T34 Vulnerability

[jasoncawley@ameritech.net]

You are right, for the T-34 it is ~60mm at 1 km, which will go through the turret front of any model, the hull front of the F2 and early Gs, but not the later Gs, Hs, or Js. A useful correction.

Still fits the tactical picture I had, but rougher. Over the course of 1943, the Pz IVs are armored enough in the hull that the T-34/76s need turret hits at range, which probably means they want to close. That is about the same time as the Panthers appear, of course. Still fits the discontinued HEAT, but adds an extra cause for changing Russian tactical doctrine, certainly.

[Jeff Duquette]

Something that I have been curious about regarding the relatively high BHN of Soviet Armour on the T34. I typically equate very hard steel with very low ductility steel. From reading through the various postings here I am assuming that the high BHN value of Soviet armour on the T34 was not a face harding approach (ala Jerry Panzers), but reflected homogeneous plate hardness. I would therefore expect even non-penetrating hits on the T34 to result in interior face high velocity spalling. Very hard steel has very little plastic deformation prior to rupture…hard steel moves straight from its elastic stress range right into rupture…very little plastic deformation with additional applied stress.

Panzer Plate on the other hand has a somewhat softer steel on the interior side the armour. Impact energy (without armour perforation) tends to result in plastic deformation on the interior side of the plate…little or no spalling ideally.

I would therefore expect a high percentage of non-penetrating hits on T34’s resulting in crew casualties relative to non-penetrating hits on Panzers.

[jasoncawley@ameritech.net]

On T-34 armoring, I see 45mm hull and turret front on 1940 models, and 47mm hull front, 60mm turret front on the 1942 model. If you want to call that no uparmoring, that is fine by me. If you think it is simply wrong, I'm all ears.

[rexford]

The 47mm figure appears to be a single calculation that somehow was accepted as an increase that became the norm.

A 2mm increase is not uparmoring.

T34/85 armor on the hull was the same as the T34, no 60mm plate used.

T34 and T34/85 armor is hard all the way through, not face-hardened. Hits that fail to penetrate could throw off pieces from the inside.

One thing we have noticed is that early war German ammo may have been soft and vulnerable to shatter. German APCBC was used to minimize shatter.

German PzGr for 50 and 88 has about the same penetration as PzGr 39 athough PzGr 39 is capped, which implies softer rounds.

We suspect, but cannot prove, that some of the rounds available for the 75L43 during 1942 may have been APCBC but softer than ammo used during 1944-1945, thereby decreasing the penetration range. This would explain why some German units said StuG III is all they need to kill T34's at all useful ranges, and other units cry for help because T34 armor is just too angled.

Russian Battlefront site has info on 45mm ammo, which was overheated in factories and didn't penetrate anywhere what it should have. During 1941 and early 1942 45mm ammo was poor quality. Couldn't something like this have happened with 75L43 APCPC in rush to get the badly needed gun to front.

German ammo quality control, as described in British BIOS report, allowed ammo to get out with cracks. Germans reported that hits that should have penetrated often didn't.

There are many ways to approach shorter than theoretical penetration ranges, including bad ammo, bad shooting (misses are blamed on angled armor) and some variations in T34 armor. One factory in the Urals or where ever could have tempered the T34 armor to 350 Brinell Hardness, which would improve resistance by increasing ductility.

One problem with calculated penetration ranges is that the estimates do not consider high hardness armor. T34/85 vs PzKpfw IVH compares tanks with different armor types. As noted in my previous posts, Pzkpfw IVH 80mm plates had an advantage over Russian ammo that German calculations would not consider, along with 45mm disadvantage in terms of high hardness brittleness against 75mm hits.

[rexford]

Here is the problem with calculated penetration ranges summarized for Eastern Front:

1. very hard armor on T34 and T34/85 decreases resistance against 75mm/88mm hits

2. face-hardened German armor increases resistance against Russian ammo without armor piercing caps (all types)

3. Russian penetration figures are not against face-hardened armor so cannot be directly compared to German armor

4. Many Russian penetration figures are calculated from an equation that has proved to be questionable ("zementen platten", or cemented plate, is how Germans describe the equation Russians used for penetration of many rounds). When data for 76.2 penetration is 69mm at 500m and about 61mm at 1000m, be suspicious. Or 85mm penetration equals 111mm at 500m.

