Friday, 30 May 2014

NII-48 Experiments, 1946

"Include the following topics in the research work for 1946:
  1. Production tanks and SPGs:
    1. Develop armour types for:
      1. Light and medium tanks and SPGs, capable of resisting 75 and 88 mm guns with the muzzle velocity of 1000 m/s.
      2. For heavy tanks and SPGs, capable of resisting 88 mm guns with the muzzle velocity of 1000 m/s and 122 mm guns with the muzzle velocity of 800 m/s.
    2. Improve the hull and turret of the IS-3 tank:
      1. Hull:
        1. Improve the connection between mudflaps and tank side.
        2. Increase the robustness of the rear of the hull.
        3. Increase the perpendicular robustness of the hull.
        4. Increase hull floor strength.
        5. Increase the hull roof strength.
      2. Turret:
        1. Develop reliable protection against 88 mm shells with the muzzle velocity of 1000 m/s.
        2. Improve the robustness of the gun mount.
        3. Strengthen the top of the turret.
        4. Develop a method of protecting the turret ring from shells.
      3. Put KDLVT brand steel into production for IS-3 tanks.
  2. Prototypes:
    1. T-54 tank
      1. Determine the armour that will protect the hull and turret from 75 mm and 88 mm shells with the muzzle velocity of 1000 m/s.
      2. Improve the shape of the hull from the point of view of robustness and shell resistance.
      3. Improve the armour of the turret to the point that it resists shells as well as the front of the hull.
      4. Develop armour screens for the T-54 to protect it from HEAT shells up to 105 mm in caliber inclusive and Faust type anti-tank rockets.
      5. Develop a robust track and track pin (increase track life to 3000 km).
      6. Investigate the optimal location for ammunition in the tank.
    2. 701 tank
      1. Determine the type of turret and hull armour that would will protect the hull and turret from 88 mm shells with the muzzle velocity of 1000 m/s and 122 mm shells with the muzzle velocity of 800 m/s.
      2. Remove all weak spots revealed during gunnery trials of the 701 hull.
      3. Improve the armour of the turret to the point that it resists shells as well as the front of the hull.
      4. Develop armour screens for the 701 tank to protect it from HEAT shells up to 105 mm in caliber inclusive and Faust type anti-tank rockets.
      5. Develop a robust track and track pin (increase track life to 3000 km).
  3. Experimental work:
    1. Complete research on tank armour up to [illegible] thick. Compare the resistance of heterogeneous and homogeneous armour to 75, 88, 122, 105 and 128 mm shells at angles of 0 degrees, 30 degrees, 45 degrees, and 60 degrees.
    2. Develop rolled and cast armour that can protect from the following shells
      88 mm at 1000 m/s
      105 mm at 900 m/s
      122 mm at 800 m/s
      122 mm at 1000 m/s
      128 mm at 900 m/s
      128 mm at 1100 m/s
      1. Homogeneous
      2. Cemented
      3. Surface hardened with high frequency current
      4. New design
    3. Develop methods of connecting tank armour up to 300 mm thick.
    4. Develop methods of protecting tanks from Panzerfausts, HEAT shells, and grenades. Test these methods on medium and heavy tanks.
    5. Develop methods of protecting the floor of tanks and SPGs from anti-tank mines.
    6. Develop automatic welding with austenitic electrodes. 
    7. Develop new types of austenitic electrodes that do not cause cracks in metal when welding.
    8. Develop a quenching technology that will prevent cracks on highly hardened armour.
    9. Develop steel for tank and SPG suspensions and design components to be resistant to HE and HEAT shells.
    10. Develop identical technical requirements for non-armoured tank and SPG components.
    11. Develop a unified method for controlling suspension raw materials.
    12. Develop instructions for welding tank and SPG hulls.
    13. Revisit the technical requirements for development and testing of armour during peace time.
    14. Process the materials on armour and tank metallurgy retrieved from Germany and present a report with conclusions and recommendations."

A few notes on this document. "Tank 701" is more commonly known as "Object 701", and eventually became the IS-4. Also, fans of comparing gun penetrations may skim over this document, but they should not. While this document doesn't mention any numbers, it mentions the protection from the 88 mm gun with the muzzle velocity of 1000 m/s (88L/71 KwK 43 in the Tiger II) as a requirement for light (what a lofty goal!) and medium vehicles, but protection from the 122 mm D-25 is already in the domain of the heavies. What a future-proofed gun the D-25 was! 


  1. "Develop reliable protection against 88 mm shells with the muzzle velocity of 1000 m/s."
    Does this mean that the 122 mm guns with the muzzle velocity of 800 m/s had less penetration then the 88mm´s against the turret of the IS-3?

    1. The early turret could be penetrated by both.

  2. The varying requirements are to be explained. The 88mm KWK43 -of course- has superior penetration against vertical plates -if used in connection with hardened, capped (german) AP ammunition.

