George Forty on Panzers vs T34, March 1943

[rexford]

Pages 126 and 127 from Forty's GERMAN TANKS OF WORLD WAR TWO present an account of two Tigers taking on a pack of T34. which is taken from German Defense Tactics Against Russian Breakthroughs (U.S. Department of the Army pamphlet No. 20-233).

The T34's used to stand outside villages in ambush, at 1350 yards range (1235m), and wait for the panzers to come out to play. At 1235m, the T34 were safe from the panzer guns ("hitherto safe distance") according to the write-up since the panzer guns were outranged. Kharkov area, Grossdeutschland Division.

I've thought about the situation many times and the main opposition likely to be facing the Russians would be PzKpfw III with 50mm L60 guns or PzKpfw IV with 75mm L43. If 1235m is a safe range it suggests that the turret front is immune.

At 1235m, the 50mm L60 gun firing APC would penetrate about 56mm vertical plate at about 300 Brinell Hardness, while the 75mm L43 APCBC would defeat around 101mm vertical.

German firing tests with 50mm rounds against 40mm-55mm of high hardness T34 type armor suggest that the resistance might be boosted by 20% or so above 300 Brinell plate. This potential boost from high hardness armor could help explain why 50mm L60 hits at 1235m would bounce off the front of a T34 at 1235m.

The thing that puzzles me is why the Grossdeutschland Division would not have quite a few PzKpfw IV with 75mm L43 during March 1943, and T34 would have grown quite accustomed to fighting PzKpfw III's in the area with all the limitations of their APC rounds.

If the T34 were standing at 1235m due to ineffectiveness of the 75mm L43 gun on PzKpfw IV, this may have some significant meaning in terms of how effective the 45mm front hull plates were against 75mm APCBC (although we would still have to explain the turret front and mantlet safety against 75mm L43 hits).

Lorrin

[JasonC]

Gee, are you actually starting to notice? (grin)

CMBB StuGs are modeled like Tigers. They are invulnerable to Russian 76s even with improved ammo down to point blank range. Their own gun kills T-34s through any plate at 1500m. It takes all kinds of tweaked armor grog minutae to pretend this is reasonable for a mere StuG, and always did. In the real deal, Tigers mattered because they had those characteristics. For the first time.

Way back before BB was released, I was offering you AARs in which StuG drivers with 75L48 held their fire in ambush to 800m range, to be sure a round would penetrate any plate. You told me instead that Russian armor was too thick to resist well (always distinctly counterintuitive) and therefore should fall apart at 1450m, even the glacis. Now you notice other AARs consistent with the previous, and not with the latter.

My tactical read, not based on armor quality minutae but on what they were doing, is that the Germans killed T-34s through the hull at about 1000m. While T-34s, once they got improved ammo (capped, BR-350B), killed 80mm front plain German panzers and StuGs at at 500m. This meant the Germans had a serious edge but not "kill at any range, invulnerable to replies" with just the vanilla armor types.

Meanwhile, with the Pz IV, the turret is distinctly thinner, and vulnerable at longer range. The turret of the T-34 (mid war models) is weaker only for flat hits, about the middle half of its exposed area - because it is thicker armor and still gets some slope for the other half or so.

At longer range, the hull of either is well protected. (The Pz IV better, sure). The Panzer needs a flat turret hit rather than a high angle one. The T-34 needs just a turret hit. Thus, one reasonable dueling location for the T-34 against IVs (not StuGs) was beyond the range their own glacis was vulnerable.

Even more so when there are 50L60s in the mix. Those outperform their historical counterparts in CMBB, because of T-34 turret modeling. Against the glacis the 50mm is hopeless. On turret hits, it needs close range - 500m - and a flat hit. At those ranges the T-34 is dangerous back. APCR helps only on flat hits, which are rare against T-34 turrets. But might extend this to the 800m range occasionally. 50L60 Pz IIIs had to kill from the sides, because 65mm with some slope or 60 degree slope are both pretty monstrous against that round.

Into all of this the Tiger walks as the first unkillable beast that kills at any range. So it actually matters. But not in CMBB. In CMBB you can pay half as much for an uber-StuG that will do it all. The real Germans should be so lucky.

[ November 14, 2003, 02:34 PM: Message edited by: JasonC ]

[rexford]

JasonC,

Yes and no.

