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A Second Life for Obsolete Chassis

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Instances where obsolete tank chassis are used to make quite modern vehicles that nevertheless remained experimental are common. Nearly a dozen German SPGs were produced in tiny amounts but still saw front line service. One common example is the Pz.Sfl.V tank destroyer, better known as the Sturer Emil. This vehicle was built on the chassis of the VK 30.01(H) heavy tank that was never put into mass production. Only two Pz.Sfl.V were built, but they were used quite successfully.

This German SPG was brought up as an example intentionally. Today it is displayed alongside its Soviet analogues, which also remained experimental. These are the SU-14-1 and T-100Y SPGs, built as bunker busters. They did not make it to the Winter War, but were likely used in battle during the defense of the NIBT Proving Grounds. Both vehicles were built on the chassis of tanks that were either considered obsolete or otherwise unfit.

A matter of grave importance

The Winter War began on November 30th, 1939. Unlike the fighting at Khalkin-Gol, where the two sides fought on equal footing, the Red Army had a numerical advantage. However, it was not that simple. The Winter War was an exceptional scenario where the Red Army had to fight through the deep line of fortifications known as the Mannerheim Line in winter.

Pillboxes built in 1938-39 posed the biggest issue. A number of them were nicknamed "millionaires", hinting at how expensive they were to construct. This investment paid off in the first month of the Winter War. Due to poor reconnaissance, these modernized fortifications were a surprise for the Red Army. As a result, the December offensive on the Mannerheim Line failed.

The Mannerheim Line was an unpleasant surprise for the Red Army.

The North-Western Front under the command of Army Commander 1st Class S.K. Timoshenko was formed on January 7th, 1940. His new appointment was followed by a flurry of preparations for assaulting the Finnish defenses, including the thickly-walled pillboxes. It turned out that the 152 mm Br-2 special power gun was the best weapon against them. The semi-AP naval shell penetrated a 130 mm plate with a 40 mm thick iron lining at 30 degrees at a range of 5000 meters. The shell shattered after the fact, and so orders were given to develop a more robust shell. Calculations showed that the same shell could penetrate up to 2 meters of reinforced concrete, making it a potent weapon against Finnish fortifications.

The 152 mm model 1935 special power gun turned out to be the best weapon against Finnish fortifications.

Work went in a different direction, however. The Red Army accepted the KV heavy tank into service on December 19th, 1939. The U-0 prototype went into battle the day before. A letter arrived at the Kirov factory on January 11th, 1940, ordering the development of a KV tank with a 152 mm M-10 howitzer. Order #1ss to authorize this work was signed on January 14th. The factory indexed this gun mount MT (later MT-1). Production of 4 such vehicles was expected in January. These four tanks (the converted U-0 and U-1 through U-3) took part in the war. It turned out that their howitzers were not powerful enough to break through the walls of pillboxes, but they could be used to destroy other fortifications, including Dragon's Teeth. While these tanks, later accepted into service as the KV-2, fought with Finnish fortifications, factory #185 was busy working on proper bunker busters.

A second chance for the SU-14

The biggest issue with the KV chassis was that it could not fit a more powerful weapon than the M-10 howitzer. There were alternatives that theoretically could fit a larger gun. Two such vehicles were already on hand: the SU-14 prototype SPGs.

The SU-14 in its initial state.

The issue of mechanizing artillery in the Red Army was raised in the early 1930s. The first issue was the mechanization of divisional artillery, as existing tank chassis did not allow for anything larger. The situation began to change towards the end of 1932 when the T-28 and T-35 tanks were accepted into service. Both tanks were developed by factory #174's OKMO design bureau (led by N.V. Barykov with S.A. Ginzburg as the lead engineer). Both could carry heavy artillery systems. The first attempt was the SU-7 "large triplex". Tactical-technical requirements were composed on March 3rd, 1933. They called for a 254 mm gun, 305 mm howitzer, or 400 mm mortar on the T-35 chassis.

Neither the SU-7 nor weapons for it were ever built. Another vehicle arrived closer to June of 1933. This SPG, designed for the 203 mm B-4 special power howitzer, was indexed SU-14. The SU-14 was a higher priority project. The B-4 had just been accepted into service in 1933, so an SPG with it would be quite timely. The T-28 was chosen as the chassis, but it was different from its ancestor from the very beginning. The lead engineer on this project was P.N. Syachintov. L.S. Troyanov, a future famous heavy SPG designer, also put a lot of work into this project.

