Monday 18 November 2013

Soviet Experimental SPGs

When the Red Army encountered Finnish defenses during the Winter War, they realized that they had no self propelled guns capable of defeating concrete fortifications. Using the chassis of the three new heavy tanks (SMK, T-100, and KV), new self propelled artillery projects were developed. The only one of them that really got anywhere was the KV-2. Various other projects, such as the 212 SPG (known to many more as Object 212) got somewhere before slowly dying due to a sudden lack of an enemy with fortifications they would be needed against.

CAMD RF 38-11355-101

"Act on the state of completion of the object #212 (SPG)

The current act is composed to state that the following work was performed on the experimental object #212 (SPG) as of May 29th, 1941.
  1. Sketches and technical project, costing 100,000 rubles.
  2. Working blueprints, costing 200,000 rubles.
  3. Armoured hull produced at the Izhor factory, costing 150,000 rubles.
The total cost of the work was 450,000 rubles, which is the sum that must be paid in advance to the project. The final cost will be computed using report calculations.

Lantzberg, Kotin, Rogachev, Shpitanov"

However, the project stalled way before May. The SPG has been sitting in that condition since March. Soon after this document was written, the war started, and the 212 was shuffled around from factory to factory, eventually disappearing forever. 

Work on a self propelled high caliber howitzer had to be put on hold, but the artillery officers never forgot about it. Eventually, the Artillery Committee ordered it back up and running. Item #12 on a list of projects at the Kirov factory (CAMD RF 38-11369-91) contains the following:

"203 mm self propelled B-4 howitzer on the chassis of a KV-1S tank. Kirov Factory and factory #172. Planned work for the Artillery Committee.

The Artillery Committee planning session from April 15th, 1942, identified the need for a self propelled Br-2 gun on the KV chassis. As a result of experience in the construction of self-propelled guns in 1942-1943, it was deemed possible to install a B-4 howitzer in a semi-enclosed SPG. The Kirov factory and factory #172
have a contract with Artkom's 16th department regarding this project. Each factory is developing the project separately."

The need for a Br-2 on a KV chassis appears even earlier, in a document from November of 1941 that lists SPG projects for 1942 (CAMD RF 81-12104-115).

In November of 1943, the GAU chief, Colonel Yakovlev, wrote a letter to the People's Commissar of Tank Manufacturing Malyshev:

"According to your announcement, the Commissariat of Tank Manufacturing intends to continue work on design and production of experimental self propelled 152 mm Br-2 and 203 mm B-4 guns, which was ordered by the GAU in 1940, but was interrupted in 1941 due to the start of the war.

The GAU considers this work to be necessary. The blueprints for the guns and ammunition have been sent to the Kirov Factory SKB-2 by GAU on June 19th of this year.

Orders to deliver a 152 mm Br-2 gun and 203 mm B-4 howitzer to factory #100 have been given.

The technical requirements, revised based on experience of the war, are currently being completed at GAU and will be sent to you in the coming days."

CAMD RF 81-12063-1

That desire was fulfilled in less than a year, in the form of the S-51 self-propelled howitzer. Unlike the previous designs, where the gun was fully enclosed, the S-51 mounted it on a mostly open platform, with a shield in the front that could flip up to protect the crew from shrapnel and bullets.

"An Order of the State Committee of Defense

On the question: manufacturing a party of 203 mm self propelled howitzers B4-S51

The Red Army accepts the 203 mm B4-S51 howitzer, developed by TsAKB NKV, consisting of the 203 mm B-4 field howitzer model 1931 on a KV-1S tank chassis.

NKTP (comrade Malyshev) and GURT of the Red Army (comrade Sosenkov) must deliver 50 repaired KV-1S tanks to NKV, without the rotating turret, and with an intact suspension, engine (with less than 10% of its lifetime hours expended), transmission, and spare parts by the following dates:
  • 25 units by August 10th
  • 25 units by August 25th
NKV (comrade Ustinov) must manufacture parts and organize mass production of 203 mm B4-S51 howitzers in the following time frame:
  • By August 20th: 20 self propelled howitzers
  • By August 30th: 30 self propelled howitzers
During mass production, remove the defects discovered during trials. TsAKB NKV (comrade Grabin) must edit the blueprints accordingly, and turn them in by August 1st to GAU of the Red Army."
CAMD RF 81-12038-413

CAMD RF 38-11369-287

"The 203 mm self propelled "S-51" howitzer built by the NKV TsAKB, consisting of a 203 mm model 1931 howitzer (B-4) on a turretless KV-1S tank with a foundation plate for the installation of the rotating part of the howitzer and slots cut in the roof of the hull for the recoil mechanisms underwent trials. The main technical-tactical characteristics of the self propelled S-51 howitzer are as follows:
  1. Ballistics
    1. Caliber: 203.2 mm
    2. Muzzle velocity: 607 m/s
    3. Maximum chamber pressure: 2366 kg/cm^2
    4. Shell mass: 100 kg
    5. Muzzle energy: 1900 ton-meters
    6. Maximum range: 18025 meters
  2. Combat
    1. Vertical range: 0-60 degrees
    2. Horizontal range: +/- 4 degrees
    3. Ammunition capacity: 12 rounds
    4. Rate of fire: 1-1.5 RPM
    5. Full combat weight (according to TsAKB data): 49.7 tons
    6. Crew: 10
    7. Maximum speed: 30 kph
  3. Design
    1. Bore axis height: 2793 mm
    2. Recoil length:
      1. Long (up to 16 degrees 30 minutes): 1200-1300 mm
      2. Short (from 16 degrees 30 minutes and up): 850-890 mm
    3. Initial pressure in return gear: 40+/-2 atmospheres."
In the meantime, GAU Artkom was developing their own 203 mm SPG at Perm (factory #172). The vehicle, indexed M-22, was very similar to the S-51: a SU-152 with the casemate removed, and B-4 howitzer added.

CAMD RF 38-11369-108

Thankfully, sane artillery projects were also being developed at the time, such as a SU-76 with a 122 mm howitzer, to make a more portable and cheaper SU-122. 

CAMD RF 38-11369-481

"May 1944
To the director of the Gorkiy Automotive Factory

I ask you to order the Construction Bureau to explore the possibility of installing a 122 mm howitzer in an SPG on the chassis of the SU-76.  In order to obtain the tactical-technical characteristics of the 122 mm howitzer, contact the Construction Bureau of the NKV factory #9 in Sverdlovsk. 
Report back on your decision and subsequent actions.

Chief of the GBTU KA
Lieutenant-General of the Tank Forces

The exact date of the above document was cut off in the scan, but seeing as how all the other stamps and signatures on it are from June, it was likely late May.

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