Why would a T34 M43 with 70mm slightly sloped turret front armor and a 52mm flat mantlet hanging out in front of the turret be safe from 75L43 APCBC hits at 1235m?

A report in Jentz has 75L43 APCBC destroying attacking T34's at 1200m from any angle and 1600m max.

Valera Potapov has seen a Russian firing test report where 75L43 APCBC consistently blew through the T34 glacis at 1000m with a 30 degree side angle.

Another report in Jentz indicates 1000m or so is about it for 75L43 vs T34.

My response to you is:

A. the data suggests extreme variability in T34 front hull resistance, which could result from some factories using a reduced plate hardness (350 Brinell Hardness plates could be less vulnerable than 450 Brinell).

B. the AAR for T34 against StuG III front could be penetrations of the front superstructure (30mm and 50mm plates at a high angle), which makes up a much bigger percentage of the frontal target aspect than the 80mm driver plate

C. there is insufficient data to define a single effective resistance for T34 front hull

D. the Russians manufactured (starting late 1943) improved BR-350B rounds, with 10% more penetration against face-hardened armor than the standard BR-350B, although in very limited numbers. The special BR-350B penetrated 83mm face-hardened at 500m, the regular round 76mm. There's the 500m penetration against 80mm face-hardened.

A round with 76mm penetration would obtain some successes against 80mm plates, though less than 50% of the hits.

E. most Russian 76.2mm AP rounds were capped, but it wasn't an armor piercing cap it was a windscreen to reduce air resistance.

F. our predictions for 75L43 APCBC against T34 front hull are consistent with the majority of combat reports and Russian firing test trials, so at this point we are in the lead.

[ November 15, 2003, 09:20 AM: Message edited by: rexford ]

[JasonC]

"Why would a T34 M43 with 70mm slightly sloped turret front armor...be safe from 75L43 APCBC hits at 1235m?"

Those plates wouldn't be, without side angle anyway. But they are tiny plates compared to the overall size of the tank. If hull hits bounce, and half the hits in the turret area encounter 70mm plus significant angle (and plenty of the turret region of a T-34 does have such angle), then few hits will "stick" and tactical AARs will report failure. Tactical reports do not turn on "ever or never"s, and rarely refer to dead on shots without any side angle (though that is somewhat more common turret to turret, due to dueling).

"A report in Jentz has 75L43 APCBC destroying attacking T34's at 1200m from any angle"

But not any plate. If there is some plate vulnerable at 1200m from the front - the middle of the turret front - then the statement is true - a T-34 can be destroyed by 75L43 through any angle. Even if they are bouncing off the glacis.

"and 1600m max"

Side hits. No problem.

"75L43 APCBC consistently blew through the T34 glacis at 1000m with a 30 degree side angle."

Additional side angle adds little to a plate that is already 60 degrees. And 1000m is what I am saying the lethal range was.

"Another report in Jentz indicates 1000m or so is about it for 75L43 vs T34."

Quite. So do the tactical practices of both sides. But CM does not show this, remotely.

"the data suggests extreme variability in T34 front hull resistance"

No it doesn't. Reading "any angle" to mean "any plate" just makes the glacis look as weak as the middle of the turret front. You need to posit taffy armor characteristics to stretch over both of those, sure. But it is just a misreading.

Any angle means some portion of the tank is vulnerable whichever way you rotate it - that it cannot adopt some partially turned facing capable of rendering it invulnerable. It does not mean every portion of the tank is vulnerable whichever way you rotate it. It would not occur to anyone that it should. (89 degree glances from the turret front, anyone?)

It was never very plausible that 25-30% harder armor resists 85% as well, against rounds that are marginal against either.

"T34 against StuG III front could be penetrations of the front superstructure (30mm and 50mm plates at a high angle)"

They don't penetrate there in CM, either. 30+50 is, if anything, somewhat tougher - unrealistically so. In fact, 20+50 Pz IIIs generally bounce everything down to 500m, which is the performance actually seen only with 80mm. StuGs face occasional partials at 100m if the side angle is absolutely zero. Otherwise they bounce everything. This is Tiger performance and unrealistic. The Russian 76 is woefully undermodeled, German 20+50, 30+50, and 80 is overmodeled.