SU-14 after improvements and installation of a 152 mm B-30 naval gun.

The SU-14 became a duplex by 1934. In addition to the B-4, the vehicle would also have the option to carry a 152 mm B-10 special power gun. By that point, the OKMO was split out into factory #185. The prototype was built in July of 1934, ahead of schedule, and the first trials took place in August. Gunnery trials were conducted successfully, but mobility trials ended in embarrassment. The use of T-28 components on such a heavy vehicle was a mistake, and so the question of using T-35 components was raised. This also applied to the tracks, since the ground pressure was immense. 8 changes in total were requested for the running gear, the same number for the transmission, and 10 changes in equipment. It turned out that the SU-14 could only be partially converted to use T-35 components. A decision to build an SPG using T-35A components from the start was made at a meeting held on October 30th, 1934. This vehicle was indexed SU-14-1.

SU-14-1 on trials, summer 1936.

Even though the SU-14-1 pilot only entered trials in 1936, the vehicle was accepted into service on June 10th, 1935. This decision was made as a result of trials of the converted SU-14. The creators of the SU-14 were heavily rewarded (for instance, Syachintov received an 8000 ruble bonus) and it was assumed that the first 10 vehicles of this type would be built in 1935 at HPZ. As for the first prototype, a decision was made to install a superior weapon: the B-30. This gun was installed in 1937 and gunnery trials were conducted in September of that year. Work on the SU-10, a variant of the SU-14 for coastal defense, began in 1936. Meanwhile, trials of the SU-14-1 were not quite so smooth. 167 various defects were discovered. No conclusions were made. The ABTU ordered that the pilot vehicle should be corrected in November of 1936.

Trials of the pilot revealed a number of issues. Largely, the vehicle was dead in December of 1936. A rate of fire of 1 shot every 5-7 minutes was far from what was expected.

Some authors write that the SU-14 was not put into production because Syachintov was executed, others because HPZ was overloaded. However, archive documents tell a different story. The Scientific-Technical Department of the Red Army's Artillery Directorate clearly wrote in late 1936 that the SU-14-1 could not be accepted for military trials, let alone mass production. The rate of fire was only one shot per 5-7 minutes and there were issues with the gun.

Factory #185 continued working on the SU-10. Work was led by I.S. Bushnev. A.P. Masalakin was responsible for experimental production. He also worked on the SU-14-1. In practice, work on the SU-14 had stalled by the end of 1936, including preparations for mass production. Syachintov was arrested on December 31st, 1936, due to the large amount of his projects that were accepted into service but could not be mass produced. No doubt, the SU-14 was one of the reasons why he was arrested and then executed. Formally, the SU-14 was cancelled on August 7th, 1938, but in practice it was dead long before that.

The re-invented SU-14, summer of 1940.

The SU-14s remained at the Artillery Directorate's Scientific Research Artillery Proving Grounds. These vehicles found a second life with Committee of Defense decree titled "On special tasks for needs of the Active Army" issued on January 17th, 1940. The decree ordered factory #185 to equip the two SU-14s with full armour and the 152 mm Br-2 gun. The requirements slightly changed. The SU-14 already had the B-30 gun with serial number 2, which was close to the Br-2 in its characteristics. Inspection showed that it was in good condition, so there was no need to change it. As a result, factory #185 received only one Br-2 gun (serial number 4) on February 8th, 1940.

The SU-14-1. As one can see, the vehicles are slightly different.

Work on the SU-14 bunker buster proceeded quickly. Barykov was in charge of the overall project jointly with F.A. Mostovoy. A.P. Masalakin was effectively the lead engineer. This was a logical decision, considering that he knew the vehicle well. Since the SU-14 and SU-14-1 chassis were somewhat different, the conversions were also different. Nevertheless, the overall concept was the same. Since the vehicles would fire directly from a range of 1500-2000 m, the front armour was increased to 50 mm. Some areas used monolithic plates, some had applique armour. The sides were 30 mm thick (60 mm in the front section) and the rear was 20 mm thick. Such an impressive amount of armour increased the weight of the vehicles to 64 tons and the ground pressure to 0.946 kg/cm². Both vehicles used the 500 hp M-17L engine. The estimated top speed was 22-25 kph on a highway and 6-10 kph off-road.

The vehicle had a closed fighting compartment. The bulges in the rear house the deployable trails.