5. The Russian Battlefield site has good penetration data for 76.2mm, but may be confusing due to different penetration probabilities. But no face-hardened penetration data, so no good for comparing to Pzkpfw III and IV armor resistance.

So any calculated penetration ranges that do not consider hard armor, or absence of face-hardened penetration data for Russians, are bound to be of less than face value.

[Paul Lakowski]

Jason you have a funny way of admitting that your wrong...or did he even do that!

Arguing that the engineering or archival based models of penetration can't be right , just because they don't fit with your view of the world is silly and it makes you look silly too.

[PzKpfw 1]

Soviet armor with its high BHN was very brittle, Ie impacts on the glacis of the T-34 often, knocked off the drivers hatch, so the T-34 was suddenly in combat with a gapeing hole in its glacis. Other examples can be found in the US Watertown Arsenal report on the T-34 or the British report.

Also due to the effects of the BHN the T -34's armor was very vulnerable to the overmatching German 7.5cm lang ammunition, basicly the 7.5cm lang guns ammunition curt through the T-34 armor like a hot knife thru butter.

Soviet armor offered no further protection after the plate was penetrated, wheras US/UK plate of an lower BHN offered protection vs repeated impacts, even on the same area around the penetration. The first Soviet tank to adress this vulnerability was the IS-2.

Regards, John Waters

------------------

"We've got the finest tanks in the world. We just love to see the

German Royal Tiger come up on the field".

Lt.Gen. George S. Patton, Jr. February 1945.

[Jeff Duquette]

Rex Said: Here is the problem with calculated penetration ranges summarized for Eastern Front:

I knew you were gonna “clear your throat” as soon as you saw the penetration figures were based on German Clac’s and not test firing Sorry…best I can do at the moment.

[Paul Lakowski]

Originally posted by PzKpfw 1:

Soviet armor with its high BHN was very brittle, Ie impacts on the glacis of the T-34 often, knocked off the drivers hatch, so the T-34 was suddenly in combat with a gapeing hole in its glacis. Other examples can be found in the US Watertown Arsenal report on the T-34 or the British report.

Also due to the effects of the BHN the T -34's armor was very vulnerable to the overmatching German 7.5cm lang ammunition, basicly the 7.5cm lang guns ammunition curt through the T-34 armor like a hot knife thru butter.

Soviet armor offered no further protection after the plate was penetrated, wheras US/UK plate of an lower BHN offered protection vs repeated impacts, even on the same area around the penetration.

I knew some one was missing from this discussion, go to see you back John!

I was reading a research paper by Gerhing and Christmann and they showed pre and post impact hardness and showed that in the immediate area of impact hardness went up by 40 BHN points due to 'work hardning'. But only a few cms away this increase was reduced to 10-15 BHN. In truth this will make a difference , but not that much.

The first Soviet tank to adress this vulnerability was the IS-2.

John can you elaborate on what you mean by this?

Jeff said:

hard steel moves straight from its elastic stress range right into rupture…very little plastic deformation with additional applied stress.

This is true and is also similar to Adabatic shear failure.

[rexford]

IS-2 and IS-2m also carried high hardness armor, what saved these tanks was the thickness, which overmatched 75 and 88mm hits and resulted in about the same resistance as good 250 Brinell Hardness armor.

Jeff,

The real vaue of penetration reports like the one calculated by the Germans is that they show us that:

1. No one bothered to ask the tankers what they were experiencing

2. No one appreciated during WW II appreciated the key issues like we do, although we have had a much longer and more peaceful time to study and we have the benefit of all these unclassified reports from different countries.

America did the same thing, telling people 3" and 76mm gun could hole the Tiger front at 1000 yards. Try 50 yards, after shatter gap does its' thing!

[Jeff Duquette]

Regarding Real WorldTM tank crewmen experiences of MkIVF vs. T34/76, the following is from Jentz: “Panzertruppen” Vol. 2, Pg 41. This seemingly verifies that the previously quoted German “Calculated” penetration values for the 75mmL43 aren’t really analogous to US “Calculations” regarding the 3” vs. Tiger I Besides…weren’t US assumptions based upon the encouraging British Army tests of the 6-pdr vs. several captured Tigers in N. Africa?