"there is insufficient data to define a single effective resistance for T34 front hull"

If there is insufficient data for the T-34 front hull, there isn't a single bloody plate in the whole bleeding war for which there is "sufficient" data. Sufficient to tone down uber-StuGs, no that requires a decree of papal infallibility. Sufficient to turn Russian 76mm into junk, requires an allegation.

Here is my story to set against your "all penetrations are magic special rounds that nobody really had" tales for the Russian 76. Typical German armor quality in 1942 and 1943 deserves at best only 95% rating. Period. No mysteries remain.

Layered armor gives about thick plus .8 thin, or -4-5mm effectiveness for 20+50 and 30+50, in addition. Thus 65, 72, and 76 for successive generations of German armor on the plain Panzers and StuGs. (Whether Tiger side armor deserves 100 quality as an exception I consider open, but "not proven". 82@95% would account for all the tactical evidence I've seen).

"Round" should give median performance 45 degrees, only about 1/3 as low as 30. That would deal with T-34 turret undermodeling.

BR-350B is a capped round. Glantz among others states that the improved ammo available to the Russians by 1943 (not 44) had already extended the usefulness of the 76 and increased its lethal range against typical panzers by a factor of 2. Which I take to mean roughly 1000m vs. 20+50, still only 500m vs. 80mm fronts. All the RB numbers track. CMBB is the outlier.

Nobody else in history has maintained that plain StuGs were invulnerable to Russian 76mm from the front, down to point blank range. The StuG aces all say first hit, low profile, and superior optics were their main advantages. If they were invulnerable they would have noticed - Tiger crews certainly did. They weren't.

"our predictions for 75L43 APCBC against T34 front hull are consistent with the majority of combat reports"

2 out of 3? If one credible report says "we couldn't kill them at 1200m" and you have them routinely killed at 1600m, then no that is not "consistent". You might have better numbers than CMBB does, that is your affair. CMBB continues to screw the Russians and goose the Germans, and anyone who reads the AARs knows the historical Germans never had it so good.

Put a .9 armor or ammo qualities in front of everything Russian and a 1.0 to 1.05 in front of everything German and you get CMBB. Put a .95 in front of both and you get reality.

[Mr. Tittles]

Since the game does not model shot distribution as it was for each vehicle, why are you debating penetration all the time?

The truth is, the stug (without the pigs head cast armor) has a vulnerable spot on its gun shield. The stug actually has a collection of well armored/sloped spots. Stugs would have been well advised to not let AP firing weapons get within 500-600 meters.

The turret front 'over-kills' in the game are just annoying. The panzer IVs 50mm turret front weakness is rather small if you dont count the gunshield. The turret is actually pretty small to begin with. The same with T34 turrets.

[Kozak]

This is probably anecdotal, and not based on real science, but the one serious armour weakness that my uncle mentioned about his experiences commanding the T-34 was the drivers hatch in the front hull.

To get the slope on the front the driver was put in a very uncomfortable semi-reclining postion. The driver also had bad vision and ventilation so sometimes they would keep the hatch partially open on route marches. Troublesome with an AT gun or tank ambush of the column from the front.

The hatch was part of the hull front rather than the kind of "Jack in Box" top hatch of the PZIII and PZ IV driver. I don't know whether the hatch itself had less armour than the plate around it to allow it to be opened, but the perception was that it was a weak point. They also had the perception that the Germans aimed at the hatch on a front shot.

They also thought that the hull MG mantlet also created a bit of a shell trap by providing a horizontal surface on a steeply sloped front plate.

Is there any justifaction to any of this operator folklore ?

Does the game model the difference in the purported accuracy of the soviet 76 verses the long 50 and 75 to the same level of detail that they model penetration?

Their folklore was that their gun/ammo/sights/rangefinder was less accurate than the germans so they had to get in closer.

I know one concern on the operator side was that the quality of the soviet ammunition was frequently questionable so that the muzzle velocity could change markedly from round to round.

If you have ever handloaded ammo, the point of impact can change significantly if the muzzle velocity changes from round to round due to carelessness or the ammo components not playing well together.

[Mr. Tittles]

Even ammo temp variations leads to variance. So ammo stored in a very hot part of the vehicle would fly different than ammo stored in a cooler part.

[JasonC]

Right, it is all because it was warm.

Instead of talking to a brick wall I thought I'd provide a few CMBB facts to chew over and spin.

