Sunday, 16 March 2014

Soviet Medium Tank Destroyers Part 2

You've read about Soviet experimental medium SPGs, but now here's some more exciting content from CAMD RF 38-11369-1, in the vein of the light SPG article.

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Production vehicle, SPG SU-122, produced by the Ural Machine Building Factory of the NKTP

According to GOKO decrees in October-December 1942, the Uralmash factory designed and built an experimental prototype of the SU-122 SPG. The SU-122 consists of a 122 mm M-30 howitzer on the T-34 hull. 

From December 5th to December 19th of 1942, the SPG underwent trials at the Gorohovets proving grounds, over 430 km and 281 shots. The commission concluded that the SPG passed trials. GOKO decree #2559 on December 2nd, 1942, adopted the SU-122 SPG into the Red Army.

Experimental work on medium SPGs

1. On the SU-122M

The Uralmash factory, on its own initiative, developed a modernized SU-122M SPG. This vehicle was based on the SU-122 SPG trials, overseen by Major-General of the Tank Engineering Forces, comrade Ogurtsov.

The modernization was as follows:
  1. Installation of a new D-11 122 mm howitzer instead of the M-30 122 mm howitzer.
  2. Increase of the fighting compartment width by 350 mm and height by 100 mm.
  3. Inclusion of a telescopic sight for direct fire.
  4. Improved fuel and control systems.
In June of 1943, the SU-122M underwent trials at the Ural proving grounds over 329 shots and 859 km. The experimental prototype passed trials, but was not adopted by the Red Army, as a decision was already made to produce SU-85 SPGs that used 85 mm guns with improved anti-tank capability.

Experimental prototype of the modernized SU-122M SPG designed by the Ural Machine Building Factory of the NKTP
  1. Combat weight: 31.43 tons
  2. Crew: 4
  3. Gun: 122 mm M-30 howitzer
  4. Muzzle velocity: 515 m/s
  5. Horizontal traverse: 20 degrees
  6. Vertical traverse: -3 degrees to 26 degrees 30 minutes
  7. 122 mm shells: 40
  8. Front armour thickness: 45 mm
  9. Maximum speed: 55 kph
  10. Average speed: 35 kph
  11. Average off-road speed: 20 kph
  12. Engine: V2-34
  13. Maximum engine power: 450 hp
  14. Fuel tank capacity: 460 L

2. On the SU-85

According to GKO decree #3289 from May 5th, 1943, the Uralmash factory developed and produced experimental SPGs in May-July of 1943.
  1. SU-85-I, with a TsAKB S-18-1 85 mm gun
  2. SU-85-II, with a factory #9 D5-S85 85 gun
  3. SU-85-IV with a TsAKB S-18 85 mm gun
All of these SPGs were based on the SU-122 SPG. Over the period from July 25th to August 6th of 1943, all three SPGs underwent trials at the Gorohovets proving grounds over 500 km and 300 shots. A commission headed by Lieutenant-General of Artillery comrade Taranovich (today Colonel-General of Artillery). The D5-85S gun designed by factory #9 achieved superior results in trials.

Marshal of the Armoured Forces, comrade Fedorenko, Marshal of Artillery, comrade Yakovlev, and the People's Commissar of Tank Production comrade Malyshev visited the proving grounds in early August 1943, and agreed to the adoption of the SU-85 armed with a D5-85S gun, of which they informed comrade Stalin over the phone.

After this, Uralmash began mass production of SU-85 SPGs.

In September of 1943, Colonel-General of Tank Forces, comrade Biryukov visited the factory. According to an assignment from GOKO, he inspected the production lines, and occasionally offered help and coordination of factory #9 and Uralmash to aid in quantitative and qualitative improvements in production of the SU-85.

By his orders, one of the production SPGs was subjected to mobility and gunnery trials. The trials were conducted by Engineer-Lieutenant-Colonel Kovalev.

The tactical-technical characteristics of the SU-85 SPG were confirmed by GOKO decree #4436 on October 27th, 1943, provided to NKO (comrade Fedorenko) and NKTP (comrade Malyshev). With this new SPG, the Red Army received its first medium tank destroyer, capable of fighting new enemy tanks.

Experimental prototype of the SU-85 SPG designed by the Ural Machine Building Factory of the NKTP
  1. Combat weight: 29.15 tons
  2. Crew: 4
  3. Front, side, and rear armour: 45 mm
  4. Gun: 85 mm D5-S85
  5. Muzzle velocity: 792 m/s
  6. Horizontal traverse: 20 degrees
  7. Vertical traverse: -4 to +25 degrees
  8. 85 mm shells: 48
  9. Maximum speed: 55 kph
  10. Average speed: 35 kph
  11. Average off-road speed: 20 kph
  12. Engine: V2-34
  13. Maximum power at 1700 RPM: 450 hp
  14. Fuel: diesel
  15. Fuel capacity: 460 L
3. On the SU-100 SPG

Following GOKO decree #481 from December 27th, 1943, Uralmash developed and produced two SU-100 prototypes in March-May of 1944, one with a 100 mm D-10S gun designed by factory #9, and one with a 100 mm S-34 gun, designed by TsAKB. The SU-100 was based on the SU-85.