One question I have, which is of equal importance to this thread; How certain are we that all Soviet T34 armor was BHN 390+. Is this hardness based purely upon USA testing of one T34? I came across an article several months ago implying that many of the early T34's (1940 version persumably) were constructed of imported steel plate from the United States. I think it had something to do with plate steel shortages in the USSR in the late 30’s (I will dig through my papers to see if I can find this article again...if any one is interested). Perhaps the implication is that there is a wide range in armor hardness for the T34...dependent upon plate suppliers/mill.

Anyway, here is Jentz.

<BLOCKQUOTE>quote:</font><HR>Farther to the north, the Panzertruppen under Heeresgruppe Mitte had also succeeded In stabilizing the situation in March 1943. The Panzers' ability to knock out enemy tanks during these battles is related in the following detailed report compiled by the 5-Panzer-Division for the period from 22 February to 20 March 1943. This shows the relative effectiveness of each type of Panzer as well as the ranges at which the Panzers were firing:

Number and Type of Enemy Tanks Knocked Out and Effect of Types of Ammunition Used

<UL TYPE=SQUARE> 7.5 cm Kw.K. L/43 in 4 Pz.Kpfw.lV17 KW-1, 26 T34, 1 T26, 1 Mark II, 3 Mark III,1 General Lee

Pzgr.39 was fired at ranges from 1200 to 1600 meters. Every hit caused a destructive effect with the tank going up in flames. Two to three Pzgr.39 rounds were expended per tank killed. Gr.38 HLB ammunition was seldom used. One to five rounds were required to set an enemy tank on fire.

7.5 cm Kw.K. L24 in 9 Pz.Kpfw.III and 5 Pz.KpfwIV

1 KW-I, 6 T34, 1 T60, 4 T26, 1 Mark II, 4 Mark III, 2 General Lee

Gr.38 HLB had a destructive effect when fired at ranges under 600 meters at the hull and rear of the KW-I. The T34 was also engaged by firing at the hull. Three to six rounds of Gr.38 HLB were required to kill each enemy tank.

5 cm Kw.K. L/60 in 10 Pz.Kpfw.III

2 KW-1, 18 T34, 3 T70, 7 T60, 4 T26,

2 Mark II, 6 Mark III, 2 General Lee, 3 types not reported

Only the hull and rear of the KW-1 and T34 were engaged at ranges under 150 meters. Very seldom does the tank catch on fire. Two to five rounds of Pzgr.39 or Pzgr.40 were expended to kill each KW-1 or T34. One to three rounds were expended to kill each lighter tank.

5 cm Kw.K. L/42 in 17 Pz.Kpfw.III

5 T34, 2 T60, 4 Mark II, 3 Mark III,

3 General Lee, 3 type not reported Same ammunition use and effect as 5 cm Kw.K. L/60.

<HR></BLOCKQUOTE>

[Jeff Duquette]

self serving bump...still curious about T34/76 plate hardness.

[PJungnitsch]

Not wanting to belabour a point, but this looks more like soft armour than hard, doesn't it?

A chemical analysis of the armor showed that on both tanks the armor plating has a shallow surface tempering, whereas the main mass of the armored plating is made of soft steel.

http://history.vif2.ru/library/archives/stat/stat7.html

Perhaps there is no standard for T-34 armour, that variations in quality control could result in all kinds of hardnesses, depending on the factory, the foreman, who was on that shift, etc.

[ 04-10-2001: Message edited by: machineman ]

[Jeff Duquette]

Thanks for the link machineman…it’s been awhile since I read that report. My memory is obviously going as the report clearly indicates the armor plate on the test T34 was constructed of soft steel:

<BLOCKQUOTE>quote:</font><HR>A chemical analysis of the armor showed that on both tanks the armor plating has a shallow surface tempering, whereas the main mass of the armored plating is made of soft steel.

In this regard the Americans consider that by changing the technology used to temper the armored plating, it would be possible to significantly reduce its thickness while preserving its protective ability. As a result the weight of the tank could be decreased by 8-10%, with all the resulting benefits (an increase in speed, reduction in ground pressure, etc.)<HR></BLOCKQUOTE>

Unfortunate that some specific BHN values are not indicated (or did I miss that somewhere).

As far as belaboring the point…I don’t think you are. Weather a certain portion of T34’s were constructed of softer armor than BHN = 395+ was where I was trying to go with my above post\question. One other tid-bit is that S. Zaloga implies that the armor plate on early T34’s (model 1940) was more in alignment with British and American hardness specifications.