Uber StuGs, 30+50 variety, the kind with zero rarity for Kursk offensive (July 1943) IIIG early. Cost in platoons as regulars, 93 points per vehicle, average. 6 lanes, no waiting. At various ranges at the other end, Russian 76mm ATGs dug in to scattered trees, hidden. Sometimes F-22 model (L51, the best), usually ZIS-3 model, sometimes an entire battery (4xZIS-3), usually just 1 gun. Ranges 250, 400 (twice), 500, 600, 800. StuGs facing them, tiny side angle, buttoned. Full default ammo for all sides. 3 runs with different Russian guns, 18 StuGs shot at all told.

167 76mm rounds hit the StuGs. 2 fired by M1936 model at 250m (out of 9 - 1 track hit and 6 bounces as well) were "partial penetration, no significant damage" - the best seen. No penetrations for the other 165, any range, either gun. 14 hits were effective - 4 gun damage and 10 track immobilizations. The gun damage came on gun hits, some upper front hull hits, and in one case by a near miss by HE that landed under the StuG.

A ZIS-3 cannot - not "usually doesn't" - cannot penetrate a 30+50 (not uniform 80) StuG from the front at 250m. The Russian field manuals tell them to open fire at 600m. The F-22 cannot - not usually doesn't - cannot penetrate at 30+50 StuG at 400m. That is the range the Russians told their *45mm ATGs* to open fire. The F-22 was supposed to open fire at 800m.

If an entire battery of ZIS-3s opens at once, the chance of disabling a single StuG is pretty good. But only through track hit immobilization. After they are immobilized, multiple simultaneous hits will scare the crew and make them bail. You need 12 hits on average to cause damage, though sometimes they come early and sometimes they come late, so 15-20 is what you should count on. Forget penetrations.

Did I substitute Elephants in these tests? I didn't have to. Rexford already did.

P.S. If this is all intentional and supposedly historical and BTS stands by every tracer of it, then why does a StuG IIIG (early) cost 93 points?

[ November 15, 2003, 09:15 PM: Message edited by: JasonC ]

[Mr. Tittles]

Whats funny is that the Elephant/Ferdinand DID have a problem with its ammor stowage getting too hot in one of the bins. Hot ammo flys quicker.

[Paul Lakowski]

The Stug-IIIF are produced with 30mmFH + 50mm FH armor which resists like 2.6+ 4.8cm or 7.4. However these were bolted and if there is any airgap developed between [warping] the plates that should shatter the projectile. The result is + 0.24d or 1.9cm additional resistance to a total of 9.3cm RHAe, which limits T-34 76mm AP shell to ~0-900m penetration [½ hits], depending on if theres an airgap or not. The Stug-IIIf own 75L46 gun penetrates T-34 at…..

All hits @ 900m range

½ hits @ 1500m range

¼ hits @ ~ 2km range

However later model T-34s the sloping front side turrets employ 52mm and later 65mm cast armor and should reduce penetration range to ~ ½ hits @ muzzle and ¼ hits @ ~ 700-800m range.

So both statements are true.

[ November 16, 2003, 02:05 AM: Message edited by: Paul Lakowski ]

[Panzer76]

JasonC is at it again I see.

Well, for you new people, look do a search and you'll see that this has been discussed to death, and if Im not mistaken, all JasonC had to back up his claims were AARs, which he could not provide reference to, or was refuted.

And that the StuG is too cheap, is also not excaclty a new topic. But not much will be done with that now, for various reasons. The horse is dead, stop molesting it.

[rexford]

Originally posted by Kozak:

This is probably anecdotal, and not based on real science, but the one serious armour weakness that my uncle mentioned about his experiences commanding the T-34 was the drivers hatch in the front hull.

I don't know whether the hatch itself had less armour than the plate around it to allow it to be opened, but the perception was that it was a weak point. They also had the perception that the Germans aimed at the hatch on a front shot.

They also thought that the hull MG mantlet also created a bit of a shell trap by providing a horizontal surface on a steeply sloped front plate.

Is there any justifaction to any of this operator folklore ?

I know one concern on the operator side was that the quality of the soviet ammunition was frequently questionable so that the muzzle velocity could change markedly from round to round.

If you have ever handloaded ammo, the point of impact can change significantly if the muzzle velocity changes from round to round due to carelessness or the ammo components not playing well together.

thanks for the insights from the Russian side, many of which are new.

