of the 1990s. The longest service of anti-tank self-propelled guns lasted in the Red Banner Far Eastern Military District. The vehicles built on the T-34 chassis demonstrated better cross-country ability on soft soils than the T-55 and T-62 tanks, which was important in a vast territory with numerous swampy river floodplains and taiga maria.
The SU-100 was also noted in the cinema. In the film "In War as in War", filmed in 1968 based on the story of the same name by Viktor Kurochkin, this self-propelled gun portrayed the SU-85, which in the late 1960s was no longer in good condition in the USSR.
Analysis of the anti-tank capabilities of Soviet self-propelled guns
In the final part of the cycle, devoted to the anti-tank capabilities of SPGs, let's try to find out which Soviet self-propelled gun was best suited for the role of a tank destroyer. As already mentioned in the previous publication dedicated to the SU-152 and ISU-152, these machines are most often called "St. John's wort". Another question: how fair is this?
It is clear that the hit of a 152-mm armor-piercing or even high-explosive fragmentation projectile usually ended fatally for any serial object of German armored vehicles. However, in practice, the dueling situation with the "Tiger" or "Panther" was conceived not in favor of the crew of the Soviet self-propelled gun. A heavy self-propelled gun armed with the ML-20S gun, which was a tank version of the 152-mm howitzer-gun mod. 1937, primarily intended for the destruction of long-term fortifications and fire support for tanks and infantry. With the powerful destructive action of the projectile, the "howitzer" origin made itself felt. The range of a direct shot at a target with a height of 3 m was 800 m, and separate-case loading in combat conditions did not allow more than 2 shots per minute to be fired.
The ISU-122, armed with the 122mm D-25S gun, had a much greater firing range compared to the ISU-152. This artillery system had a direct firing range at a target with a height of 3 m was 1200 m, and the effective firing range at armored vehicles was up to 2500 m. mm armor, which made it possible to confidently destroy enemy heavy tanks. Due to the deterioration in the quality of German armor at the final stage of the war, 122-mm shells demonstrated higher efficiency. There were cases when the "Panthers" failed after hitting the frontal projection at a distance of up to 2500 m. However, for a tank destroyer ACS ISU-122 did not have a high enough rate of fire - 1.5-2 rds / min. The problem of increasing the rate of fire was partly solved after installing the D-25S gun with a two-chamber muzzle brake on the modernized ISU-122S self-propelled gun. A more convenient location of the crew in the fighting compartment and the use of a semi-automatic gun shutter helped to increase the combat rate of fire to 3-4 rds / min, which, however, was still less than that of German tanks and tank destroyers armed with long-barreled 75-88-mm cannons.
In this regard, against the background of the ISU-122/152, the SU-100 looked more advantageous, the gun of which could fire up to 6 aimed shots. Although the 122-152-mm self-propelled guns had some advantage in terms of armor penetration, in practice, the effective range of destruction of heavy tanks of 1400-1500 m with an armor-piercing projectile fired from the D-10S was quite enough.
A fairly indicative criterion is the fire performance of Soviet 85-152-mm self-propelled guns used at the final stage of the war. The SU-85, armed with an 85-mm D-5S cannon, could fire up to 8 armor-piercing shells with a total weight of 76.3 kg at the enemy per minute. The SU-100, having fired 6 shots per minute, bombarded the enemy with 95, 28 kg of red-hot metal and explosives. The SU-122 could fire 2 armor-piercing shells with a total weight of 50 kg per minute. The ISU-122S, equipped with the faster-firing D-25S gun, fired up to 4 rounds per minute with a total weight of 100 kg. ISU-152, armed with an ML-20S howitzer, which gave an average rate of fire of 1.5 rds / min, when firing armor-piercing shells - 73, 2 kg. Thus, the SU-100 and ISU-122S are the champions in fire performance, while the SU-122 and ISU-152, armed with piston bolt guns, show the worst results. Against the background of 122-152-mm self-propelled guns, the SU-85 with a relatively low-power cannon looks very worthy.
It should also be borne in mind that the SU-100, created on the basis of the T-34, was much cheaper to manufacture than the heavy SPGs built on the chassis of the IS-85 tank. Formally, the protection of the ISU-122/152, covered in front with 60-90 mm armor, was higher than that of the SU-100, protected from the front by 75 mm armor. However, in reality, the difference in security was not so obvious. The slope of the 90-mm frontal armor of the ISU-122/152 was 30 °, and on the SU-100, the frontal armor was inclined at an angle of 50 °, which in terms of projectile resistance gave approximately the same 90 mm. Such armor at a distance of more than 500 m protected well against the Pzgr 39 armor-piercing shells fired from the 75-mm gun 7, 5 cm KwK 40 L / 48, which was installed on the modernized "fours". At the same time, the German 75-mm tank gun 7, 5 cm KwK 42, which was on the Panther, could penetrate the ISU-122/152 armor with an armor-piercing tracer projectile Pzgr 39/42 at a range of up to 1500 m. The rate of fire of the German 75-mm tank guns was 5-8 rounds / min. In the event of a direct collision with heavy German tanks at real battle distances, it was not protection that was of greater importance, but the rate of fire and mobility. The more maneuverable SU-100 was more difficult to get into, since it was 235 mm lower than the ISU-122, and the difference in height between the SU-100 and the ISU-152 was 625 mm.
It can be stated that the SU-100, well adapted for mass production, was the most optimal anti-tank self-propelled gun with a high rate of fire and decent armor penetration data with satisfactory protection and good mobility. At the same time, it can be concluded that the anti-tank capabilities of the D-10S gun during the war were not fully realized due to the lack of modern armor-piercing shells for it. Sharp-headed, carbide-tipped shells for Soviet tank and anti-tank guns were developed only in the post-war period.
It is a shame, but it should be admitted that our designers and industry in terms of creating a tank destroyer did not keep up with the needs of the army. This fully applies to SU-85, SU-100 and ISU-122S. By the summer of 1943, due to the increased security and firepower of German medium tanks and self-propelled guns created on their basis, the Red Army was in dire need of a self-propelled gun armed with an 85-mm anti-aircraft gun with ballistics. Taking into account the fact that the SU-85 was created on the basis of the SU-122, launched into mass production at the end of 1942, this machine could have appeared much earlier. It was the SU-85 that actually became the main Soviet tank destroyer, which destroyed many more German tanks than the more advanced self-propelled guns. By the time the SU-100 and ISU-122S appeared in the Red Army in noticeable quantities, the Panzerwaffe ridge was actually broken, and these machines did not have a significant impact on the course of the war.