[rexford]

The Americans, Germans and British tested T34 armor during the war and it was all hard homogeneous. No face-hardened.

When the Germans duplicated T34 armor during early 1942 to shoot at, using the same chemical composition as T34, they had Brinell Hardness over 400. No 250 Brinell, no 350 Brinell. All over 400 Brinell.

Americans tested several T34 and all over 400 Brinell.

Say America sent Russia 45mm plates with typical range of flaws. 45mm at 60 degrees with medium flaws resists 75mm hits like 102mm at 0 degree resistance. This would give 75L43 a 50% penetration chance at 1200m on head-on hits. But we don't know how many, if any, T34 were made with U.S. "softer" plate.

Regarding Aberdeen finding shallow surface tempering backed by soft armor, we have also read that T34 turret armor was soft copper or brass sandwiched between two thin steel plates. Nonsense.

There are many possibilities here:

1. misinterpretation of engineer findings

2. Stalin sent over an "April Fool" specimen, "soft steel" generally means steel that has not been hardened enough to qualify as armor plate

3. Americans accidentally sent Russia face-hardened armor for T34, so Stalin sent it back on T34 ot see if Americans noticed

Bulk of evidence suggests that "most" or "practically all, if not all" T34 used high hardness homogeneous armor.

[rexford]

So, every hit on T34 and other enemy tanks at 1200 to 1600 meters range destroys target.

75L43 sounds pretty effective to me, no mention of endless bouncers till a round strikes the turret. Since the hull front is most of the frontal target aspect, the statement suggests front hull was no problem from 1200 to 1600 meters at the angles met in combat.

And note that the report doesn't say except for hits on driver hatch, which always bounced. So we can read in alot more and make it sound like driver hatch is 45mm thick, too.

Well, thanks to the quotation provided by Jeff, T34 armor seems mighty vulnerable to 75L43 at extreme ranges, which must include frontal hits on the hull.

But was there alot of variability in T34 armor? Many posts seem to suggest that there was some "more resistant" armor.

[Skipper]

> But was there alot of variability in T34 armor?

Keeping in mind that we are talking about wartime production on many different metallurgy plants, some of them not even originally designed to manufacture armor plate at all, there should be.

[Olle Petersson]

<BLOCKQUOTE>quote:</font><HR>Originally posted by rexford:

Since the hull front is most of the frontal target aspect, ...<HR></BLOCKQUOTE>... unless the target is hull down, as was common practice.

I've seen a couple of notions that 2/3 of all combat hits were on the turret.

(Another figure is that 90% of all hits are >1m above ground level.)

So when designing AFVs the primary place for armour is the turret front. Then glacis and turret sides.

Cheers

Olle

[Jeff Duquette]

Rex:

This is the passage from S. Zaloga (Osprey, T34/76, Medium Tank 1941-1945, Pg 36) I was referring to in my last email to you. The second sentence regarding the early 1940 Model T34 is what caught my eye. This my simply be a problem of my interpretation of what Zaloga is saying. I took the second sentence to imply that BHN of the earlier 1940 version of the T34 to be on par with British and American plate. Vague on my part at best…but after seeing the report machineman provided a link to, I started to wonder.

<BLOCKQUOTE>quote:</font><HR>The hull of the basic T-34 Model 1942 was constructed using homogenous rolled steel armour plate of a rougher finish than comparable British or American armour but of greater strength, with the 45mm glacis plate having a Brinell hardness of 354 to 400. The early T-34 Model 1940 tanks were built to a standard which was on a par with western European or American designs. By the middle of the war, the workmanship had declined, though the plant inspectors were careful not to permit this to affect the combat performance of the tank. The welding was mediocre, though not so poor as to result in weld failures. The cast turret was not to Western standards, with some porosity evident on the turret surface. However, this did not necessarily reduce the effectiveness of the armour, and British tests found that the turret casting had a high degree of hardness, on the order of 370-375 Brinell.<HR></BLOCKQUOTE>

[rexford]

The T34 in the Russian Battlefield article is the T34 that the U.S. analyzed, and the steel was over 400 Brinell Hardness and homogeneous. The photo's associated with the T34 America received and analyzed and the T34 in the Russian Battlefield report are ONE AND THE SAME.

There was no T34 armor with shallow tempering on the surface and soft armor underneath, BECAUSE tempering does NOT harden steel, it softens it and increases ductility.