When armor has an opening, it creates a weakness due to edge effects and added surface area. Striking near an edge or opening can significantly lower the effective resistance, so the Russian reports are consistent with ballistics. Good point.

The hull machine gun port is going to be a weak point, in the initial combats between Panthers and M10's in Normandy the only M10 penetrations of the Panther glacis were through the machine gun ball mount and bouncers off the mantlet bottom that went through the hull top. Another good Russian point.

Inconsistent powder charges made the U.S. 75mm M72 AP round an adventure in North Africa when Grants fired it against panzers.

Thanks for sharing those notes with us. Anything on how far away from 75mm L43 guns a T34 would have to stay to feel safe?

[rexford]

JasonC,

German reports from 1942 stated that the 75mm L43 penetrated T34's at 1200m regardless of angle, which probably included front and side shots. There were a large number of T34 knocked out, and it is unreasonable to assume there were no frontal hull hits.

On paper, 75mm L43 APCBC should penetrate the side of a T34 well beyond 1600m on a flat-on hit, ditto for the turret front or mantlet on a 1942 T34. So I interpret 1600m max range as the most difficult to defeat frontal area with a limitation based on accuracy.

Yes, CMBB does not give T34 armor the variability that appears to apply, and face-hardened plates in contact are very strong without too much for edge effects. Take it up with the game designer.

Two face-hardened plates in contact provide more face-hardened layer distance than a single plate of the same thickness, and even if there is no air space between two plates I would expect the face-hardened resistance of 32mm/30mm to equal or exceed 62mm.

Here's why there are misunderstandings regarding two plates in contact.

Homogeneous plates in contact resist with less effectiveness than a single plate because the surface of those plates is less restrained by adjacent material and easier to push out of way.

Two homogeneous plates in contact have more low resistance surface area than a single plate with same thickness.

With face-hardened plates the resistance of the surfaces is greater than the interior, so two plates in contact should be more difficult to defeat.

The British tests at Cairo (1942) show PzKpfw IIIH 32mm/30mm resists like 69mm, the U.S. firing tests against Pzkpfw IVG (30mm/50mm) suggest greater than 80mm resistance (with a possibility for less than 80mm), the British experience with 2 pdr and 37mm AP suggests 32mm/30mm resists like at least 62mm if not more.

The March 1943 Tiger report indicates that T34 were "safe" at 1235m versus the panzers they were facing. When a T34 fires at a panzer and the panzer fires back at the tank that shot at it, the panzer gun will be aimed at the turret front of the T34 with no side angle. No side angle at all.

1235m safe range works for 50mm L60, does not seem 100% reasonable for 75L43.

Lorrin

[ November 16, 2003, 09:38 AM: Message edited by: rexford ]

[Jeff Duquette]

Paul said:

The Stug-IIIF are produced with 30mmFH + 50mm FH armor which resists like 2.6+ 4.8cm or 7.4. However these were bolted and if there is any airgap developed between [warping] the plates that should shatter the projectile. The result is + 0.24d or 1.9cm additional resistance to a total of 9.3cm RHAe, which limits T-34 76mm AP shell to ~0-900m penetration [½ hits], depending on if theres an airgap or not. The Stug-IIIf own 75L46 gun penetrates T-34 at…..

This is pretty divergent from your post about a year back on the Yahoo Tankers Forum. I had brought up the air-gap being of some significance on the KV-1E’s bolted on armor. You indicated that this small air gap would have little or no effect on normal AP if the dimension of the air gap was not at least as large as the diameter of the projectile. You than went on to say that these smaller air-gaps might affect the performance of HVAP\APCR. Is there some reason why you are now changing your opinion on this particular aspect of terminal ballistics? Bear in mind we are not talking about analogies to long slender APFSDS. These are big fat, blunt projectiles that would be striking a STUG-III’s armor.

[ November 16, 2003, 11:38 AM: Message edited by: Jeff Duquette ]

[ScouseJedi]

I dont know how relevant this is but relating to air gaps....

If you are cutting a piece of steel with an Oxy acetylene torch and you come across a plate underneath you will not cut through the upper and one below at the same time.

This happens even when the 2 plates are bolted together with no air gap. Even though the upper plate is effectively molten this heat is not adequately/quickly transferred to the plate beneath it.

