Roots of the SU-152

"Approved: Deputy People's Commissar of Tank Production, Major General of the Technical Forces, Kotin

Approved: Chief of the GABTU BTU, Major General of the Tank Forces, Korobkov

January 31st, 1942

Tactical-technical requirements for a self propelled 152 mm howitzer on the KV-7 chassis

The 152 mm self propelled howitzer is similar in design to the KV-7 tank and is designed to be used for destruction of fortifications at close range

U-18 Controversy

After the conclusion of the Great Patriotic War, People's Commissar of Tank Production Malyshev ordered each factory to write up a record of their activity during the war. This is what UZTM wrote about their attempt to convert the strange looking KV-7 into a functional SPG.

"U-18

This is a project of a KV-7 SPG with the powerful 152 mm ML-20 gun.

The gun is also installed using a frame mount. The aiming angles are +15 to -5 vertically, 7 degrees 30 minutes to each side horizontally, or 15 degrees in total. The gun has good ballistic performance (43-51 kg shells, 550-650 m/s muzzle velocity) which gives 98 mm of penetration from 1000 meters compared to 49 mm from the ZIS-5 gun.

The explosive charge of the 152 mm shell is three times greater than that of the 76 mm shell.

On the Way to the SU-122

"To factory #8 director comrade Fratkin

CC: Chairman of the NKV Technical Council, regional GAU KA engineer at factory #8, Engineer-Colonel Kascheev

RE: development of self propelled howitzers.

Regarding the issue of designing a 122 mm self propelled M-30 or U-11 howitzer on the T-34 chassis, in accordance with the NKTP, I report that:

1. The turret platform of the T-34 tank can be extended to span the length of the hull, and the sloped sides can be placed vertically.
2. The fuel tanks can be located in the engine compartment. As a last resort, the shape of the fuel tanks can be changed
3. It is not permitted to change the hull of the T-34 tank or  the layout of the engine and transmission.

ZIK-20: Assault Alternative

On April 15th, 1942, the plenary assembly of the Artillery Committee of the GAU met to discuss further development of self propelled artillery. The decisions worked out in this meeting became key in wartime development of Soviet SPGs. Among others, requirements were confirmed for a heavy SPG that would replace the 212 bunker buster. Work began on this SPG on the KV-7 chassis at UZTM, headed by L.I. Gorlitskiy. By the fall of 1942, the U-18 project was ready, but by that point, a competitor was developed at Sverdlovsk.

KV-7: Lock, Stock, and Three Smoking Barrels

Work on heavy SPGs in the Soviet Union began in the early 1930s. By the end of the decade, development stopped, but began anew in early 1940. The Red Army needed tanks to destroy enemy pillboxes. The result of this requirement was the 212 SPG which, for various reasons, was never built. In April of 1942, the 212 project was finally closed, giving way to another no less interesting project: the KV-7 assault tank.

From the Top

November of 1941 was a difficult time for the Soviet Union. The Germans were pushing to Moscow, only tens of kilometers away. Battles were fought on the approach to Tula. Rostov-on-the-Don was lost. Factories evacuated to the east were just beginning to produce tanks. The Chelyanbinsk Tractor Factory, renamed ChKZ (Chelabinsk Kirov Factory), became the only factory to produce heavy KV tanks. Tankograd first managed to ship over 100 tanks this month, as its numbers were boosted by workers and engineers evacuated from Leningrad.

In these difficult times, a project of a quite unusual vehicle with hardly any analogues in tank building worldwide appeared. The first mention of this tank on the KV-1 chassis is made in P.F. Solomonov's report about his trip to Chelyabinsk, dated November 28th, 1941. The goal of this trip, initiated by GAU, was the investigation of the issue of gun supplies for the KV-1 tanks. Aside from supply issues, the report had room for experimental works, which included the following:

"On Iosif Vissarionovich Stalin's orders, the Kirov factory is developing a mount for a KV tank with 1 F-34 gun and 2 45 mm guns (barrels without recoil mechanisms), with recoil mechanisms for the triplex taken from the ZiS-5. There is no 360 degree traverse, the traverse is +/- 7.5 degrees or +/- 15 degrees, depends on how the ammunition racks are placed. Ammunition capacity: 300 rounds (100 per gun), in addition to which there are 3-4 machineguns.

In December, 1/5 KV tanks are to be equipped with these triplexes."

It could be imagined that the factory namedropped Stalin as a cover, but this is not the case. The fact that Stalin was the initiator of this project is mentioned in many documents. In addition, the GKO decree that relates to the KV-7 is written in Stalin's trademark pencil.

The KV-7 appeared because of many complaints from the front asking for improving the power of tank weapons against unarmoured targets, including light field fortifications. In theory, the triplex could fire each gun individually, or all three in a volley. The KV-7 was not the only project of this type. At the same time, in November-December 1941, a similar project was designed by factory #183, evacuated to Nizhniy Tagil. The tank, indexed T-34-3, was developed under A.A. Morozov. It consisted of a T-34 whose turret also had two 45 mm guns in addition to the F-34. The crew increased to 5 men, and the commander was freed from gunner duties. There is no information on who was the initiator of this project, but it's possible that it was the same person that ordered the KV-7. The T-34-3 technical project and design documentation were completed, but a prototype was never built.

T-34-3, an attempt to make a medium "volley" tank with a rotating turret.

The situation with the KV-7 was different, and the project was very different from what was proposed at Nizhniy Tagil. As with the "bunker buster" from the Urals, work was split between ChKZ and UZTM. SKB-2 in Chelyabinsk designed the chassis, supervised by G.N. Moskvin. OKB-3 at UZTM designed the weapons. Work on the gun system, developed by engineers N.N. Efimov and K.N. Ilyin began in November of 1941 and finished on December 10th. F.F. Petrov was the chief designer of this system, indexed U-13. A significant part was played by L.I. Gorlitskiy, who arrived from Leningrad and became the chief of the artillery design bureau at the Kirov factory.

