Howitzer T-34

"July 20th, 1942

To the director of Kalinin factory #8, comrade Fratkin
Sverdlovsk

CC: Chief of the NKTP Technical Department, Engineer Colonel Ginzburg
CC: Chairman of the NKTP Technical Council, Satel

RE: conclusion regarding installation of a 122 mm howitzer in a T-34 tank turret

The project of a T-34 tank with a 122 mm howitzer developed on factory #8's initiative that you sent attached to letter #1430s was reviewed by the GAU Artillery Committee.

The project consists of installing an experimental 122 mm tank howitzer into a T-34 tank with the condition of maintaining the existing turret ring.

The First Coming of the IS-2

The 122 mm U-11 gun designed in the fall-winter of 1941 was rather controversial. Its designers succeeded in their task of installing a gun with the ballistics of the M-30 in a minimally altered KV-1 turret. However, the howitzer had a low rate of fire, and its penetration characteristics were poor. As a result, the planed KV-9 batch remained on paper. Nevertheless, the GABTU did not give up on the idea of a howitzer tank. Despite opposition from the GAU, work on howitzer tanks continued in 1943.

Mistimed Improvement

A notable event in the history of Soviet tank building took place in December of 1942. The SU-35, the first Soviet medium SPG, was put into production. There was the SG-122 that predated it, but it was a conversion of the German StuG III. The SU-35, however, was an entirely domestic design. Due to the urgency, the SU-35 was put into production without a second prototype. The SPG went into production straight from the drawing board. Nevertheless, the issue of modernization was raised at the highest levels in January of 1943. The result of the ensuing work was the SU-122M. However, this assault SPG's fate was not as fortunate: it never made it to production.

Through Adversity to the SU-122

It was clear by the spring of 1942 that work on a medium SPG on the T-34 chassis with an 85 mm gun in a rotating turret hit a dead end. The result of this work, which started back in the summer of 1940, was the U-20, which the military considered unsatisfactory. The project didn't leave the drawing board. Later, development of Soviet SPGs took a different path. A significant influence was the study of a captured StuG III Ausf. B. Later, factory #592 built a Soviet version on its chassis, called SG-122. It was clear, however, that converting foreign vehicles was not the end.

T-34 with U-11

"To the director of Kalinin factory #8, comrade Fratkin, Sverdlovsk

CC: NKTP Technical Department Chief, Engineer-Colonel Ginzburg, Sadovo-Sukharevskaya 9.11.

CC: NPTK Technical Council Chair, comrade Satel, 35 Gorkiy St.

July 20th, 1942

The design sent to us for review in letter #1430s of a 122 mm U-11 howitzer in a T-34 turret, designed under the initiative of factory #8, was reviewed by the Artillery Committee of the GAU.

The design describes the installation of an experimental U-11 122 mm tank howitzer into a new T-34 tank turret, while maintaining the existing turret ring. Since the proposed fighting compartment only fits two men to service the gun, which is insufficient for the howitzer to work normally, the project is not of interest and is rejected.

Considering that the installation of this howitzer in the larger KV tank turret resulted in insufficient comfort of service and rate of fire, the development of this project is nonsensical.

In order to avoid unproductive waste of effort and resources, the Artillery Committee consider it prudent to seek approval from the GAU before projects are started.

Deputy GAU Chief and ArtKom chair, Major-General of Artillery, Hohlov

ArtKom Military Commissar, Regimental Commissar Vasiliev"

CAMD RF 81-12038-32

Here is the proposed design.

Howitzer KV

So called artillery tanks, or support tanks, appeared in the mid-1920s. The British pioneered the concept, equipping their Medium Tanks Mk.I and Mk.II with 94 mm howitzers. Similar tanks were also built in other countries. The USSR was no exception. The first work on artillery tanks in the USSR began in the early 1930s. The BT-7 Artillery was the best known vehicle of this type. The KV-2 can also be placed into the artillery tank category, with some leeway. The artillery tank concept was rejected by the USSR before the start of WWII. Nevertheless, the KV-9 was designed in early 1942, a tank that fully fit into the category of support tanks.

