Paul Lakowski wrote:German armor quality started to decline about the same time soviet AP shot quality improved. Hetzer armor is 195BHN to 220BHN while Tiger-2 armor is around 220BHN...thats mid 1944. Jagd Panther Armor was supposed to be 285-345BHN but was tested with 260-310BHN, while the mantles ended up 230-260BHN . The panther armor was reported tobe 270 BHN , while the mantle cast hardness was reported to be 210-245 BHN.THese are low hardness.Source Jentz Panzertracks and several British firing trials. Resistance of plates was reported to vary widely at this time due to shortages of key alloying agents.Harri wrote:Christian:
Later model of JS-2 is actually rather similar to JS-3. Main differences are different turret and "reshaped" frontal hull.
Paul:
I have seen many kinds of figures so which one to rely on? I agree German main ammo was armour (and HEAT) shell. APCRs were reserved for smaller calibre guns (and later actually for "emergencies" only).
Only Soviet 100 mm L/54 gun could penetrate 155 mm (90/0 degrees, 500 m) and nothing more. Other guns were inferior to that. Do you have post war figures? JS-3 was used until 1970's and I'm sure their ammo was also improved a lot after the war.
Soviet 122 mm tank gun D-25M-1943 (used in JS-2 and 3) was based on A-19 gun (without muzzle break but barrel length L/45) but this new modification had L/43 barrel. Soviets didn't develop completely new guns during the war so the improvements in penetration could only be achieved in increasing the muzzle velocity significantly (in practise length of gun) or developing a new different type better piercing shell. The earlier mentioned gun was only slightly better.
Soviet armour shell weighted 25 kg and its muzzle velocity was 790 m/s. In smaller calibres Soviet subcalibre shot was only slighly better than their normal armour shell but I don't know if it was used or even developed during the war for 122 mm gun?
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It is likely that also German armour steel became worse in quality during the last months of war but in 1944 the difference in quality was significant in favour of Germans. Not even Soviets couldn't produce equal steel without additional metals used for hardening the steel.
THe Russian tested their penetrators on RAS [Russian Armored Steel] thats has nominal hardness ~ 440BHN while their penetration criteria is 80% certified penetration...compared to german tests that were 50% ballistic limit tests on Plates around 300 BHN. THe difference in penetration is ~ 28-30% so that 155mm penetration at 500m range for the BR412 is infact ~ 200mm Vs german plate.
Russian armor piercing projectiles improved from late 1943 on because the general steel employed went up from 460 BHn steel to 550 BHN. German AP shot was generally around 600-620 BHN but started to decline to 580-590 due to the larger shots. Each 10 BHN points makes >1% difference in penetration...so early soviet penetrators were 20% below the norm...by late war this was improved to 90% due to improved steel quality. [Source: ARTCOM article AFVNEWS May-2003- Miles Krogfus],
The above mentioned source also reports that T-34 armor was 430-440BHN while turret casting was 444BHN. IS-II hardness was ~ 450 BHN cast turret and 440 BHN hull plates.While another doc puts the T-34/85 hardness @ 350-400BHN
Actually I think you or your source have it backwards. Hardness increases britleness which usually leads to easier breaking of armour. WWII gunnary and ballistics by lorin bird et al. Low hardness allows the armour to absorb most of the shells enegry resulting in little or no penetration. The ger often times covered thier soft armour with special face harded armour that caued dam to the AP nose decreasing max pen even more.
Also to compore the two different numbers bettween rus and ger test you just add together the 80% and 20% and divide by 2. That should compare directly the rus and ger pen numbers.
One of the major problems for the IS2 122 mm tank was its small space too large gun and heavy two piece shot. It meant its gun had a VERY low ROF maybe 3-5 times worse than the ger 88s.