Monday, 22 August 2016

76 mm Regimental Gun Penetration

"To the People's Commissar of Defense, comrade I.V. Stalin.

I report that HEAT shells for the 76 mm mod. 1927  regimental cannon developed by the GAU Artkom on the basis of captured German shells were tried on May 23rd at the Sofrino proving grounds.

During trials against a 50 mm cemented plate, half of all fired shots resulted in complete penetrations with a diameter of 30 mm against both a flat plates and plates angled at 30 degrees.

This increases the armour piercing effect compared to the stock armour piercing shell of the 76 mm mod. 1927 regimental gun which, at a range of 200 meters, penetrates 32 mm and 28 mm of armour angled at 0 and 30 degrees respectively.

Considering the positive result of the trials and the simplicity of HEAT shells, I ask you to order the People's Commissariat of Ammunition to put these shells into production according to GAU blueprints and requirements.

The HEAT shell will allow the 76 mm mod. 1927 regimental cannon to combat enemy medium tanks at a range of up to 1000 meters.

Deputy People's Commissar of Defense, Colonel-Generalof Artillery, Voronov
GAU Chief, Colonel-General of Artillery, Yakovlev
GAU Commissar, Divisional Commissar Novikov"

RGASPI 644-2-64


  1. I suggest to no use the word "cemented armour" in this case. The armour may be high hardness homogenious or, more likely, face hardened (actually, more precise: HARVEYIZED) but not cementated. Cementation does not lead to favourable results for plates thinner than 100mm and no manufacturer made cementated plates that thin in the original decrementally hardened Krupp process entailing cementation.

    Homogenious plates have the same hardness (migh, medium or low) thorough all it´s section

    Face hardened armour can be either of those three:

    A) Harveyized armour.
    Homogenious armour plate heated up on one surface and quenched rapidly, creating a high hardness on the plate´s surface with a rapid drop in hardness if You go away from the surface. After 5-15% of the section, the hardness reach the homogenious level of the basic steel used for the plate.
    Used extensively during ww2 for tank armour. It´s better than homogenious armour in normal impact, and against inferior projectiles.

    B) Non-cementated, decrementally hardened hardened armour
    Not Used for tank armour at all. Some Navies used non cementated, face hardened armour. The plate is heated for a longer period with coal dust or illuminating gas so that the surface absorbs more carbon, lending to higher hardness deeper in the plate. It is then quenched, reheated (also known as tempering, to relieve stress) and quenched rapidly. The hardness stays high from the surface and very slowly drops to the basic hardness level of the steel mix, reaching that typically halfway through the section.
    Notice, that the british call the different homogenious armour sometimes "non-cementated".

    C) Cementated, decrementally hardened armour
    Virtually same as B) above but with an additional, thin but super hard cementated surface layer to break up projectiles (650 to 730 BHN). The thickness of the chilled part of the face varies from manufacturer to manufacturer and also with the time period considered but typically ranges between 25% and 65%. Used extensively in naval armour for plates larger than 100mm and for some armour intended for super heavy late war tank projects, such as MAUS. Drastically superior to homogenious armour (by 1/3) if attacked at normal or medium obliquity, the advantage is more pronounced with small projectiles than with large ones. Note that "small" means 203mm(!).

    1. The original document specifically said cemented, although I also suspect that the author meant surface hardened.

  2. I guess so. Do You happen to know the date of the document?

  3. Thank You. That would point to Patr.Gr. 38/HL then.