The fully armoured casemate had its drawbacks. The towed Br-2 had a maximum elevation angle of 60 degrees. The SU-14s were limited to 31 degrees. This was more than enough, considering that the vehicle's job was to fight bunkers. The gun received a new travel lock, which was different on both vehicles. PT-1 and PTK-1 periscopes as well as the KT-1 prismatic telescope (the same one used in the DOT-4 fortress gun mount) were added. All 6 of the gun crew were located inside the casemate. The casemate was not the only change that was made. The fighting compartment was rearranged, making room for 28 rounds of ammunition. 4 DT machine guns were carried with 5 mounts for them plus one P-40 mount on the roof. The SU-14's fighting compartment was quite roomy. The same could not be said for the driver. He sat in a small box and it was now even harder to get to his station. Electrical equipment was all changed: the 71-TK-3 radio set and TPU-2 intercom were installed.

Even though factory #185 worked quickly, they did not meet their deadline. The fault lay with their subcontractor, the Izhora factory. Armour plates arrived from there only on February 23rd, and the first vehicle was shipped on March 13th, the day the Winter War ended. This was not the only vehicle at factory #185 that was late to the war.

A naval alternative

The SU-14 was not the only chassis that could carry a gun similar to the Br-2 in performance. The story of a potential replacement for the T-28 and T-35 was coming to an end around this time. The history of this tank began in April of 1938. Requirements for the vehicle named "vehicle 100" (later T-100) at factory #185 were composed by April 26th. The requirements called for a 55-60 ton vehicle with one 76 mm L-10 gun and three 45 mm guns. The crew numbered 11 men. The tank would have an 850 hp GAM-34 engine and carry 60 mm of armour all around. These requirements only reflected factory #185's vision. On April 28th it turned out that there would be a tender. Kirov factory's SKB-2 presented their own tank called SMK-1. This was the start of a battle between two design bureaus: factory #185 and Kirov factory's SKB-2, which was taken over by Zh.Ya. Kotin a year prior. Some name S.A. Ginzburg as an author of this vehicle, but that is not the case. An order issued on June 20th, 1938, named I.S. Paley as the lead engineer on the project. The running gear was developed by Maksakov and the armament by G.N. Moskvin. Ginzburg was no longer working at factory #185 at the time.

T-100 breakthrough tank prototype. This was factory #185's attempt to create a replacement for the T-28 and T-35.

The T-100 changed several times during development, taking its final form towards the start of 1939. The armour and engine remained the same, but the number of guns and turrets was reduced to two. The tank weighed 58 tons, 3 tons more than the SMK-1. The experimental T-100 was finished on July 1st, 1939. It was already falling behind in the breakthrough tank tender. The average speed turned out to be lower than its competitor's, and the top speed was only 32 kph instead of the planned 35.7. Meanwhile, the SMK's top speed was 38 kph.

The cruising range was also lower. The GAM-34 had a low lifespan. There were issues with the cooling system. The suspension turned out to be too complicated and the road wheels were insufficiently robust. The SMK-1 was not the favourite by then either. The new KV tank entered trials on September 1st, 1939. The KV tank was "half" of the SMK-1. At a mass of 40 tons, it had the same armament and 75 mm of armour. Factory trials clearly showed that the vehicle was a higher priority. Factory #185 wanted to build its own "half", but the 050 tank remained on paper. The T-100 was still worked on by December of 1939, for example it was equipped with a torsion bar suspension. Work was also underway on the 1000 hp MN-1 engine. The fate of the second prototype that was originally due in early January of 1940 changed radically by the end of the month.

Production of 130 mm B-13 and 100 mm BS-3 guns at the Bolshevik factory, 1944. The B-13 was a common gun, unlike the Br-2, only 39 of which were built.

Factory #185 must have known something even before Timoshenko launched the program for countermeasures against Finnish fortifications. There is no other way to explain a letter that arrived from Barykov at the Bolshevik factory in which he asks for characteristics of the 130 mm B-13 gun. This naval gun was put into production in May of 1935. The B-13's characteristics were short of those of the Br-2, but not by much. It also had a number of advantages. For one, the gun had a mechanical rammer, which increased the rate of fire to 7-8 RPM. The mass of the shell was much lesser (33.5 kg vs 49 kg), but the penetration was almost the same. The model 1928 semi-AP shell penetrated the aforementioned armour at a range of 4400 meters. This gun, as well as factory #185's chassis, were both competitive alternatives. While it was impossible to install a Br-2 gun on the T-100, the smaller weapon was viable.

The SPG on the T-100 chassis could look like this. The T-103 "coastal defense tank" was a second attempt to put the 130 mm gun on the T-100 chassis.