Not sure how this would relate to effects on armour penetration though.

[Paul Lakowski]

Originally posted by Jeff Duquette:

Paul said:

The Stug-IIIF are produced with 30mmFH + 50mm FH armor which resists like 2.6+ 4.8cm or 7.4. However these were bolted and if there is any airgap developed between [warping] the plates that should shatter the projectile. The result is + 0.24d or 1.9cm additional resistance to a total of 9.3cm RHAe, which limits T-34 76mm AP shell to ~0-900m penetration [½ hits], depending on if theres an airgap or not. The Stug-IIIf own 75L46 gun penetrates T-34 at…..

This is pretty divergent from your post about a year back on the Yahoo Tankers Forum. I had brought up the air-gap being of some significance on the KV-1E’s bolted on armor. You indicated that this small air gap would have little or no effect on normal AP if the dimension of the air gap was not at least as large as the diameter of the projectile. You than went on to say that these smaller air-gaps might affect the performance of HVAP\APCR. Is there some reason why you are now changing your opinion on this particular aspect of terminal ballistics? Bear in mind we are not talking about analogies to long slender APFSDS. These are big fat, blunt projectiles that would be striking a STUG-III’s armor.

The loss of projectile based on properly spaced plates [>1d] should be 1.3d for monoblock and 2.6d for sheathed . With limited space between plates its minus 0.7d so that becomes 0.8d for monoblock and 1.6d for sheathed penetrators.

The loss against AP shot should be 0.1d*V[km/s]...if there is sufficent gap [twice for sheathed] and about 70% of this is there is insufficent gap.

So 76mm @ 600m/s is 0.6d if sufficent gap and 0.42d if not.

Whats new is the system of calculating t/d. I made a mistake assuming AP lost t/d like APFSDS but its less impact.

I've figure that for AP shots its more like

[Thickness* Te) ÷ projectile thickness]÷ 2[semi infinite] ^0.2 .

So 3cm FH @ 10° t/d becomes

(3cm x 1.3[Te FH])÷ 7.6cm ÷ 2^2 or 0.76 x 3cm= 2.28cm @ 10°= 2.33cm

Then 'spaced plate effect' becomes; SQRT [2.33÷7.62] = 0.55* 0.1d*V[km/s]* 0.7[poor gap]= 0.23d or 1.8cm additional protection.

That should mean the driver plate offers

2.33[3cm FH ]+ 1.77cm[space] + 4.3cm =8.4cm...which should limit 76mm penetration to ~ muzzle with gap and ~ 1km without.

I guess I assumed these plates are at 20° angle.Thats why I try to avoid posting such cals...all it takes is one small error

[rexford]

What is the basis for the calculations of face-hardened armor penetration as a function of projectile diameter and plate thickness?

30mm of face-hardened armor (FHA) plate resists like a 30mm FHA plate vs 37mm APCBC and 75mm APCBC, and the resistance at 10 degrees or 20 degrees from vertical would be slightly more than 30mm in both cases.

The calculation that relates 30mm face-hardened plates to 23mm face-hardened resistance vs 76mm rounds is something I have never seen before.

So far we have three bits of info on the resistance of two face-hardened plates in contact, one anecdote for 2 pdr and 37mm vs PzKpfw IIIH front hull, one U.S. firing trial for a variety of guns and ammo vs PzKpfw IV 30mm/50mm and the Cairo tests where different guns and ammo combinations resulted in about the same result.

In no case did two FHA plates in contact resist like less than the total combined thickness.

The photo's of PzKpfw IIIH front hulls that I have looked at over the years do not seem to suggest a 3" air space between plates, which would be more than twice the thickness of the 32mm add-on plate and one would think that it should show up in some picture.

My guess is that the Germans would not allow a 32mm plate with a 30mm warp from straightness to pass inspection. Or even a 30mm plate with a 20mm warp.

So what kind of airspace is needed?

[Jeff Duquette]

Paul:

Thanks for the in-depth explanation. And even more thanks for working through an example problem. What is the “Te” abbreviation?

I would tend to agree with Lorrin on allowable plate camber for the PzIIIH example; particularly over the short span between hard connections that we are talking about with the PzIIIH's bolted on frontal armor. 1.77cm seems like a fairly large non-spec air gap over a span of what?...1 or 2 feet between bolt lines? Even if the exterior plate and interior plates were conected with concavity in opposite directions.