U-13 gun system used on the KV-7.

Unlike the T-34-3, the KV-7 had no turret, as it was decided that the U-13 took up too much space. The turret and fighting compartment ceiling were replaced with a casemate. However, the word "casemate" was never used by the designers, who preferred the term "immobile turret". The casemate took a prismatic shape to improve crew conditions, the lower part of it spreading out to completely cover the fenders. As many parts from the KV-1 as possible were used during the design, including the rear machinegun mount, hatches, and observation devices.

Blueprints of the U-13 brass catcher, dated December 10th, 1941.

It's worth mentioning that the KV-7 was not referred to as an SPG in period documents. It was only called "KV-7 tank" or "assault tank". Nevertheless, it had all the features of an SPG. The KV-7 became the first SPG to be developed in the Urals that reached the prototype stage. According to factory documentation, repair tank #5161 built in September of 1941 was used for the prototype. The vehicle received a new casemate and armament, and some suspension elements were changed. 

Attempt at a Duplex

ChKZ treated the KV-7 project very seriously. The mention of every fifth tank was no joke. In parallel with production of the experimental prototype, factory #200 prepared for mass production of hulls. On December 30th, 1941, the chief engineer of factory #200, L.I. Eiranov, signed the technical requirements for a pilot batch of 20 hulls. It is not known how many hulls were really produced, but based on further developments, it is likely that the pilot batch was assembled.

KV-7 at factory trials, late Decembet 1941.

On December 27th, 1941 (10 days late), the KV-7 finally completed trials. Due to the hurry, no sight was ready, but there were some more serious complaints. According to the report, the screw type two-ball turning mechanism was poorly designed and led to high dispersion during firing. Captain P.F. Solomonov, the supervisor sent by GAU, made a list of over 10 defects that needed to be corrected. However, there was no time to fix most of them: the tank was awaited in Moscow on January 5th.

KV-7, side view.

On the scheduled day, trials were performed at factory #8 in Mytishchi. The vehicle was also inspected by a commission from GABTU, GAU, NKV, as well as Voroshilov and Kotin. When shooting from standstill, the gunner managed to fire all three guns at once on the third attempt, and the precision at 400 meters ended up being quite low. Trials showed that the rate of fire was 20-24 RPM. Individually, the guns fired about as quickly as they did in regular tanks, which cast doubt on the idea of volley fire. The F-34 could fire 3 rounds every 34 seconds, but the 45 mm guns could fire 5 times. The rate of fire was deemed unsatisfactory by the commission. In addition to unsatisfactory precision, especially when firing in a volley, the thickness of the front armour was deemed insufficient. A proposal was made to increase it to 110-120 mm. In addition, it was proposed that the SPG should instead have two 76 mm guns.

After receiving the results of the trials, Stalin personally wrote GKO decree #1110ss "On production of KV-7 and KV-8 tanks". The first point read: "cancel the proposed 3-gun KV-7 tank". The KV-7 was not cancelled entirely, but the pilot batch was never produced. On January 27th, 1942, tactical-technical requirements for a tank with two ZiS-5 guns were composed.

KV-7 with two ZiS-5 guns, March 1942.

As with the first variant of the KV-7, work on dual ZiS-5 guns was assigned to UZTM. L.I. Gorlitskiy directed both projects. The new system, indexed U-14, was also worked on by N.V. Kurin and G.F. Ksunin. According to dates on various blueprints, work began no later than January 25th, before receiving tactical-technical requirements. Work on the U-14 was finished in mid-February, and work on the modernized KV-7 began in the second half. The new tank wasn't built from scratch, the old KV-7 with the U-13 was used. Only the gun mantlet and ammunition racks were changed.

This is how the KV-7 sent to trials would have looked like.

The trials of the new KV-7 were planned for March 7th, 1942, consisting of 400 shots and a 50 kilometer drive. In reality, everything happened differently. Since ChTZ was very busy and the priority of the KV-7 was reduced, the tank only began trials on May 14th. A rate of fire of 6-7 RPM was reached, but the system was unbalanced, which resulted in the sights shifting with each shot. The ammunition rack was deemed inconvenient and the turning mechanism had to be operated with both hands. The trials ended and interest in the KV-7 waned.

The KV-7 resurfaced in October of 1942. During P.F. Solomonov's trip (now as a Major) to the Kirov factory, he inspected experimental SPGs. Mobility trials were also held. In November, GAU proposed that the tank should have a commander's cupola installed, all systems should be tuned, and it should be sent to military trials. The idea was binned, but the KV-7 managed to serve Soviet tank production. A planetary transmission developed at the Baumann Institute in Moscow under the direction of G.I. Zaichik. After that, the KV-7 ended up in storage at factory #100 and in December of 1943, the KV-7, along with the KV-9 and KV-12 were scrapped.

Last photo of the KV-7, made in the fall of 1943 in the storage area of factory #100 storage.

Waste Not, Want Not

In early January of 1942, GABTU started discussing the idea of installing something more powerful than a 76 mm gun into the KV-7. The initial proposal was the 152 mm M-10 howitzer.

In late January, S.A. Ginzburg prepared the requirements for a 152 mm howitzer on the KV-7 chassis. In the plan of work for 1942 approved by the People's Commissar of Tank Production Malyshev, this vehicle is listed at #59. According to the plan, Kirov factory was responsible for the chassis and UZTM was responsible for the gun. Blueprints were due on March 15th, an experimental prototype by May 1st, and mass production blueprints by May 10th. 300,000 roubles were issued for this project. This was not a lot of money compared to, say, the 212 project, but this was not a vehicle built from scratch, only the conversion of existing KV-7 hulls.