Factory #185's design bureau began working on three vehicles (and later a fourth one). Two of them (X and Y) had fixed casemates. The third (Z) had a full turret. The T-100Z later turned into another vehicle armed with a 152 mm M-10 howitzer. The turret was built, but the request to put it on the first T-100 prototype was denied. The T-100X and T-100Y were no less interesting. On January 7th, 1940, the ABTU ordered factory #185 to build an engineering vehicle using the second T-100 prototype chassis. Factory #185 clearly had other ideas. A decision about which tank would be built had to be made. Y was chosen over X. This project was led by I.V. Gavalov. Mostovoy and Bushnev supervised all the projects.

As for the T-100Z, it lived on in a different form. "Special tank 103" also known as the T-103 was presented on March 28th, 1940. Looks like factory #185 decided to market their T-100Z to the Navy. The mass was reduced from 68 to 63 tons. The ammunition capacity remained at the same level: 50 shots. The coastal defense tank project was led by engineer-designer Shufrin, although the project did not progress past a model.

Cutaway of the T-100Y.

The T-100Y was in a different situation. The engineering tank was due on January 15th, but factory #185 had its own plans. They didn't even think about building the engineering tank. Blueprints for the T-100Y were sent to the Izhora factory on January 10th, 1940, but factory #185 cancelled the order on January 16th and offered to build the T-100Z turret instead. As a result of all these changes, the Izhora factory only received the blueprints for the T-100Y casemate on January 23rd. Interestingly enough, the ABTU was still certain that factory #185 was working on an engineering tank. Contract #8-8-087 for this vehicle was signed on January 21st, 1940. On January 25th, Barykov sent a letter to the Military Council of the North-Western Front with a proposal for his 130 mm SPG.

The factory got lucky. Timoshenko liked the idea of a cannon as the best weapon against Dragon's Teeth. On January 28th, 1940, he signed Military Council of the North-Western Front decree #20 "On transferring orders for production and installation to industry factories". A "tank with a B-13 gun" was listed as item #6. Meanwhile, the ABTU did not know about this plot twist (or pretended like they didn't know). One can only marvel at Barykov's courageous attempts to save the T-100. The kaleidoscope of orders had its impact. The Izhora factory complained about constantly changing orders and only delivered the T-100Y hull by February 22nd. The vehicle was finished on March 14th, a day after the war ended. Factory #185 had no one to blame but itself.

Experimental T-100Y.

The idea of the T-100Y as to quickly build an SPG with minimal changes to the base chassis. The turrets and turret platforms were removed. Instead, a B-13 gun was installed on a pedestal mount with minimal changes. The casemate was installed around the gun. The ammunition capacity was only 30 shots, a portion of which were stowed under the floor. The gunners sat above them. The gun crew consisted of four men: two gunners (one of which was also the commander), loader, and breech operator. The rammer made it harder for the loader to work. There was no telescopic sight. The gun was aimed using the PT-1 and PTK periscopes.

The fighting compartment was rather cramped.

The mass of the vehicle is different in different sources: some documents give the mass as 58 tons, others as 64, some as 68. The truth is likely somewhere in the middle. Despite the increased mass, mobility remained at the level of the T-100. The T-100Y was no doubt a more successful vehicle than the SU-14. Unfortunately, factory #185 was too late. The ABTU refused to pay for the T-100Y, stating that they ordered an engineering vehicle and got an SPG instead. Barykov and the ABTU continued to bicker for several months. The two sides were on equal footing. Correspondence shows that military engineer P.K. Voroshilov, the adopted son of the People's Commissar of Defense, was in charge of the project, and it was his idea to put the 130 mm gun into it. The story of this project is murky at best.

Vehicles without a future on a promising mission

Even though the SU-14 and T-100Y did not make it in time for the Winter War, bunker busters remained an important topic. Even though Finnish fortifications fell to other methods, a bunker buster was still needed. Nevertheless, with the end of the war the speed at which decisions were made was reduced. The issue of testing these vehicles was raised in April of 1940. Factory #185 obtained gunnery tables for the B-13 gun, but there was a complication. The B-13 could have several types of liners, which made its use more complicated. Factory #185 also obtained gunnery tables for the Br-2 and B-30 guns in mid-March.