This does however bring the whole question of implied value of additional track blocks...again. The lower front plate of most PzIII’s typically will have an extra length of track draped over it. Not that this has anything to do with the rather rudimentary firing trial data presented in the Cario Tests. However, in actual combat I can easily imagine a 1 or 2 inch air gap existing between the track blocks and main armor.

[A.E.B]

Hi all

The never ending debate on penetration!

I don't have anything to add except for some pictures, target area statistics and one piece of heresay.

A friend of mine used to command a ADF Leopard 1 (currently he commands a desk). He once showed me a ADF booklet that listed a number of enemy AFVs, their gun/performance stats and the "survivability" of the Leopard 1 verse each of those AFVs (who kills who at what range). His comment was that you could easy adjust those figures by 25% +/- on the battlefield, and that he didn't intend to consult the book during battle!

By my quick calculation, these are the relative target areas of a T34/B front on.

Turret 14.5%

Upper Glacis 42.5%

Lower Glacis 17.5%

Track/Suspension 25.5%

The weakpoints make up

Driver's hatch 3%

Mantle/Flat turret front 6% or 41% of the turret front.

Hull MG mount 2.5%

Turret ring shot trap 3.5%

Or 15% of the total target area.

The above assumes a front-on profile (zero degree) with no hulldown.

By my quick calculation, these are the relative target areas of a Pz IV F2 front on.

Turret 22.5%

Upper Glacis 36.5%

Lower Glacis 22.5%

Track/Suspension 18.5%

The Mantle is 5.5% of the total, or 25% of the turret front.

The Upper glacis is split between the flat crew plate and the slopped lower plate.

Upper front glacis 14.6% of target area.

Lower front glacis 21.9% of target area.

The weakpoints make up

Driver's port 2%

Mantle 5.5 % (this may not be a weak spot!)

Hull MG mount 1.5%

Turret ring shot trap 1.5%

Or 10.5% of the total target area (5% without the mantle).

Again the above assumes a front-on profile (zero degree) with no hulldown.

So what does this tell us? That the T34 turret is a far smaller target as a percentage than that of a Pz IV F2.

Non-hulldown, a T34B would be hit in the turret 14.5% of the time vs. 22.5% for the Pz IV.

If Lower-Hulldown (no track or Lower Glacis) then the T34B is 25.5% like to be hit in the turret vs. 38% for the Pz IV.

The weakspots on a T34B make up 15% of a non-hull down T34B and 26.5% if Lower-hulldown.

The Pz IV F2 by comparison 22.5% likely to be hit in the turret face (its weak spot) with 5.5% being the mantel. Lower-Hulldown the Pz IV F2 is 38% likely to be hit in the turret face with 9.5% hitting the mantel.

These shot percentages only work for rounds aimed at and varying around the center of mass - if aiming is possible then hit distributions will change.

I couldn't be bothered to do the above stats for the STUG III F/G.

Has anyone ever seen the German Flakpanzer T34 ® before? I think that only one was built?

T34 in German service

Regards

A.E.B

[ November 17, 2003, 12:15 AM: Message edited by: A.E.B ]

[Paul Lakowski]

Originally posted by rexford:

What is the basis for the calculations of face-hardened armor penetration as a function of projectile diameter and plate thickness?

So what kind of airspace is needed?

THe basis of all modern ballistics test are semi infinite reference point...this is the only way to compare differing levels of resistance etc. The task is then to back calculate the t/d effect etc.

Angled impact is controled by projectile nose design, since this controls the back plate effect.

As to the airgap it doesn't take much to allow shatter to occur, remember the case of the 90mm HVAP shot hitting two plates that were treated as one in the test. Should have penetrated cleanly but ended up shattering inbetween the plates.

Now that I've had a chance to review this I need to make a correction.The formula was developed from APFSDS back through APDS to AP penetration and in all my modern cals the 'te' is factored independent of t/d so thats in the wrong place in the forumla I put down. It should read...

[Thickness) ÷ projectile thickness]÷ 2[semi infinite] ^0.2 * Te.