IS, First Series

"Order of the People's Commissar of Tank Production of the USSR #104ss
Moscow
February 25th, 1943

On the construction of experimental IS tanks

To fulfil State Committee of Defense decree #2943ss, issued on February 24th, 1943, I order that:

1. The director of the Kirov factory, comrade Dlugach, director of factory #200, comrade Sherbakov, and chief engineer of the Kirov factory, comrade Kotin, produce two experimental IS tanks at the Kirov factory: one with the 122 mm gun (U-11), the other with a 76 mm gun (F-34), and provide them for proving grounds trials by March 10th, 1943.
2. The GOKO decree defines the following main characteristics of the IS tanks:
1. A maximum weight of 39.5 tons for the tank armed with the 122 mm U-11 gun, including ammunition, fuel, and crew.
2. A maximum weight of 38.5 tons for the tank armed with the 76 mm F-34 gun, including ammunition, fuel, and crew.
3. Armour:
1. Front: 120/100 mm (cast)
2. Side: 90 mm (rolled)
3. Top and floor: 20 mm 
4. Rear: 60 mm (sloped at 45 degrees)
5. Turret: 100 mm (sides)
4. Maximum speed: 55 kph.
5. Transmission: 8 speed gearbox, planetary turning mechanism, planetary final drives.
6. Engine: 600 hp V-2K
7. Ammunition:
1. No less than 30 shells for the IS tank with a 122 mm gun.
2. No less than 80 shells for the IS tank with a 76 mm gun.
8. Crew: 4
9. Machineguns:
1. With a 122 mm gun: 2 (coaxial and hull)
2. With a 76 mm gun: 3 (coaxial, turret rear, and hull)
10. Fuel capacity: 500 kg

..."

CAMD RF 38-11355-1485

KV-9 Trials

"According to order #012 of the NKO and the order #48s of the People's Commissariat of Tank Production, the commission led by Major-General of the tank forces comrade Ponov tested the KV-9 tank armed with the 122 mm M-30 howitzer from February 2nd to February 11th, 1942.

1. Goal of trials.

A KV-9 tank produced by the Kirov factory on the chassis of the KV-1 tank (see attachment #1) was submitted for trials. The KV-9 is armed with a 122 mm U-11 (M-30) howitzer designed by the Ural heavy machine building factory. The 122 mm tank howitzer is based on the stock divisional M-30 howitzer (see attachment #2). The KV-9 turret differs from the KV-1 turret in the following ways:

1. Increased gun port
2. Altered position of optical devices

2. Trials of robustness and precision.

The factory proving grounds tested the robustness of the gun mount using 171 increased power testing shots. Before trials, the mount was disassembled and measured. The recoil was within the limits of 560-580 mm. During firing, samples of gas concentration in the driver's compartment and fighting compartment were gathered. 

Additionally, the tank made 39 shots at targets at ranges of 600 and 1000 meters with shifts of fire at the Kopeisk proving grounds. The results of the shots are shown in the following table."

The following table does not list where the shots hit, but their time, range, and target are recorded. The tank can reload and fire in as little as 12 seconds, although the time is noticeably larger occasionally (when a target is reacquired, for instance). At 1000 meters, the tank shoots at a 5x5 meter target, at 600 meters, at a 1.25x1.25 meter target. 

"Note: during robustness trials, there were cases where the shell did not extract, which is explained by the use of old steel shells that have been re-loaded and the chamber being dirty.