Several changes were made to the old SPG to increase its combat ability:
  1. As requested by USA GBTU, the front armour was increased. Instead of the 45 mm armour of the SU-85, the armour of the SU-100 was 75 mm, at the same angle.
  2. Robustness of the front road wheels was increased.
  3. Ventilation was improved.
  4. Gearbox was improved.
Other changes were made, 15 in total. The SU-100 prototypes were tested twice. First trials of the SU-100 with the D-10S gun were carried out by a commission headed by Colonel Rupyshev at the Gorohovets proving grounds from March 9th to March 27th, 1944. The trials lasted 564 km and 1040 shots. The SPG passed these trials. However, the commission requested that some design defects be corrected before entering production.

Secondary trials were performed by the same commission at the Gorohovets proving grounds from June 24th to July 6th, 1944. 

The SU-100 prototype with the S-34 gun underwent trials. Trials were done in comparison with the SU-100 with the D-10S SPG. The SU-100 with the S-34 gun was trialled over 877 shots and 250 km, and did not pass trials. Work on this SPG concluded, as the SU-100 with the D-10S gun was more promising.

The D-10S prototype, after being corrected after March trials, was tested simultaneously. The SPG passed trials over 923 shots and 250 km, and was recommended for adoption by the Red Army.

Comrades Colonel Rypushev and Engineer-Majors Konev and Volgushev performed exemplary work during design and trials of the SPG.

GOKO decree #6131 from July 3rd, 1944, accepted the SU-100 for mass production and use by the Red Army.


    Experimental prototype of the SU-100 SPG designed by the Ural Machine Building Factory of the NKTP
    1. Combat weight: 31.6 tons
    2. Crew: 4
    3. Front armour: 45-75 mm
    4. Side and rear armour: 45 mm
    5. Gun: 100 mm D-10S
    6. Muzzle velocity: 900 m/s
    7. Horizontal traverse: 16 degrees
    8. Vertical traverse: -3 to +20 degrees
    9. 100 mm shells: 33
    10. Maximum speed: 50 kph
    11. Average speed: 30 kph
    12. Average off-road speed: 18-20 kph
    13. Engine: V2-34
    14. Maximum power at 1700 RPM: 450 hp
    15. Fuel: diesel
    16. Fuel capacity: 460 L
    4. On the SU-122P SPG

    In the end of 1943, Uralmash, on its own initiative with approval from USA GABTU, began work on equipping the SU-85 with a 122 mm gun. This work was conducted with the goal of exploring the viability of 122 mm guns on medium SPGs.

    In June of 1944, a prototype was produced, indexed SU-122P. This prototype differed from the SU-100 experimental prototype only in armament. The SU-122P SPG was armed with a 122 mm D-25S gun.

    In November 1944-February 1945, the SU-122P prototype was tested on the NIBT proving grounds over 1000 km, and fired 258 shots at the Leningrad proving grounds.

    The pause between the prototype being ready and trials beginning can be explained by Uralmash being occupied with work on the SU-100, and did not submit the SU-122P for proving grounds trials.

    Mobility and gunnery trials showed that armament of medium SPGs with a 122 mm D-25S gun is possible.

    USA GBTU decided that an SPG with a rear fighting compartment be developed for this gun, as placing a 122 mm gun in a SU-85 (SU-100) SPG does not result in a comfortable placement of crew and ammunition. Work on the SU-122P ceased.

    Experimental  prototype of the SU-122P SPG designed by the Ural Machine Building Factory of the NKTP
    1. Combat weight: 31.5-32 tons
    2. Crew: 4
    3. Front armour: 45-75 mm
    4. Side and rear armour: 45 mm
    5. Gun: 122 mm D-25S
    6. Muzzle velocity: 781 m/s
    7. Horizontal traverse: 16 degrees
    8. Vertical traverse: -3 to +17 degrees
    9. 100 mm shells: 26
    10. Maximum speed: 50 kph
    11. Average speed: 30 kph
    12. Average off-road speed: 18-20 kph
    13. Engine: V2-34
    14. Maximum power at 1700 RPM: 450 hp
    15. Fuel: diesel
    16. Fuel capacity: 400 L
    5. On the SU-85PM SPG

    The experimental SU-85PM SPG was produced at Uralmash on its own initiative in August-December of 1943. This SPG was composed of a production SU-85 equipped with an increased power D5-S85PM gun, designed by factory #9. Due to a longer barrel and increased density of propellant, the muzzle velocity increased to 900 m/s, as opposed to 800 m/s of the stock gun.