GAU had a mixed reaction to this new project, since the artillerymen still wanted a Br-2 gun on a KV-3 chassis. An artillery system on the KV-7 chassis seemed lacking. However, they soon had to shrink their appetites, as it became clear by early April that there won't be a bunker buster with a Br-2.

152 mm U-18 SPG

On April 15th, 1942, a meeting of the Artillery Committee was held to discuss self propelled artillery. It determined the direction in which Soviet SPGs developed. This is what was said on the issue of a heavy SPG:

"2) Bunker buster: 152 mm Br-2 gun on a special chassis from KV tank components

Assign the work to Kirov factory in cooperation with factory #221. Since the creation of a chassis for this project is difficult, consider it acceptable for the moment to settle for a design of this SPG.

Temporarily accept the installation of a 152 mm mod. 1937 gun-howitzer into a KV-7 hull. Assign this work to the Kirov factory."

Soon, instead of factory #172, UZTM was assigned work on the gun. Cooperation between ChKZ and Uralmash on the KV-7 project continued. The project, developed at Sverdlovsk since early 1942, was finally indexed U-18. As with the U-13 and U-14, L.I. Gorlitskiy directed the installation of the ML-20 into the KV-7.

Reconstruction of the overall view of the U-18.

For various reasons, the installation of the 152 mm gun into the KV-7 casemate lagged behind. The draft was only ready by August 4th and presented a month later, on September 3rd, 1942. UZTM engineers tried to satisfy the military's requirements while altering the KV-7 as little as possible. As a result, the U-18 consisted of only 13 components, while the KV-7 hull and casemate had no changes. This kind of approach can be easily explained by this phrase from the U-18's description:

"The KV-7 is most suitable as the chassis for this SPG. Dozens of hulls and turrets for this tank are present at the Kirov factory in Chelyabinsk, designed for one 76.2 mm and two 45 mm guns."

It would appear that this approach by the UZTM design bureau was perfect for using up these hulls, but that just makes the ending to this story that much more surprising. On September 24th, 1942, the chief engineer of UZTM, M.G. Umnyagin, received a letter from the chief of the 6th department of the GABTU BTU, Engineer-Colonel Kovalev.

"In response to your letter #3655/48s about the U-18 SPG, an analogous project was proposed by comrade Petrov on September 12th and was discussed by the Technical Committee of the Commissariat of Armament."

Suddenly, the story of the U-18 was over before it even began. The U-18 and U-19 SPGs designed under Gorlitskiy's direction remained on paper and sank so deep into the archives that they were completely forgotten. Only their indices remained, which, due to a lack of information, were erroneously assigned to projects developed at factory #8 under F.F. Petrov. Each of them is worth their own story.

Original article by Yuri Pasholok.

Double Barrels from Perm

In December of 1942, Soviet tank designers had the idea of creating a multi-barreled SPG on a modified T-34 chassis. One of the projects was developed at the Perm OKB-172, an unusual dual howitzer indexed SU-2-122. The project didn't move past the blueprint stage, and remained in the archives. What was it like?

The idea of multi-barreled artillery systems that could fire a salvo occupied the minds of tank designers from many countries. In one case, a design made it to mass production and even to battle: the light Marmon-Herrington MTLS-IGI4, armed with two 37 mm guns. 145 tanks were built, used in combat in the Pacific.

In the USSR, the most famous multi-barreled tank was the KV-7.An experimental prototype of the assault tank (it was never called an SPG) was designed in November of 1941 in Chelyabinsk on Stalin's orders. The KV-7 was armed with two 45 mm guns and one 76 mm ZiS-5 gun. The KV-7 could fire all three guns at the same time. A prototype was finished in December of 1941, and mass production was expected. Archive data reveals that KV-7 hulls were ordered before trials even began, and 20 of them were made. Trials in January of 1942 showed the poor execution of the simultaneous firing idea. The KV-7 was converted to use a pair of 76 mm guns, but the results were largely the same.

While the KV-7 was being worked on, a project on the T-34 chassis was developed in Nizhniy Tagil at factory #183. The tank, indexed T-34-3, had two 45 mm guns and one 76 mm gun in a rotating turret. Unlike the KV-7, this tank did not make it to metal. Activity on this topic ceased, but not for long.

In the middle of December of 1942, the Technical Council of the People's Commissariat of Armament composed tactical-technical characteristics for an SPG with two 122 mm M-30 howitzers. This request was a project of personal initiative, since it did not receive high priority. It was proposed by Major-General of the Artillery Engineering service, A.A. Tolochkov, who was the chief of the experimental designs department. The requirements were as follows:

• The armament must consist of two 122 mm howitzers, using barrels and breeches from the M-30.
• The guns must have the same mount, but have separate recoil brakes, as similar as possible to those on the M-30.
• The mount and recoil mechanisms must be protected by armour.
• The vertical traverse must be from -5 degrees to +15 degrees, horizontal traverse of 15-20 degrees.
• The front armour must be 70 mm thick, side armour 30 mm, roof and rear 15-20 mm.
• T-34 components must be used as much as possible.
• The ground pressure must not exceed that of the T-34.
• The guns must be able to fire individually or simultaneously.
• 1 or 2 additional DT machineguns must be available as additional armament.

On May 12th, 1943, the GAU Artillery Committee received a letter from the city of Molotov (the name of Perm from 1940 to 1957). The letter, sent by OKB-172 chief, NKVD Lieutenant-Colonel N.A. Ivanov, contained two projects. One was a heavy 203 mm SPG on the KV-1S chassis, the other a medium SU-2-122 SPG, the same one that requirements were created for in 1942. Both projects were supervised by A.F. Smirnov.