In practice, trials only began at the Gorohovets artillery proving grounds on June 15th, 1940. All three vehicles were sent there. The SU-14-1 was criticized for its tightly opening breech. The gun mantlet impeded turning the gun, as it pressed up against the exhaust pipes and transmission access hatch hinges. There were also issues with synchronization of the periscopic sight. It was impossible to aim the machine guns. There were complaints about the straps used to move ammunition as well as the fume extractor system. There were also positive results. The SU-14-1 was a stable gunnery platform and there was no need to deploy the trails. The crew positions were set up quite well, and the casemate was well designed. There were only 8 items found that required changes. The SU-14 performed roughly the same. Both vehicles fired 5 shots. The report said that the real maximum gun depression was 15 degrees, not the 31 claimed in the description.

Proposed changes in the tank armament system, June 11th, 1940.

The T-100Y fired 6 shots. There were also complaints about the gun mantlet, but different ones. The mantlet was installed with no regard for balance, which made aiming difficult. The main complaint was the cramped fighting compartment. Footholds for the crew were recommended. The ammunition rack had to be changed, since its design was irrational. The shells were to be kept on the right side of the casemate and the propellant to the left. All vehicles were sent to factory #174 for correction of these defects. Factory #185 no longer existed, it was reabsorbed into factory #174. Here is where Ginzburg makes his return, as he was the chief designer at the factory's design department #20. The vehicles did not make it back to Gorohovets. They were used in July along with the KV-2 to fire at former Polish fortifications in the Kiev Special Military District. These trials showed issues with the running gear, especially on the SU-14. The trials ended. The vehicles returned to factory #174 in July of 1940 and then to the NIBT Proving Grounds near Kubinka towards September. The vehicles were heavily used by then, especially when it came to the running gear.

SU-14-1 at the NIBT Proving Grounds.

The T-100Y lost its last chance at mass production in June of 1940. It could be launched as a temporary measure, but the GABTU was leaning towards the SMK as it shared components with the KV-1. An SPG with two guns was planned on the chassis: either the Br-2 or the 180 mm B-1 naval gun. None of these ideas were put into practice. Decree #1288-495ss of the Council of People's Commissars and Central Committee of the VKP(b) was published on July 17th, 1940. This was the starting point for the 212 SPG. This was the spiritual successor to the SU-14 using KV-1 components. The T-100 and SMK were no longer in demand. The prototypes continued to rust away at the NIBT Proving Grounds, and factory #174 issued them a bill for 125,000 rubles for repairs. The proving grounds would have been happy to get rid of these "gifts", but this never happened. All three vehicles remained there until the start of the Great Patriotic War.

Condition of the SU-14 and T-100Y, 1942.

There is a commonly accepted theory that the vehicles that remained at the proving grounds by the fall of 1941 took part in its defense. This information is not confirmed, furthermore documents show that the vehicles were shipped to Kazan in the fall of 1941 where they were used as specimens in technical courses. They returned to Kubinka in 1943 alongside the TK-S tankette, VCL M1931 amphibious tank, Renault FT, and the BA-27M, BA-21, and PB-4 armoured cars. By 1945 the T-100Y was called SU-100Y. This index remained in use in post-war literature. The SU-14 was scrapped in the 1960s, but the SU-14-1 survived. It is sometimes called SU-14-2 or SU-14-BR-2, neither of which is correct. The SU-14-1 and T-100Y were put on display at the proving grounds. This collection later turned into a museum. The SPGs were moved to display area #1 at Patriot Park after it opened. The vehicles were also repainted.

This is how these vehicles look today.

Despite the fact that the SU-14 and T-100Y were not very successful, it is hard to call them complete failures. They were the first Soviet assault guns, and not the worst ones at that. The Red Army's bunker busters transformed into the SU-152, accepted into service on February 14th, 1943.

Unlike Gavalov, the SU-14 bunker buster was the last vehicle that Masalkin was involved with as the lead engineer.

To wrap up, let us discuss the fate of the vehicles' developers. I.V. Gavalov ended up in Gorky in October of 1941 where he worked under N.A. Astrov. He built several experimental vehicles there, including the GAZ-75. Fortune smiled upon him when he moved to VTZ and developed the BMD-1 airborne vehicle. Masalkin had a different fate. Like many other designers, A.P. Masalkin was mobilized into the army in August of 1941. He started out as the deputy technical commander of the 86th Independent Tank Battalion on the Leningrad Front, then continued to serve as the assistant chief of the Gorky vehicle center. He was stationed significantly north of Gorky, in Murmansk. Instead of developing new tanks, he was involved with acceptance of Lend Lease vehicles. He finished the war in the rank of Engineer-Colonel.

Original article by Yuri Pasholok.


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