Look at the front of a T34 Model 1941 or Model 1942, most of the hittable area is on the hull (most of the seeable turret front is highly angled and ricochets would result).

During early 1943, the Russians were on the offensive and the Germans were trying to STABILIZE the front (as noted in the 5th Panzer report), thus allowing FOUR PzKpfw IV with 75L43 to pick off over 20 T34 and almost as many KV-I. If 26 T34 were hulldown, would FOUR PzKpfw IV have attacked them and been able to pick off so many before being destroyed themselves????

From the statistics presented in the 5 Panzer report, it is OBVIOUS that the Russians were attacking. PzKpfw III with 50L42 are able to get within 150m for kills when Germans are attacking HULLDOWN T34?????

[rexford]

T34 built to American and British standards does not automatically mean the same Brinell Hardness, it seems to mean the same workmanship and consistent quality of welds, finish, surface cleanliness, whatever.

British Brinell Hardness readings are LOW, because they used a portable Poldi machine.

WW II high hardness armor is brittle against 75mm hits, regardless of the quality. And it only gets worse, it doesn't get better. Were some T34 tempered to a point where the armor was 350 Brinell Hardness? Possible.

But when the Germans decided to test T34 type armor in firing tests, they didn't have some plates at 350 Brinell, some at 400, some at 450. They were all over 400 Brinell.

Based on our analysis of American and German tests during WW II against high hardness armor:

350 Brinell is 6% more resistant than 400 BHN

450 Brinell is 5% less resistant than 400 BHN

If 75L43 penetrates 400 Brinell T34 glacis at 1500m, it penetrates 350 Brinell glacis at 1250m, and 400 Brinell glacis at 1750m.

That's how hardness variability influences 75L43 penetration ranges, and if the quality of the armor is subpar, the ranges increase all around.

[rexford]

When was 75mm HEAT for StuG III available? Michael Wittmann earned his early "bones" knocking out T34 and KV tanks in a StuG IIIB, and we wonder if he used APC or HEAT.

[Paul Lakowski]

<BLOCKQUOTE>quote:</font><HR>Originally posted by rexford:

When was 75mm HEAT for StuG III available? Michael Wittmann earned his early "bones" knocking out T34 and KV tanks in a StuG IIIB, and we wonder if he used APC or HEAT.<HR></BLOCKQUOTE>

Early 1942 ...was aready in use by april 1942 [ mentioned in StuG battle reports]

[Jeff Duquette]

David Honner in Guns and Armour indicates: "The Gr.38 HL entered service in

June 1940. The service dates of later patterns of German HEAT projectiles

are unknown." However, Jentz in; Tank Tactics of North Africa indicates

that a STUG III captured in N. Africa in 1942 had 20 rounds of Gr.38 HL/A

(an improved HEAT round from the Gr.38 HL).

[Jeff Duquette]

The following quote is from Wolfgang Fleischer's "German Light & Heavy Infantry Artillery, 1914 - 1945". This may be a bit of a stretch but I am assuming that the July 1 1940 reference by Fleischer may be the same or similar round as the Gr. 38 HL/A employed in the STUG III's 75mmL24. The thing that throws this off a bit is that David Honner indicates Gr. 38 HL/A penetration capability is 70mm and Gr. 38 HL/B is 75mm... the mid or late war Gr. 38 HL/C is rated at 90mm.

"In general it can be estimated that the infantry gun proved itself well, especially where it, thanks to its mobility and firepower, could advance the forward movement of the attacking infantry. Organization, formation and proper training contributed to providing the infantry with the necessary superiority at focal points. But naturally there were also disadvantages to such a weapon designed for very special uses. All infantry guns were only of limited use as antitank weapons, a task which took on decisive importance in the war and had to be carried out by all types of service arms.

On July 1, 1940, as ordered, the 7.5 cm Infantry Gun Shell 38 HL/A, an armor-piercing projectile, was introduced for the 7.5 cm infantry gun. With this shell, regardless of the range, 75 millimeters of armor plate could be pierced (later, with the HL/B version, this was raised to 90 mm). The comparable ammunition of the heavy 15 cm infantry gun even had a penetrating power of 140 to 160 mm. In spite of that, the infantry guns' chances of success in antitank action were limited. The shot range in direct fire and the field of traverse were simply too limited."