It's worth mentioning what OKB-172 was. It was none other than a prison. The majority of its staff were imprisoned engineers that used to work in Leningrad. In 1941, they were evacuated to Perm. A wide variety of projects were created within the walls of OKB-172, including the 45 mm mod. 1942 gun. Smirnov, the supervisor of the SU-2-122 project, also worked on the MU-2 and B-2-LM naval guns. A part of the prisoners were pardoned due to their excellent work on June 19th, 1943, by decree of the State Committee of Defense #3612. The decree was proposed by Beria himself. As free men, Smirnov and others continued work in OKB-172.

The unusual requirements led to an unusual, yet very well thought out project. Aside from 12 pages of description, it had 5 pages of blueprints with overall views of the vehicle as well as the artillery system. It was obvious that the stock T-34 chassis was not enough for two 122 mm guns. The hull had to be lengthened by 890 mm, and an extra road wheel added. Remembering that T-34 parts had to be used as much as possible, the designers left the engine compartment and the driver's compartment without changes. Unlike the SU-122, where the driver's seat changed and the machinegun operator was done away with, the SU-2-122's front was the same as on the T-34. This was one of the things that lengthening the hull allowed to achieve. The longer hull also improved balance. Unlike the SU-122, the SU-2-122 did not increase pressure on the front road wheels.

The turret was replaced with a casemate (or, in terminology of the day, an immobile turret). In order to increase the available space, the sides of the casemate were wider than the top of the hull. The casemate sides were sloped to improve protection. As was specified in the requirements, the front armour was thickened to 70 mm.

The guns were mounted on a frame, attached to the front of the casemate. This solution, common for Soviet medium and heavy SPGs, had many advantages. A frame did not require a massive floor mount, which decreased complexity and freed up space in the fighting compartment. The artillery system was designed very well. The oscillating part of the M-30 (which, by the way, was produced at factory #172, where the design bureau was based) remained unchanged. Both howitzers were covered by one mantlet. The aiming mechanisms and sights were to the left of the guns. The gunner's seat was also placed on the left, and moved with the guns. The DT machinegun was to the right of the guns, the ball mount and mantlet borrowed from the T-34.

The crew of the SU-2-122 consisted of 6 men. The crewmen could move about freely, due to the size of the casemate, and even stand up fully. Each M-30 had its own loader. The SU-122 had one loader and one breech operator, working in much more cramped conditions. Here, loading was much simpler. The ammunition rack consisted of 70 shells, placed along the rear of the fighting compartment. This placement eased the work of the loaders. The estimated rate of fire of this gun would be 4-5 salvos per minute.

No further work was done on the SU-2-122. The design of a tank is a difficult process, and any decision has a drawback. In this case, it was the size and weight of the vehicle. The longer hull and roomy fighting compartment did not come for free. In this case, the mass of the SPG was estimated to be 34.5 tons, while the SU-122 weighed only 29.6 tons. The ground pressure increased, and average offroad speed decreased to 15 kph. The height was also an important parameter: the SU-2-122 was 2940 mm tall (the roof was 2740 mm off the ground), which was taller than the SU-152.

The main problem with the SU-2-122 was not the height or the weight. In the spring of 1943, production of the SU-122 was underway, and it did not require the T-34 chassis to change. Even the SU-122 was not enough for the military in May of 1943, as a captured Tiger was already tested, and showed that an SPG should have an 85 mm gun with AA 52-K gun ballistics. Nobody needed this double barreled tank, especially after the experience with the KV-7. As a result, this project remained in the archives, where it was discovered very recently.

Original article by Yuri Pasholok.

Green Elephant

This project, designed in 1942 by the Ural Heavy Machinery Factory could have been the heaviest Soviet SPG. In accordance with the saying "fight fire with fire", engineers proposed a well armed, well protected, but not very mobile "pillbox on tracks" to attack enemy fortifications, the U-19 SPG. What prevented this project from becoming a reality?

Bunker Buster Project

In early 1942, it was clear that the KV-3 wouldn't take off in Chelyabinsk. Even if the tank and its engine were still listed as active projects, they were all but forgotten. The plans to build the 212A SPG on the KV-3 chassis were dropped in April of 1942, but the idea of a heavy assault gun remained. This time, the KV-7 served as the foundation, as its casemate allowed the use of a 152 mm ML-20 gun-howitzer. The project to mount this gun in a KV-7, indexed U-18, began at UZTM under the supervision of L.I. Gorlitskiy.

However, the compromise of using the KV-1 chassis and an ML-20 gun was not entirely satisfactory. The KV-1 chassis was acceptable, but the ML-20 was notably inferior in its destructive power to the 152 mm Br-2 high power gun, which was considered the gold standard for bunker busters. As a last resort, the B-4 howitzer was considered acceptable, since both could be installed on the same mount. Unlike the Br-2, less than 40 of which were made, the B-4 was a fairly common artillery system.

At the start of 1942, two organizations were involved in the design of heavy SPGs. The Moscow Baumann Machinebuilding Institute was tasked by the NKV to work on bunker busters armed with either a 152 mm Br-2 gun (SU-Br-2) or 203 mm B-4 howitzer (SU-B-4). The second organization was factory #221, the producer of Br-2 guns and B-4 howitzers. In March of 1942, the factory design bureau finished proposals for the BR-33P and BR-33G SPGs. Both were based on components from the T-34 medium tank. Documentation showed that the BR-33P would be armed with a 152 mm Br-2 gun, and the BR-33G would be armed with a B-4 howitzer. After a review, it was decided that these vehicles would not be produced, as they did not match the requirements for bunker busters.

