Armor quality of the Tiger I

[critical mass]

Unter-officer Bohm writes this in his after-action report from 19 Edit:July 1943:

"...one of the Ferdinand's from my unit took a hit to the side armour from 400m (it got surrounded by 7 T-34 tanks). The shell holed the armour but didnt produce any additional damage inside."

Source: Munch K. The Combat History of German Heavy Anti-Tank Unit 653" p. 53-54.

It looks like this was a subcaliber shell, small mass of the core and lack of HE filler could possible produce such results after penetration. M. Svirin reports in his book "Tankovaya Mosch. Part 3. Domestic Tank Design between 1943-1955." that the 76mm subcaliber shells were designed by autumn 1942 and after a small pre-production batch at the end of that year entered mass production in the spring of following year.

Excerpt from the report on ballistic trials carried out on the order of commander of 13th army N.P. Puhov on one of the disabled "Ferdinand"s from 20-21 Edit:July 1943:

45mm ATG Mod:1937 fired 6 subcaliber shells at 300m at side armour at 90° angle, obtained 2/6 perforations. 3 shots from 150m, 3/3 perforations. Normal AP shells fired at the frontal armour only made dents 25-30mm deep.

76mm ZiS-3 ATG fired 3 shots from 400m at the side armour, 3 holes 27mm wide. AP shell made dents 22-30mm deep and 100mm wide. Firing the subcaliber shell at the frontal armour at 200m left dent 100mm deep 110mm wide, core is left stuck in the plate. AP shell left a dent 37mm deep 110mm wide.

76mm APBC-HE cannot be excluded. This shell would have a chance to hole the plate under fortunate conditions (perpendicular impact) but not explode inside due to filler/fuze action and shell break up. It´s what You would expect from a broken up shell undergoing low order detonation before passing through the plate. Similarely, APBC-shot is possible if the hole caused from impact was smaller than the diameter of the shell (but considering nose shape et al. somewhat less likely).

On the basis of this logic, I will say that an 82mm plate, like the ones used in the side armour of Tiger I tanks, should not be rated as "bad quality" because of their brittle tendency under attack at zero obliquity by 75 and 85mm AP shells, but rather by how they behave under attack from 57mm, and similar, allied guns, where it demonstrated good performance.

The mode of failure of armor plate also depends on the geometry of the attacking projectile. A high quality pointed projectile (say 17 pdr APCBC, 75mm Pzgr39, ....) will not expose brittleness becuse the attack is one directed against the limit of the plate to resist plastic deformaion. On the other hand, a blunted nose shell cannot be easily resisted by plastic deformation. Soviet 76mm-122mm wartime ammunition was low quality shot, pointed or blunt and this almost always will induce plugging / discing failures. Its not an attack on the limit of resistence of the plate to deform plastically but an attack on the shear resistence of the armor plate.

[Peasant]

76mm APBC-HE cannot be excluded. This shell would have a chance to hole the plate under fortunate conditions (perpendicular impact) but not explode inside due to filler/fuze action and shell break up. It´s what You would expect from a broken up shell undergoing low order detonation before passing through the plate. Similarely, APBC-shot is possible if the hole caused from impact was smaller than the diameter of the shell (but considering nose shape et al. somewhat less likely).

Earlier I was wondering whether the unusually poor performance of the soviet 76mm AP shell in May '43 trials against Tiger was due to projectile shatter, as the T-34 gun should've, at least, produced some bulging on the back of the plate when fired from less than 400m distance. As we know the hardness of 82mm plates on the Tiger I captured by the british in 1944 was only about 260-265BHN rather than 300BHN it was a year earlier. This would've influenced the the extent of damage inflicted to the attacking shot and could explain the discrepancy between the results of 1943 and 1944.

On the basis of this logic, I will say that an 82mm plate, like the ones used in the side armour of Tiger I tanks, should not be rated as "bad quality" because of their brittle tendency under attack at zero obliquity by 75 and 85mm AP shells, but rather by how they behave under attack from 57mm, and similar, allied guns, where it demonstrated good performance.

The mode of failure of armor plate also depends on the geometry of the attacking projectile. A high quality pointed projectile (say 17 pdr APCBC, 75mm Pzgr39, ....) will not expose brittleness becuse the attack is one directed against the limit of the plate to resist plastic deformaion. On the other hand, a blunted nose shell cannot be easily resisted by plastic deformation. Soviet 76mm-122mm wartime ammunition was low quality shot, pointed or blunt and this almost always will induce plugging / discing failures. Its not an attack on the limit of resistence of the plate to deform plastically but an attack on the shear resistence of the armor plate.

Yeah. In this case brittleness would be judged on the basis of cracking of the area outside the hole and the amount of additional backspall ejected besides the main plug.

[critical mass]

The best way to judge the extent of brittleness is to have controll over the ambient conditions (temperature in particular) and make microscopic analysis of the fracture (not often done in these tests). If the backspall/ disc exhibits grain fracture, the plate responded brittle. If it shows fibre or predominantly fibrous fracture with only little grain present, the plate responded ductile. The scale is not ordinal scale level (either ductile or brittle) but a metric scale level with reference to temperature. There is always a ductile-brittle transition temperature, which can vary for ww2 period steel armors from approx. -50°C to +50°C. Of course, the lower the transition temperature, the more ductile the plate will perform.
Different failure modes of the plate (plastic deformation, shear failure or shatter) do correlate (but not equate!) these results, too. It´s a somewhat complicated topic when projectiles and armors are compared cross country.