    The SPG was trialled in January-February of 1944 at the Gorohovets proving grounds, firing 755 shots. The SPG passed trials, but due to the installation of a D-10S gun, which was significantly more powerful than the D5-S85PM gun, the need for the latter disappeared.

    Experimental prototype of the SU-85PM SPG designed by the Ural Machine Building Factory
    1. Combat weight: 29.5 tons
    2. Crew: 4
    3. Front, side, and rear armour: 45 mm
    4. Gun: 85 mm D5-S85PM
    5. Muzzle velocity: 900 m/s
    6. Horizontal traverse: 20 degrees
    7. Vertical traverse: -3 degrees 20 minutes to +26 degrees
    8. 85 mm shells: 48
    9. Maximum speed: 55 kph
    10. Average speed: 30 kph
    11. Average off-road speed: 18 kph
    12. Engine: V2-34
    13. Maximum power at 1700 RPM: 450 hp
    14. Fuel: diesel
    15. Fuel capacity: 460 L
    6. On the SU-101 and SU-102 SPGs

    Following the order of GBTU, Uralmash designed two experimental SPGs with rear fighting compartments in March of 1945. The prototypes differed in armament.
    • The SU-101 SPG was equipped with the D-10S 100 mm gun.
    • The SU-102 SPG was equipped with the D-25S 122 mm gun.
    At the end of April 1945, Uralmash produced the first SU-101 SPG. After 76 km of trials, design defects became apparent. The driver's compartment rapidly heated to 50-60 degrees, making it impossible for the driver to work. Other defects were also discovered.

    Gunnery trials showed weakness of attachment of armoured plates, as well as insufficient robustness of some plates.

    Currently, Uralmash is improving the design of these SPGs. All changes are being made to the second prototype with the D-25S gun. Factory trials are scheduled for the end of June of 1945.

    The new SU-102 prototype differs from the SU-100 in the following way:
    1. New engine and new layout of components.
    2. Increased armour of the fighting compartment and hull.
    3. Increased power of the gun and machineguns.
    4. Improved performance over horizontal obstacles (trenches) and movement on forest roads due to gun position.
    The production of these experimental SPGs is a step forward in the development of medium SPGs, but the SU-101 and SU-102 no longer meet modern requirements for armament, armour, and transmission design.

    The new medium SPG prototypes, in addition to removal of currently known defects, require subsequent improvement in all main design criteria.

    Experimental medium SPG with rear fighting compartment.

    Tactical-technical characteristics of the SU-101 and SU-102 SPGs
    1. Combat weight: 33-33.5 tons
    2. Crew: 4
    3. Ground pressure: 0.84-0.85 kg/cm^2
    4. Length with gun: 6850-7000 mm
    5. Width: 3070 mm
    6. Height: 2200 mm
    7. Clearance: 430 mm
    8. Front hull armour: 90 mm
    9. Front fighting compartment armour: 120 mm
    10. Side fighting compartment armour: 90-75 mm
    11. Rear armour: 40 mm
    12. Gun: 100 mm D-10S or 122 mm D-25S
    13. Muzzle velocity: 900 (D-10S) or 781 (D-25S) m/s
    14. Horizontal traverse: 20 degrees
    15. Vertical traverse: -4 to +20 degrees
    16. Sights: TSh-19 or TSh-17
    17. 122 mm shells: 28
    18. 100 mm shells: 36
    19. Maximum speed: ~50 kph
    20. Range (highway): 250-300 km
    21. Range (off-road): 150-200 km
    22. Engine: V2-44
    23. Maximum power: 500 hp
    24. Fuel: diesel
    25. Fuel capacity: 440 L"

    3 comments:

    1. D5-S85PM:
      Is that supposed to be the "BM"?

      And does anyone know why the BM gun was never even considered for a tank (say T-44 - that could *just* cram a 100mm gun so surely a 85mm enhanced power gun would have given it a bit more bite without needing quite as much space)?

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      Replies
      1. It was PM in the document. Based on the muzzle velocity, it looks like they're referring to the D-5SBM gun anyway.

        SPGs are easier to mount experimental guns on. If the BM guns went anywhere, they would probably be installed on tank as well.

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    2. Huh, I did wonder about the SU-101 driver compartement. Looks pretty cramped and with (I assume) the main engine space right behind and the radiator to the right of it... can't say I'm surprised it became an impromptu sauna.

      ReplyDelete