The Ural variant

In April of 1942, the task of creating a 203 mm assault gun was given to the UZTM design bureau. Judging by correspondence, this vehicle was ordered by J.Ya. Kotin, Deputy People's Commissar of Tank Production at the time. It is interesting to note that, unlike the U-18, the U-19 was not present in reports. It is likely that the project had a low priority and was treated as a backup plan. Nevertheless, the U-19 was completed before the U-18. The overall description of the vehicle was finished in May, blueprints in June, and the project was sent to GAU and GABTU on August 12th, 1942, three weeks before the U-18. The backup plan was also thought out a lot more thoroughly than the main one.

The U-19 consisted of a 203 mm mod. 1931 howitzer (B-4) on the KV-1 chassis. The goal of this vehicle was the destruction of fortifications that were too tough for smaller guns. Like the KV-7, the KV-1 hull was altered: the turret platform was removed, the engine bulkhead was made removable, the fuel tanks and air intakes were altered. The oscillating part of the B-4 remained unchanged, in order to reduce the time required for conversion. The turret was replaced with a massive casemate, partially overlapping the engine compartment, which could cause difficulty when servicing the engine.

The thickness of the front plate was 75 mm, the sides were 60 mm thick, the rear 40 mm, and roof 30 mm. A large hatch was included in the rear for installing the howitzer, which had a smaller hatch in it for crew evacuation. According to the specifications, the roof was removable. Since the main purpose of the U-19 was the destruction of fortifications, the gun elevation was capped at 10 degrees. The horizontal traverse was minimal, only 4.3 degrees each way, same as on the B-4 howitzer.

The requirement to make minimal changes to the chassis while also providing a respectable level of protection resulted in an interesting product. According to calculations, the U-19 would weigh 66190 kg, which was even heavier than the 212A SPG. Since vehicles have a tendency to be heavier in metal than on paper, it was possible for the U-19 to be the heaviest Soviet assault SPG, surpassing even the fully armoured SU-14. Putting the B-4 howitzer in a closed casemate also required a height of 3510 mm, which was only 50 mm lower than the fully armoured SU-14. The creators of the U-19 understood that the large SPG was a perfect target for the enemy, which is why it was to be escorted by regular tanks on the battlefield.

A predictable outcome

The project led to predictable results. On September 9th, 1942, the chief engineer of UZTM, M.G. Umnyagin, received a letter written by the chief of the BTU, Engineer-Colonel Afonin.

"To your letter #3707/48s sent on August 24th, 1942, regarding the project "U-19 203 mm howitzer on the KV-1 chassis", I reply that:

1. The mass of the U-19, equal to 66 tons, and the V-2K engine will not result in reliable movement at the required speeds. Furthermore, the transmission of the KV-1 is designed for a 40 ton vehicle, and cannot work reliably in a 66 ton vehicle.
2. The SPG makes for a well noticeable target due to its large height (3.51 meters) and wide upper section (immobile turret). 
3. The armour is weaker than that of the regular KV-1 tank, as a result of which, the crew will not be protected at close ranges.
4. If the suspension is damaged, the gun will only work within a 9 degree arc, as the U-19 does not have a rotating turret.
5. Due to the mass of the SPG, it will not be possible to tow damaged SPGs from the battlefield.
6. The off-road performance of the SPG, judging by its effective horsepower (9 hp/ton) and ground pressure (0.98 kg/cm^2) will be poor.

From the above, I conclude that further development of the U-19 SPG is illogical."

This reaction from GABTU was well founded. On one hand, the mass of the SPG was similar to that of the 212A, on the other hand, the 212A was based on the KV-3, with a much more powerful engine. The project was also submitted at a bad time, since the lighter 42.5 ton version of the KV-1, indexed KV-1S, just entered production at ChKZ. A design that would weigh 1.5 times as much as the base vehicle was like a red rag shown to a bull. In these conditions, the chances of the U-19 reaching even the prototype stage was nil.

The project was sent to the archives, and few mentions of it exist in other documents. This fact played a mean trick on the U-19: since the only information available on the project was "B-4 on the KV-1 chassis", it was confused with another vehicle. A series of publications, including encyclopaedias, show an illustration of the U-3, a 203 mm howitzer installed in a SU-152, which has no relation to the U-19 project. Even the developer was different: this project was designed by the factory #9 design bureau, led by F.F. Petrov.

Original article by Yuri Pasholok.

KV-7 and KV-8 Trials

"Act of Examination and Practical Gunnery Trials of Experimental KV-7 and KV-8 Prototypes produced by the Kirov Factory

The examination of tanks happened on January 5th, 1942, at the factory #8 proving grounds at Mytishi. Present: [long list of names]

KV-7 Tank

The experimental KV-7 breakthrough tank has a suspension and transmission identical to the production KV-1 tank. Instead of a turret with 360 degrees of traverse, it has an immobile casemate with three guns, two of which are 45 mm guns and one of which is 76 mm (F-34). The guns have horizontal traverse of +/- 7.5 degrees, -5 degrees of depression, and 15 degrees of elevation. The guns have separate triggers. There are also two DT machineguns.

Ammunition: 200 45 mm shells and 93 76 mm shells.

The front armour is 100 mm thick, the turret armour is 105 mm thick, and the gun mantlet is 100 mm thick.

Crew: 6.

After inspection and trials, the following was observed:

1. The driving performance is satisfactory.
2. The armour of the hull and turret is insufficient.
3. The practical rate of fire (5-6 volleys per minute) is satisfactory.
4. The layout of the guns is satisfactory.
5. The precision is unsatisfactory.