In regard to the May 1943 trials, the difference can be as simple as firing live or inert shells. I haven´t checked this, but its certainly worth to keep in mind. An HE-filled shell would undergo low order detonation if the projectile body is broken up by impact (in average only 1/3 as powerful as a high order burst) and this will contribute to a reduced ability of the shell to punch out a hole (fragmentation of the shell takes plate outside the armor, reducing instantly the mass of the projectile parts still in contact with the armor plate). However, trials with inert shells do not experience this "cap in holing performance", part of the reason why the british got rid of their HE-filler in the latter part of the war entirely (the SU, too issued -SP projectiles with removed HE-filler).

[Peasant]

The question about armor quality of german vehicles is closely related to another one, the quality of soviet ammunition. We all know that usually soviet shells defeat a given target at lower ranges/higher striking velocities than their equivalent western counterparts, but I thought after that point they are just as effective and consistent.

After carefully ordering all the hits by soviet 85mm blunt headed shells it became obvious that about half of them failed to defeat a relatively mild target of vertical 80mm of Tiger II lower side hull plate at ranges up to 1500m, while the official penetration figures(calculated through DeMarre formula) indicate that it should have no problems defeating this target at striking velocities down to 600m/s, equivalent to the distance of 2200m.

Now that I think about it, there can be a different explanation. In the 1943 trials against Tiger I all hits with 85mm blunt headed shell penetrated the side armor with ease at 1500m distance. It's hard to believe that shell quality suddenly dropped in 1944 so much that not one but several shells failed to do any damage to the same target (80mm/0°) flat side armour on Tiger II here.

What I think is most likely is that soviets messed up the external ballistics (again) and used the FT for BR-365K, the sharp tipped shell, for converting striking velocities to distances for both types of shells. If this were the case, then hits with blunt headed shells at "nominal" 1500m range in actuality did not have the striking velocity of 652m/s but only 562m/s(corresponding to 2700m range) which is more in line with what we know 80mm of vertical RHA can stop.

Alright I've got the answer to this mystery. This cant be an issue with external ballistics as the original document explicitly states that these shots were made from real distances. I have found another schematic of Tiger II, this time with roadwheels on and overlayed the soviet shot diagram on top.
All shots with 85mm gun that didnt penetrate flat side armour passed through the roadwheels that were left mounted on the hull although this cant be seen in the original schematic nor is mentioned anywhere by the writers of this report that this could've affected the results.

It seems that effective thickness of the lower hull protected by roadwheels is at least 90-100mm effective. Good to know for future reference.

[critical mass]

Well done Peasant.

[Yoozername]

Some recovered German Pzgr

75cmpantpensherm.jpg

[Yoozername]

some video

utubepant.jpg

2:23 time
https://www.youtube.com/watch?v=aRC8LT2gBUA

[Peasant]

April '43 soviet test. The penetration of the Tiger I side armour by 57mm UK gun at 1000m was an unfair hit. It was too close to a hole from a previous penetration. The other 2 hits at 1000m failed to penetrate, but it looks like they've hit at a small 15-20° angle on the rounded turret, so it's unclear whether or not they would've penetrated with a perfect 0° hit.

Edit: For that matter, the penetration at 1000m by the soviet 57mm gun can be considered unfair as well, as it is close enough to the unsupported edge of the plate to cause it's plastic deformation.

[Peasant]

Finally, more details about this trial. I've seen only tiny snippets of this report before today:



Source: https://forum.il2sturmovik.com/topic/75 ... nt=1145041

[Peasant]

Not very detailed, but better than nothing. Of note is no cracking of Tiger's driver's plate from penetration of 100mm AP projectiles.

[Peasant]

I'm sure most people reading this have not seen this before:



(upscaled and cleaned the image, still barely readable)
Source: https://www.kbismarck.org/forum/viewtop ... 9f4#p43065

[Peasant]

76mm gun. [likely the ZiS-3 ATG]

Distance: 500m.
Shell: AP
Target: Side.
Results: 3 hits. No perforations. Depth of penetrations: 60mm.

Distance: 200m,
Shell: AP
Target: Side.
Results: 10 hits on sloped side plate. No perforations. Depth of penetrations: 60mm.

Distance: 300m,
Shell: Subcaliber
Target: Side.
Results: 2 holes in the vertical side plate and 2 penetrations through suspension. [unclear whether the last 2 shots perforated the main armour or not]

Distance: 400m,
Shell: Subcaliber
Target: Side.
Results: 2 penetrations of the sloped side plate.

Distance: 600m,
Shell: Subcaliber
Target: Side.
Results: 3 shots bounced off the turret side.

Distance: 200m,
Shell: Subcaliber
Target: Side.
Results: 3 perforations of the vertical side plate.

Distance: 400m,
Shell: Frag
Target: Suspension.
Results: Destroyed one roadwheel.

...
(There were more shooting done with other soviet guns, but the results are nothing unexpected. I can translate if you want.)
...

Interesting parts:

Depth of penetrations: 60mm.

In the 1943 trials on Tiger I this gun (well technically the F-34 gun on a T-34 tank) achieved:

Distance: 400m,
Shell: AP
Target: Side.
Results: Dent 35mm deep.

Distance: 200m,
Shell: AP
Target: Side.
Results: Dent 40mm deep.

and this is against a vertical plate, while here it achieved deeper penetrations against a plate of same thickness sloped at 25° (provided the measurements were taken in the same frame of reference). Could mean this gun was using BR-350B shells with better integrity than the early models.

[Denniss]

image shows a Tiger II ?

[Peasant]

image shows a Tiger II ?

Yeah, just this thread has evolved from talking only about Tiger I into thread about german armour quality in general.

Edit: Found helpful info, the penetration table for 76mm soviet AA gun that was used in ballistic trials of first Tiger in 1943. From it I've reverse-DeMarre'd striking velocities at various distances and interpolated the data points:

[Contender]

...
(There were more shooting done with other soviet guns, but the results are nothing unexpected. I can translate if you want.)
...

Yes please.