    The 122mm gun had superior armour penetration to the 88mm -presumed that both use russian type of soft AP ammunition, which was not robust enough to withstand the high impact velocities, required to demonstrate the 1000m/s advantage.

    What the document does state is calibre and muzzle velocity, but not the ammunition type. In a theoretical exercise, baed upon the russian, uncapped AP-shot, the lower velocity 122mm offers more performance.

    1. The D-25 penetrates more in every practical scenario:

    2. The D25 has apparently better penetration when striking at lower terminal velocity, or against highly sloped armour -as could be expected- where the inferiority of the projectile to suffer break up / deformation is negated.

      Break up may even enhance high obliquity penetration, depending on the conditions.

      What has been failed to take into account is that at high velocities, as I mentioned above, the inferiority of the projectile comes into play again. The KWK 43 not only perforated the TIGER2´s turret face but also the back of the turret -a feature which the 122mm failed to achieve.

      Similarely, in US prooving ground trials 8 1/16" RHA provided complete ballistic protection (no crack through) vs 122mm A19´s muzzle velocity using soviet blunt APBC penetrators while the same 8 1/16" RHA was easily penetrated by the KWK43 88mm PzGr 39 under identic test conditions not only at muzzle velocity but also at lower striking velocities corresponding to ranges >600 m. The Army ballistic limit (crack through) was aprox. 2735fps (correponding to 1700m), while the Navy Ballistic limit (complete penetration) was 3081 fps (corresponding to 8" penetration at 0° and 600m).

      8" fully protects vs 122mm at 0m
      8" starts to fail vs 88mm KWK43 at 1700m -protection limit presumably >2000m

      That´s the most severe impact condition in terms of rapidly applied shock to the projectile, and the 122mm is at disadvantage in this specific case.
      This doesn´t surprise me considering the poor steel mix and lack of hardening treatment applied on soviet ww2 ammunition.

      At long range, and lower impact shock, when the projectile stays intact, the 122mm showed what everybody expects: A noticable performance edge over the 88mm.

      The 88mm broke up striking >45° obliquity more often than not and beyond this obliquity, both projectile suffered break up, handing advantage back to the 122mm.

    3. The tests I linked to start at 200 meters. That's plenty fast. Sure, the projectile might shatter at 0 meters, but when are you going to be firing the cannon at such a close range?

  3. The 122mm flat nosed APBC didn´t penetrate the IS3 glacis at 200m, it made a dent and broke up as evidenced by the pictures. The older, sharp tipped 122mm penetrated at 900m and slightly more perpendicular to the plate (55° instead of 60° compound obliquity), again at lower velocity corresponding to lower impact shock. But the hard armour might have helped additionally here (high hardness plate increases projectile normalization)
    However, these cases are high obliquity, much in excess of 45° and neither soviet nor german projectile could be expected to stay intact.

    To close the circle, failure at high impact velocity due to inferiority of projectile is a matter of significance. Particularely for the planned high velocity 107mm, 100mm and 122mm guns. But alo when comparisons are made based upon calculation from one party or the other (each considers the other to have projectiles of similar properties to the own, of which they at least know the performance)
    The ww2 period soviet guns were well advised to have a larger calibre and lower muzzle velocity due to the self imposed projectile limitations.

    The high velocity gun projects from 1940 to 1945 failed partly because the progress in muzzle energy wasn´t accompanied by a similar progress in projectile quality.

    The 100mm gun, f.e. required a change from Br-412B APBC to Br-412D APCBC projectiles post war (service 1953?) to allow the full performance spectrum of the gun system to be exploited. The Br-412D is, You may know, a projectile inheriting a lot from the late ww2 german PzGr39 APCBC design charakteristics (lack of typical soviet projectile grooves, added armour piercing cap, low crh nose and secant ogive ballistic cap, -don´t know the steel mix and hardening layout).

    However, the same limitations beset the german AP until later in 1941. All their army projectiles broke up striking at high velocity. The uncapped 5cm PzGr Gg o.K. in service back then, f.e. was expected to perforate reliably 52mm RHA at 30° and 580m/s. Raising the striking velocity didn´t improve performance: 56mm RHA at 850m/s due to projectile break up.
    The improved capped 5cm PzGr39 Gg. perforated only 48mm RHA at 30° (the cap degrades performance if the projectile stayes intact anyways) and 580m/s but 58mm RHA at 700m/s and 78mm RHA at 30° and 850m/s -the cap protected the projectile.

    The virtually indestructible projectiles developed in the period 1939 to 1940 (out of necessarity to deal with thicker armoured french and british infantery tanks and later, soviet tanks) were the only reason why the 50mm, 88mm and 75mm long barreled guns mid war were perceived as powerful.

    This is case of a very significant interaction between projectile and gun system.

    1. Sure, it didn't penetrate the glacis from 200 m, but neither did the KwK 43. There is no range in any of the tests where its alleged superior penetration is realized.