It is necessary to:

1. Increase the turret armour thickness to 115-120 mm, increase the front hull armour to 110 mm.
2. In order to improve gun precision, rework the turning mechanism of the gun mount. Improve the optical sight installation. Improve the firing mechanism in order to fire from all three guns at once.
3. Consider it necessary to subject one of the January-February production tanks  to further trials according to the UVNA GAU KA standards in order to evaluate the correction of aforementioned flaws in the pre-production batch.
   Trials must be performed before February 15th, 1942.

KV-8 tank

The experimental KV-8 flamethrower tank has a suspension, transmission, and armour identical to the production KV-1 tank. The tank turret has a 45 mm gun with an ATO-1 flamethrower and a DT machinegun instead of a 76 mm gun with a DT machinegun.

The angle of elevation of the armament is 20 degrees. The angle of depression is -5 degrees. The turret can rotate 360 degrees.

Ammunition: 85 45 mm shells. 90 shots (10 meter range) for the flamethrower.

Crew: 4.

After inspection and trials, the following was observed:

1. The driving performance is satisfactory.
2. The flamethrower range is satisfactory.
3. The design of the flamethrower and ammunition storage is satisfactory.

It is necessary to:

1. Turn off the ignition flame between shots.
2. Prevent the penetration of gasoline and fire through the gun mantlet into the tank.
3. Guarantee at least 60 shots from the flamethrower given a normal rate of fire and full tanks.
4. Check and correct all defects in the ATO-1 automatic mechanism design.
5. Consider it necessary to provide a January-February production KV-8 tank for trials in order to evaluate the correction of the aforementioned flaws in the pre-production batch.

The commission considers it necessary to develop and install a twin 76 mm gun system on the KV-7, as well as develop more powerful 85 and 122 mm gun systems for this tank.

The design bureau of the Kirov factory is tasked with the design of these experimental SPGs."

RGASPI 664-2-32

The commission's suggestion was taken, and on the next day, Stalin issued decree #1110ss ordering the replacement of the three gun system on the KV-7 with a two-gun system. The same decree approved the KV-8 for production and ordered the development of a KV-1 with a 122 mm howitzer (later indexed KV-9).

Stalin Shutdown

The opinion that Stalin was somehow all-powerful and nobody dared refuse his requests. However, that is not true. Here is a response to a request for 45 mm guns for Stalin's pet KV-7 project.

"To the Deputy People's Commissar of Tank Production, comrade Zaltsmann
On the issue of delivery of 45 mm guns for coaxial mounts.

The production of 45 mm guns in coaxial mounts for KV tanks is not mentioned in any GKO decree. Therefore, the requested 45 mm guns will not be sent to the Kirov factory (ChTZ).

Deputy Chief of Red Army GAU, Major-General of Artillery, Hohlov
Military Commissar of the Red Army GAU, Divisional Commissar Novikov"

CAMD RF 81-12104-422

After spelling out "get bent" in two entire paragraphs, nobody ended up getting shot.

World of Tanks History Section: SU-152, Soviet Beast-Killer

During the Soviet-Finnish War of 1939-1940, the Red Army hit a powerful defensive line in Karelia, the Mannerheim Line. Soviet soldiers were greeted with an unpleasant surprise: concrete pillboxes that could onl be destroyed with large caliber artillery.

Delivering a heavy and clumsy gun to a battlefield is not an easy task. The best solution is a gun that can drive into battle by itself. Soviet commanders remembered that work on self propelled artillery has been slowly coming along since 1931. The topic was dusted off. Two factories, Kirov and #185, got to work. By Spring of 1940, experimental vehicles have been designed: SU-14-2, T-100Y (SU-100Y), and KV-2, which may be called a tank, but was more of an assault gun with a turret. The SU-100Y did not make it in time for the war, but work on bunker busters continued. When the Great Patriotic War began, the design center was moved from Leningrad to Sverdlovsk.

From three barrels to one

The basis for the SU-100Y was the T-100 heavy tank, which lost out to the KV and did not enter production. This also put a cross over the SU-100Y. All heavy SPGs had to use the KV chassis.

In November of 1941, the Chelyabinsk Kirov Factory (ChKZ) designed the KV-7 assault tank, a vehicle with an immobile casemate carrying three guns. The project was curious, but its combat usefulness was doubtful. In fall of 1942, the Red Army GAU ordered ChKZ to develop a large caliber SPG, placing the ML-20 152 mm gun in the KV-7 hull. The project was headed by Lev Sergeevich Troyanov, the most experienced Soviet designer of SPGs.

Troyanov decided to install the casemate on a KV-1S heavy tank chassis. The wooden model and project documentation were ready at the end of 1942. In early January of 1943, the project was scheduled for a demonstration to the client. By this point, it was indexed KV-14. Two projects were demonstrated. First was designed by the factory #9 design bureau chief Fedor Fedorovich Petrov. The project was more complete, but needed many modifications of the KV-7 hull and the gun. Working blueprints for Troyanov's project were only partially complete, but his project required significantly less modifications to mass produced tanks and guns.

Stopping power

On the day after the demonstration, Joseph Stalin signed an order of the State Committee of Defense to build a prototype of the new SPG by January 31st, in less than a month. Kirov factory not only managed to deal with such a harsh quota, but finish a week early.

Trials of the new SPG were conducted from February 1st to February 5th. The KV-14 drove to the proving grounds at Chebarkul. This was a difficult trial: the SPG drove through a snowed-over highway in temperatures of -42 degrees. Water got in the engine, it kept stalling. The SPG travelled the 85 km from Chelyabinsk to Chebarkul in 13 hours.

After 234 shots, no defects were discovered in the gun or mount. The gun could not achieve the requested 3-4 RPM, but the result of 2.8 RPM was also not bad. No defects were found in the engine or transmission. There were design flaws that needed work, but by February 9th, the KV-14 was adopted into the Red Army.