All targets were hit directly. During gunnery trials, the tank drove 40 km over paved roads and 25 km off-road. The results of the trials are as follows:

1. The gun and mount system successfully passed robustness trials of 171 increased power shots. Measurements taken before and after trials have no difference between them, and are available in attachment 3.
2. The recoil mechanisms performed normally and passed trials (recoil remained within 560-580 mm). The pressure in the recoil brake was 27 atmospheres before trials, and 26.5 after.
3. The rate of fire is two rounds per minute.
4. The precision is good. Fire can be shifted quickly and without delay.
5. The elevation and turning mechanisms are comfortable to use.
6. The loader's position is cramped and makes his job difficult, but ensures the rate of fire of two shells per minute.
7. The ammunition rack is designed satisfactorily, aside from the following points:
1. The metallic cover should be replaced with a tarp.
2. Cut out the metal wall in the section covered by the tarp.
3. Increase the amount of shells in the turret bustle to 6 shells.
4. Bead form the metal to increase robustness.
8. The angle of depression is 2 degrees. It is desirable to increase it to 4 degrees.
9. The oscillating gun mantlet is not equal in thickness to the front of the turret, and some parts remain uncovered.
10. The frame cover is cast. It is necessary to use a stamped frame cover.
11. It is only possible to refill the brake fluid when the tank is tilted by 10 degrees or the recoil brake is removed.
12. The recoil brake pressure can only be checked when the gun is retracted by 300 mm. It is necessary to move the pressure valve.
13. There is no foot trigger.
14. Move the elevation indicator to the gunner's control panel.
15. Put a pear-shaped cushion on the periscope.
16. At high elevation, the elevation mechanism carrier can hit the gunner's guard plate. Make a slot in the plate.
17. Move back the sight 40-50 mm for more comfortable use.
18. Move the fault indicator, as it is covered by the machinegun.
19. The manual extractor is inconvenient; it slips off the shell rim.
20. Tighten the mount for the driver's mirror. There were two cases where is was shifted during fire.
21. The march stopper is reliable and allows to bring the gun into firing condition within 5-6 seconds.
22. The angles of deviation are not measured due to a lack of stock shots. The gun was fired using T-34 sights.
23. Move the DT machinegun up so that the disk magazine does not rub on the gun.
24. In order to find out the concentrations of gas in the tank, probes were taken after 30-40 shots with the engine off and hatches closed. The results are:
1. Fighting compartment: 0.201 mg/L
2. Driver's compartment: 0.308 mg/L
   With the engine on, the concentration is acceptable.

Penetration trials

On February 10th, factory #200 performed penetration trials using the U-11 122 mm tank howitzer and A-19 armour piercing shells. 

Trials conditions:

1. Shell mass: 24.6 kg (not entirely identical to stock)
2. The shells were fired at a stock cast KV turret (110-115 mm).
3. The distance between the muzzle and armour was 100 meters. The first load was 2100 grams of 9/7 powder and 0.030 of igniter. Muzzle velocity: 525.4 m/s. The shell penetrated the turret wall completely and remained behind the armour (see photo #1).
4. Second shot. Propellant charge: 2200 grams of of 9/7 powder and 0.030 of igniter. Muzzle velocity: 540.2 m/s. The shell punched out a plug and ricocheted (photo #2).
5. Third shot. Propellant charge: 2300 grams of 9/7 powder and 0.030 of igniter. Muzzle velocity: 546.4 m/s. Same results as the second shot (photo #3).
6. Fourth shot. Propellant charge: 2400 grams of 9/7 powder and 0.030 of igniter. Muzzle velocity: 573 m/s. Same result as the first shot.

Due to a lack of measuring equipment, the pressure in the barrel was not measured. It is necessary to discover the optimal amount of propellant at the Nizhniy Tagil proving grounds.

Conclusions:

1. The KV-9 tank passed trials and can be adopted into service with the Red Army.
2. When producing the KV-9, all aforementioned drawbacks must be corrected, with special care taken regarding the armour and ammunition rack.
3. As the 122 mm M-30 tank howitzer version passed trials, the commission deems it necessary to accelerate the mass production of the KV-9 tank.