      Also if you look at the BL-9 and BL-10 articles, the high velocity cannons were perfectly fine at punching through thick plate.

  4. I don´t see sufficient indication suggesting that these interpretations can be readily extracted from the aviable sources.

    You asked that there is no range that the KWK 43 realizes superior penetration. This is partly attributable to the fact that the conditions where those exist were not tested for in the samples published hitherto. Soviet comparative high impact velocity trials never compare soviet with german projectiles for a reason.
    However, the cases do exist even in the published material:
    The KWK 43 beats the 122mm D25T in perforation of thick plate in Aberdeen under controlled and quantifyable conditions.

    It also beats it against 180mm KT turret front from a rather problematic test case in Kubinka (by also penetrating the 80mm spaced back, 180mm + 80mm RHA acc. to De Marre formula for spaced nickel steel plates is the aequivalent of > 220mm single layer thickness). The 122mm being unable to punch through the FERDINANDs nose front armour while even 75mm PzGr39 did so is another case.

    Closing the distance doesn´t help the 122mm because unlike PzGr39, the untempered 35 HGS grade steel Army AP shot will suffer degrading deformation at higher velocities, greatly reducing the effective performance. A case can be made that the absolute penetration is expected to plateau or even reduce because of the effect (NVA penetration tables using german 5 out of 5 successes defintions grant the 122mm D25T a penetration of 160mm RHA vertical plate at 100m, though it´s not clear to me whether or not these tabulations were calculated based upon close or long range test data). More data is necessary to assess this question in detail but I do not doubt for a minute that You will find these issues exposed if You look for them.

    You raised the point that the high velocity BL-9 and BL-10 were capable of punching through thick armour but the data presented here show a different picture.
    First of all, we don´t know the type of projectile used in these trials.

    Then, the 1000m/s mv BL-9 failed to penetrate 203mm armour at 1000m at 90° in seven out of eight shots (3 x dented, 4 x stuck in plate, 1 x through), where velocity is high enough for projectile damage. The reliable penetration is probably not much better than the D25T and at around 180mm despite a masssive raise in striking energy. That gives a massive edge in long range penetration but short range penetration (except against highly sloped armour where break up affects all projectiles similarely)of such a powerful gun system is best described as disappointing by a critical observer.

    In comparison, the AP-performance of BL-9 with domestic AP shot is noticably worse than the KWK 43 with PzGr 39 which reliably penetrated at about the same or lower absolute striking velocity 8" RHA vertical (see Aberdeen trials or Hillersleben minutes).

    That doesn´t mean that soviets were unable to master high performance AP-shot, Russia had a track record of developing excellent Navy APC since after the RJW.
    The SU was not prepared to accept the larger economic costs of applying different types of steel, tempering treatment and projectile cap fabrication for mass produced AP shells, which is why their large calibre Army AP regularely broke up striking about 1,3 cal RHA at velocities where an intact projectile would penetrate.

    Most people discussing these issues will be surprised how soft these AP were: The hardness of a late ww2 period BR-471B 122mm APBC varied between 110 BHN and 118 BHN and was homogenious from nose to base. Tests with captured 76.2mm AP projectiles in Unterlüß saw them literally mushroom against a vertical plate 1.5 cal thick.
    PzGr 39 series re-engineered 76.2mm APCBC had a nose hardness of 600BHN, dropping inversely progressively from nose to bottom and reaching BHN 245-275 at the base. They penetrated up to 2.5 cal vertical RHA plate at elevated velocity and stayed intact.

    1. >The 122mm being unable to punch through the FERDINANDs nose front armour while even 75mm PzGr39 did so is another case.

      Why are you comparing APCR and regular AP?


  5. The 75mm APCBC did not penetrate the upper frontal hull (a 200mm solid RHA plate inclined a bit) -that´s where the APCR did made it through.

    However, I refer to regular 75mm APCBC, in Your article "75 BR" [in kyrillic]. There were two clean penetrations through the 100mm + 100mm frontal hull by 75mm L70. One with PzGr 39 APCBC, another with Pgr 42 "Hartkern" APCR. The latter made a smaller hole in the plate´s back, as could be expected.

    Altough this hull section was nominally also 200mm thick like the superstructure front, the actual resistence was a bit smaller, and equalled more like 180-185mm according to the formula used for laminated RHA developed by Okun. This was narrowly within the capability of reliable 75mm APCBC penetration.

    While both, the 75mm PzGr 39 and -42 went entirely through this ca. 182mm effective plate, the 122mm AP penetrated at the weakened upper plate edge (roughly half of the plate touched by the projectile) only into the first plate, and ricochetted off, failing to make a hole at velocities equalling 1400m.
    This was at velocity where shell break up of the 122mm typically isn´t yet a dominant factor. The hit is just above two holes, indicating an already stressed plate by previous impact (shock embrittelment has to be reckoned with).