And so, the USSR received an SPG with no equal anywhere in the world. It had a powerful gun, the armour of a heavy tank, and what was no less important for a fighting machine, a compact size. What's most important is that the Red Army received a universal SPG, capable of dealing with any combat mission. From the end of April of 1943, the vehicle was indexed SU-152.

The Beast-Slayer's debut was at the Battle of Kursk, in which 24 vehicles of this type took part. The small numbers did not make a large impact on the flow of events, but it turned out that, of all Soviet vehicles of the time, only a shot from this SPG could guarantee the destruction of any German vehicle of the time. It was not necessary for a 152 mm shell to penetrate enemy armour. Hero of the Soviet Union Major Sankovskiy demonstrated the combat potential of the SU-152: his vehicle destroyed 10 tanks in one battle.

The SU-152's effectiveness is also highlighted by the fact that it remained in service with Soviet tank forces until 1958.

Yuri Pasholok's book "SU-152 and other SPGs on the KV chassis" was referenced when writing this article.

Original article available here.

ZiK-20

I posted about proposed heavy SPGs before, but let's take a look at a specific one, the Kalinin factory version.

"Main elements of the tactical-technical characteristics and production of an experimental 152 mm self-propelled howitzer.

1. Outline
1. The 152 mm self propelled howitzer is a self propelled gun with the oscillating part of a 152 mm model 1937 corps howitzer (ML-20) installed on a KV tank chassis in an immobile prismatic turret.
2. Tactical purpose
1. The 152 mm self propelled howitzer supports motorized and infantry units when penetrating enemy lines and fires on counterattacking enemy forces.
2. The 152 mm self propelled howitzer largely fires directly at close ranges, moving in shorts bursts from line to line. In rare cases, the vehicle opens indirect fire. Firing on the move should be seen as a rare case.
3. Technical requirements
1. The SPG is produced with minimal changes to existing designs (152 mm ML-20 howitzer, KV-7 tank).
2. The dimensions of the vehicle should be as close as possible to the dimensions of the KV-1. The increase in height and bore axis height should not be greater than 100 mm.
3. The mass of the vehicle with crew, ammunition, and a full load of fuel should be within 45-50 tons.
4. Primary characteristics of the SPG:
1. Caliber: 152 mm
2. Vertical range: -2 degrees to 15-20 degrees
3. Horizontal range: +/- 5-6 degrees
4. Aiming speed: 30-45 minutes in one rotation of the flywheel
5. Recoil length: no more than 850 mm
6. Recoil resistance: no more than 30-35 tons
7. Maximum rate of fire with correction of aim: 8 RPM
8. Force on aiming mechanism when vehicle is stopped: no more than 3 kg
9. Ammunition capacity: 30 shells
4. Usage requirements
1. The SPG is serviced by a crew of 6: commander, mechanic-driver, gunner, loader, breech operator, radio operator/machinegunner.
2. The oscillating armour should allow for easy access to recoil mechanisms.
3. The gunner's workspace (seat, aiming mechanisms, sight) should be usable freely and allow for convenient and non-exhausting aiming of the howitzer when in place or in motion. The effort required to operate the trigger mechanism should be no greater than 8 kilograms. It is desirable that the trigger mechanism be placed on the handle of the elevation flywheel.
4. The commander's workspace should be equipped with a stock cupola from the KV-1S.
5. The howitzer should have a guard rail, a collapsible tray for readying a shot, and a blocking mechanism to prevent firing until loading is completed. When developing the tray, ensure that it is positioned in a way to make loading take the minimum amount of energy.
6. The ammunition rack should be robust, resistant to deformation, and provide free and comfortable access to ammunition with the goal of maximizing rate of fire.
7. The placement of ammunition should take into account the actions taken by the loader and breech operator: the loader prepares and places a shell into the breech, the breech operator opens and closes the breech, as well as inserting the propellant into the breech.
8. The manual extractor, wrenches for installing detonators, and the rammer are secured on the walls of the turret.
5. Requirements for the turret and its devices
1. The rear of the turret should have a hatch for the crew, loading ammunition, and emergency ventilation.
2. The sides of the turret should have ports for firing a pistol and submachinegun, as well as slits for additional observation. The rear wall should have a ball mount for a DT machinegun.
3. The crew's personal weapons should be kept in a reliable and convenient holder next to their workspaces.
4. The roof should have a hatch next to the commander's workspace for firing signal flares, and the rear wall should have a hatch suitable for throwing hand grenades through.
5. The lights within the turret should provide for comfortable gun maintenance and combat action.
6. Communication is performed through a stock tank radio and a TPU.
7. The front turret armour should be no less than 90 mm, 50 mm side and rear. The sides should have a slope of 30 degrees from the vertical. 
8. The commander's workspace should allow for convenience when working with a map or a clipboard.
9. Each crewman should have a comfortable seat for travel and rest. The seats of the loader and breech operator should be folding, and should not constrict their actions in battle.
10. The inside of the turret should provide storage for a first aid kit, emergency rations, and a supply of drinking water."

CAMD RF 81-12038-33

World of Tanks History Section: KV-7

In November of 1941, a new assault tank started development in Chelyabinsk. The project started due to a request from Stalin personally in response to the military's desire for the famous Soviet heavyweight, the KV, with increased firepower.

The tank was indexed KV-7. It was to be armed with three guns: one 76 mm and two 45 mm. The guns could fire independently or all at once. SKB-2, led by G.N. Moskvin, was responsible for brining the project to life.

It was physically impossible to fit three guns into a KV-1 turret, so a prism-shaped casemate was used instead. Many elements of the KV's turret were used in its construction: the MG mount, hatches, observation devices.

