Monday, 3 June 2019

Big Guns

"To the Chief of the 16th Department of the GAU Artillery Committee, Colonel comrade Zhevanik

I report on the work that I performed during my trip to Sverdlovsk and Chelyabinsk from May 3rd to May 28th, 1943.

1. Kalinin factory #8.

Based on directions by Lieutenant General of Artillery Hohlov, I organized work to design and produce an experimental 85 mm tank gun. To achieve this, I supplied factory #8 with a copy of the tactical-technical requirements and necessary blueprints with the aid of the GAU military representative at factory #9. I negotiated with the factory's director, comrade Fratkin, as well as the chief engineer and chief designer. Based on this meeting, comrade Fratkin gave the order on May 4th to quickly begin work on designing the gun with the aim of completing blueprints by May 10th.

The deadline for production and installation in a tank was set at May 20th, 1943, under the condition that the GAU and NKV Technical Council give factory #8 the contract. Having informed you of this decision and received a promise to confirm the order by ciphertext, I connected the Kirov factory (Major General comrade Kotin) and factory #8 (comrade Fratkin). Comrade Kotin made the decision to produce a turret at the same time as factory #8 was working. To achieve this, Kotin drove with three tanks (2 IS and 1 KV-1S) and a brigade of designers (9), with two oscillating parts of the ZIS-5 gun to make work faster.

Work was fully underway by May 8th, however the NKV (comrade Ryabikov) prohibited comrade Fratkin from producing a prototype, and a ciphertext confirming the meeting results from Moscow never came. On May 10th, after the blueprints were completed and details of its installation in the turret were confirmed, the work at factory #8 ended.

On the factory #8 project, one can say the following:
  1. The design of the gun allows a painless transition to more powerful ballistics (muzzle velocity of 930-960 m/s, maximum pressure of 3000-3100 kg/cm²).
  2. The barrel group is the same as the one on the 85 mm AA gun, but a new rigid rod type of semiautomatic mechanism was developed that can be used on the tank or the AA gun.
  3. Considering the difficulty with the casting plants of the Ural industrial zone, the tank gun was a stamped cradle used on the F-34, which is already mastered by factory #9.
Factory #8 will send the project materials to the ArtKom, but only upon receiving an official request.

2. Factory #9.

Factory director comrade Gonor refused to perform the design work on May 3rd (my day of arrival at Sverdlovsk), as his goal was to further develop 122-152 mm howitzers. However, after the publication of GOKO decree #3289ss on May 5th, comrade Gonor assembled a meeting where it was decided to begin design work according to the tactical-technical requirements issued by the ArtKom in March-April of this year.

The following prototypes were announced:
  • D-5 85 mm SPG gun, now called D5-S-85
  • D-6 122 mm SPG howitzer, now called D5-S-122
  • D-7 85 mm tank gun, now called D5-T-85
  • D-8 122 mm tank gun, now called D5-T-122
Tank guns differ from SPG ones only in the additional mount for a machinegun.

The design of the M-30 howitzer is the basis of all the guns, which led to the unification of all threads, diameter of openings, etc.

On May 22nd, the last day of my visit, working blueprints of all main parts were delivered to  manufacturing and the target date for completing all blueprints was May 25th. Prototypes were expected to be completed by June 15th.

The SPG gun projects were very satisfactory to the Uralmash factory. The design bureaus of both factories work well together. The 85 mm caliber tank gun design was not coordinated with the Kirov factory, but there is still the possibility of installing it into the IS or KV-1S tank.

The advantage of factory #9's designs is that they can most easily be introduced into mass production. With only one type of gun, we can obtain 4 different guns by replacing the barrel, recoil mechanism, and breech.

The 122 mm howitzer breech can easily allow for transition to a 1/4 automatic sliding breech. Design and production of the sliding breech is postponed due to tight deadlines.

3. Uralmash factory

I familiarized myself with and even participated in factory trials of a modernized 122 mm SPG. It is necessary to mention the drawbacks of the SU-122M:
  1. Heavy weight (31.5 tons).
  2. Insufficient visibility.
  3. The screw breech rests on the commander's knees at an elevation angle of 5 degrees.
  4. The design of the gun mantlet is unfinished.
I did some consulting work regarding the design of an 85 mm SPG and took all measures to unite the work of factory #9's design bureau and Uralmash.

The decision of factory director comrade Muzrukov was to develop and produce the following prototypes:
  1. 85 mm SPG on the SU-122 chassis (TsAKB gun).
  2. 85 mm SPG on the SU-122M chassis (TsAKB gun).
  3. 85 mm SPG on the SU-122 chassis (factory #9 D-5 gun).
  4. 122 mm SPG on the SU-122 chassis with a horizontal ammunition rack (factory #9 D-6 gun).
Production of the prototypes is performed according to the director's order #23s issued on May 18th of this year.

Uralmash factory is due to receive TsAKB prototypes in priority order.

Speaking of TsAKB prototypes for the SPG, it is worth mentioning that the cradle needs to be changed. The unaltered ZIS-5 cradle is unsuitable for an SPG due to its width, which means that the front armour would have to be weakened (large opening cut).

4. Kirov factory

We agreed to produce an experimental prototype of an A-19 gun on a SU-152 chassis. The decision was formalized in the minutes. The factory agreed to:
  1. Complete the blueprints and send them to the ArtKom by May 31st.
  2. Produce a prototype and install the gun in an existing chassis by June 15th.
  3. Perform trials jointly with the ArtKom during the period of June 15-20th, gathering sufficient data for the marking of sight scales and composing technical requirements.
I inspected the blueprints of the altered SU-152 fighting compartment made after the commission made its recommendations. The hull was not widened, as that would have increased the mass of the SPG greatly. The ammunition rack and fuel system have been changed to meet the commission's requirements. 

After the trials of the A-19 system, the same hull will be used to test the new ammunition rack and fuel system and be tested by July 5th. Trials will be performed in the amount of one full fuel tank's march and firing of 40 rounds to measure the rate of fire and ease of loading.

Considering that production of IS tanks is coming and the KV-1S will be phased out, the factory prepared two variants of a SU-152 on the IS chassis. Both variants were examined by me and deemed insufficiently satisfactory. A decision was made to develop a third variant. Direction for the work has been given.

The deadlines for this project are: design work finished by July 5th, wooden model completed by July 15th. The decision was formalized in the meeting minutes.

I negotiated with Major General comrade Kotin to develop open top SPGs on the KV or IS chassis mounting the Br-2, B-4, and Br-5 guns. There are already some drafts, but the factory needs:
  1. Tactical-technical requirements.
  2. Blueprints of the oscillating parts of the systems.
  3. Dimensional blueprints of the projectiles and propellant casings.
  4. Firing tables and service manuals.
The project work was done according to the conclusions of the ArtKom plenum dated April 14th, 1942.

Since urgent work on the IS tank will be complete in July-August, we can receive the technical projects of these SPG after that. SKB-2 (Major General Kotin) is very willing to perform this work.

Assistant to the Chief of the 16th Department, Engineer-Major Solomonov"

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