February 16th, 1942"

CAMD RF 38-11355-668

KV-9 Production

"To the deputy People's Commissar of Tank Production of the USSR, Major-General of Technical Forces, comrade Kotin
Chair of the Technical Council of the Council of People's Commissars, comrade Satel
Director of the Kirov factory, comrade Mahonin
Director of Kalinin factory #8, comrade Fratkin
Regional GAU KA engineer at factory #8, Engineer-Colonel comrade Kasheyev
Regional GABTU BTU engineer at the Kirov factory, Engineer-Lieutenant-Colonel comrade Kozyrev

On the issue of a trial production run of KV-9 tanks.

Trials of the KV-9 tank armed with a 122 mm U-11 howitzer ended in March of this year.

In August of this year, continuing this work, factory #8 produced two U-11 howitzers with corrections according to proving grounds trials, and Kirov factory (#100) made corrections to the KV-9 tank according to the conclusions of the commission.

I ask for your orders to assemble a trial run of KV-9 tanks with U-11 howitzers for battlefield trials. For this, the following is necessary:

• Factory #8: produce a lightened pipe guard for all howitzers according to the blueprints provided to the Artkom and send them to the Kirov factory (Chelyabinsk).
• Factory #69: develop blueprints for scope markings for the TMFD and PT-4 sights for a gun with the ballistics of the U-11 122 mm howitzer, produce three of each, and immediately send them to the military representative at the Kirov factory (Chelyabinsk).
• Kirov factory: equip the fighting compartment in the old type of turret with a fighting compartment, ammunition rack, a commander's cupola of the KV-1S type (forward and to the right). In order to lighten the tank to 45 tons, mount the turret on a lighter KV-1S hull.

I ask you to inform me of your orders and estimated completion times.

Deputy GAU KA Chief and Artkom Chair, Major-General of Artillery, Hohlov

Deputy GABTU KA Chief, Major-General of Tank Forces, Korobkov

October 23rd, 1942"

CAMD RF 81-12038-32

Soviet Medium Tank Destroyers

Way back in the summer of 1940, engineers were already trying to fit an 85 mm gun into a T-34. Two T-34 hulls were shipped to factory #8 for this project. The easiest way to do this was to put it in a brand new open topped turret. The project stalled, but was revived in November of 1941. It was then that the project received the index U-20.

The U-20 consisted of a 52-K 85 mm AA gun on a mount from the M-30 122 mm gun. Three crew members occupied the turret, much like in the later T-34-85. The turret armour was not very thick, 45 mm in the front, and 20 mm on the sides. The TD carried 76 rounds of ammunition, 20 rounds in a ready-rack in the turret. The height of the vehicle was 2790 mm. In April of 1942, GAU decided not to build a U-20.

CAMD RF 81-12038-90

A more compact version of the U-20, the U-20-II, was developed in parallel.

The U-20-II had much more armour compared to the U-20, 75 mm in the front and 40 mm on the sides. The tank was shortened to 2475 mm in height, at the cost of a smaller 60 round ammo rack. The project met the same fate as the U-20, scrapped in April of 1942.

CAMD RF 81-12038-90

Another curious project on the T-34 chassis was the SU-2-122, ordered in December of 1942. Like with the SU-122 that everyone is familiar with at this point, the project was based on the T-34 chassis and was meant to provide indirect fire with 122 mm shells. However, instead of one M-30 howitzer, it had two.

CAMD RF 81-12063-13

The two guns would be capable of firing simultaneously. The mass of the tank was 35 tons, and resulted in having to lengthen the T-34 hull by one road wheel, bringing to total up to six. The project was cancelled before being built.

Speaking of the SU-122, here's a predecessor project, the ZIK-10, combining a U-11 howitzer and the T-34 hull.

Moving on to more projects on the SU-85 hull, the 85 mm gun was deemed to be less than what the platform could handle. The A-19 gun, that has already proven itself in combat with the enemy, was fitted into the unmodified casemate, resulting in a project called SU-D25. A similar project, the SU-D15, was armed with a 152 mm D-15 howitzer. 

SU-D25 (top) and SU-D15 (bottom). Retrieved from Solyankin et al, Soviet Medium SPGs 1941-1945