N.N. Efimov and K.N. Ilyin developed the artillery system, aided by the famous engineer L.I. Gorlitskiy. It received the index U-13. All three guns shared a mantlet. The 76 mm gun was placed in the center, and the 45 mm guns to the sides. Factory trials on December 27th revealed many deficiencies. The aiming mechanism was considered poorly planned, as were the case catcher, gunner's seat, and several other elements.

On January 5th, 1942, a second round of trials was performed. All three guns fired at once only on the third try. The precision at 400 meters was insufficient. Furthermore, the 45 mm and 76 mm guns had varying rates of fire, which cast doubt on the idea of the multiple gun system. The gunner had difficulty using the sight, and it was impossible to use the forehead rest.

On January 6th, Stalin ordered the replacement of the three gun mount with a dual 76 mm gun mount. L. Gorlitskiy developed the U-14 system, using two ZiS-5 guns. It was mounted on the KV-7 instead of the U-13. The casemate remained the same, only the gun and ammunition racks changed.

The double barreled KV-7 began trials on May 16th, 1942. Again, several faults were found. The gun elevation increased after every shot. The aiming mechanisms were very heavy. The cassette based ammo rack was considered unsuccessful, and was replaced with an open crate design.

The second round of trials never started. The Chelyabinsk tank factory threw all its resources at the KV-1S project. Interest in the assault tank waned. Although it still drove over one thousand kilometers to test its improved transmission, its story came to an end at the end of December of 1943. The SPG was disassembled and scrapped. Armour cut up to produce KV-7 hulls was used in other vehicles.

The design of the KV-7 was a mistake. However, its impact on tank building was immense, as it was a pioneer among heavy SPGs, including the legendary "Beast Slayer" SU-152.

Original article available here.

KV-7 Guns

The origins of the KV-7, an SPG on the KV-1 chassis with multiple guns, began in November of 1941 at the Kirov factory, after evacuation to Chelyabinsk.

CAMD RF 81-12104-79

"November 25th, 1941

According to the personal decree of the People's Commissar of Defense, comrade Stalin, the Kirov factory (city of Chelyabinsk, ChTZ) is developing a gun mount for the KV tank (two 45 mm tank guns and one F-34 76 mm tank gun). 

In order to develop these mounts, four 45 mm tank guns are needed urgently. 

In order to mass produce KV tanks with multiple guns, 180 45 mm guns with breeches should be delivered to the Kirov factory in December of 1941, and 260 in January of 1942, without the mount, recoil brakes, semi-automatic devices, and sights."

90 KV-7s in December was a very liberal estimate. The KV-7 only began trials in December, with disappointing results.

CAMD RF 38-11355-668

"[day cut off] December, 1942

The KV-7 gun mount that underwent trials on December 27th, 1941, requires correction of defects and urgent proving grounds trials.

Without performing trials, the mount cannot be equipped with proper sights. The installed TMFD-8 sight merely marks the place where a sight would be placed, and must be altered for use, specifically with new markings. Furthermore, attachment of the sight at only one point is undesirable.

The robustness trials performed at the Kirov factory were only done with stock combat rounds. Testing rounds were not used. No measurement of parts was performed. The parts must be tested with increased strength rounds.

The turning mechanism of this system, screw type with two ball and socket joints, is of suboptimal design, and results in high dispersion during firing. This mechanism will require constant maintenance and observation, as wear on the balls will reduce precision and accuracy.

A redesign of the turning mechanism is desirable. A sector type mechanism is preferable. Install limiters on turning and elevation mechanisms. The brass catcher needs a redesign. Lengthen the left and right cheeks by at least half of the length of the breech, otherwise the crew is not protected from the guns' recoil. The overall width of the catcher can be reduced, but the height of the walls must be increased. 

Change the position of the forehead rest. It is inconveniently located, and the gunner cannot use it.

The firing mechanism pedal needs to be moved. Its location prevents placing 76 mm shells in cassettes.

The gunner's seat needs to change, most notably the back should be curved.

At maximum depression angles, the recoiling guns can break the ceiling lamp. Design the compartment in such a way that the recoil indicator gauges are illuminated.

Connect the driver and gunner with a communication device, as rough aiming is done by turning the tank."

However, only a few days later, Stalin made a decision to change the armament. 

"On production of KV-7 and KV-8 tanks

1. Stop work on the 3-gun KV-7.
2. Equip the KV-7 with two 76 mm guns with +/- 7.5 degrees of horizontal range, +15 degrees of gun elevation, and -5 degrees of gun depression.
3. ..."

RGASPI 664-2-32

Work on this new tank also took a long time.

"The KV-7 tank was completed on May 11th, 1942, and trialled on the 14th at the Kopeisk proving grounds. 17 shells were fired, of those 5 were single shots and 12 in salvo. The target was 1.5 by 1.5 meters, 800 meters away. As a result of this data, the following conclusions can be made:

1. The precision and accuracy when firing from the spot is good with the paired gun system. After calibration, 11 shells landed in an ellipse with the larger diameter 40 cm in length, and smaller diameter 13 cm in length. 
2. The rate of fire is 6-7 salvos per minute. Due to the unbalanced system and non-self-braking elevation mechanism (like the sector-type elevation mechanism) installed, the elevation increases after firing by 25 mils.
3. The turning mechanism is heavy, and needs to be turned with both hands, which is unacceptable.
4. The shell cassettes in the turret bay cause difficulty when working and must be replaced with an open type ammunition rack.
5. The firing mechanism is too heavy when firing in salvo, and should be lightened by a factor of at least two.
6. There is no mechanism for artificial recoil, which would also need a hatch in the rear. That hatch should also be usable for crew evacuation. 

I ask for further instructions on this gun system."
CAMD RF 38-11355-639