So 3cm FH @ 10° t/d should become

3cm÷ 7.6cm ÷ 2^2 x 1.3[Te FH]or 0.723 x 3cm x 1.3 = 2.82cm @ 10°= 2.9cm

Then 'spaced plate effect' becomes; SQRT [2.9÷7.62] = 0.61* 0.1d*V[km/s]* 0.7[poor gap]= 0.26d or 2cm additional protection.

That should mean the driver plate offers

2.9[3cm FH ]+ 2cm[space] + 5.2cm =8.1=>10cm, depending on if the plate bulges or not during impact.

Jeff 'Te' means 'thickness effectiveness' and the + 2cm is the reduction in penetration due to the airgap. If this air gap was 1d or more [iE 7.6cm] it should result in + 2.8 cm loss in penetration.

Against higher velocity GErman 75mm guns this type of applique mounted on a KV-1 should mean higher loss due to higher velocity.However with APCBC ammo you have the possiblity that the sectioned nose will truncate the damage done to the penetrator by such spaced plate limiting the loss of penetration...that and the fact that these are longer penetrators which lead to more penetration anyways.

[ November 17, 2003, 12:15 AM: Message edited by: Paul Lakowski ]

[Redwolf]

Thanks for the numbers. Just one point:

Originally posted by A.E.B:

Non-hulldown, a T34B would be hit in the turret 14.5% of the time vs. 22.5% for the Pz IV.

If the area is 22.5% of the surface then the chance to hit it is not 22.5%. There is a bell curve based on the distance of the impact point to from the aimed point. Or is other words, the farther away from the target point a given square centimeter is the less chance to hit.

If I knew the front angles of T-34s are in question I would have measured the one in Munster two weeks ago

[A.E.B]

Redwolf

Of course the actual surface area available changes with every small permeation in facing and inclination.

I am leaving the determination of just what the 75/L43 vs. 76.2/L42 could penetrate at what ranges as I don't have access to the required data.

But it is not only a matter of whether one tank could penetrate the other at range, but the raw chance of striking an area that could be penetrated.

My area figures merely show (ignoring the chance of a hit) the relative target areas of a T34B vs. a Pz IV F2 in a straight head-to-head shoot out.

Basically, the soft areas of each tank (i.e. the areas that can realistically be penetrated) are the important factors - not the areas that cannot be penetrated.

If a Pz IV F2 is capable of penetrating the T34B weak spots at a range of say 1,000 meters, then any shell that hit front on has roughly a 15% chance of striking such a weak spot.

In return the T34B is capable of penetrating the Pz IV F2's turret front or weak spots at the same range, then that T34B has a 25% chance of striking such an area.

Even in the worst case, the turrets of both tanks must be face-on if they are firing at each other, regardless of hull down or hull orientation. Then the odds are 6% for the T34B to 22.5% for the Pz IV F2 of hitting the area of the turret face that can be penetrated.

Given the above, you then have to consider relative gun accuracy (# hits as a percentage of shots fired) and the ROF to see whether it was worth the average Pz IV F2 taking on a T34B at range.

Example: ROF x % hits likely x % chance of hitting a weak spot.

Reality of course is far more complex!

Regards

A.E.B

[ November 18, 2003, 12:58 AM: Message edited by: A.E.B ]

[c3k]

Gents,

As always, very interesting. I'd like to add some emphasis to a few points and see if the various grogs care to develop them.

The driver's hatch on the T-34 glacis would seem to be a true weak point - both anecdotally and empirically. It also makes up a rather large area of the central zone of the glacis. Would that area not be specifically targetted by the Germans?

Aimpoints seem to be somewhat important. Gunners aim at center of mass, _unless_ there's something more visible, or even better more visible AND located near a weak spot. (Soviet Hinds in Afghanistan - oil cooler near red star; U.S. M113's in Vietnam - white star in center of side armor; German adaptation of balkenkruz (sp?)(+) by painting out the center portion because it was used as an aimpoint.)

My point? What's the penetration data for various German guns which achieve hits on or very close to the T-34's driver's hatch? What is the ability of the various German guns to hit an aimed point? What is the shape of distribution of hits of German guns vis a vis Soviet guns?

If a T-34 must aim at center of mass and its hits land in a random scatter around that aimpoint, that would be less effective in penetrating than would a German gun which aims at a weakpoint and achieves a tight shot pattern centered on that aimpoint.

(Edited to repair basic grammatical errors.)

Regards,

Ken

[ November 17, 2003, 09:09 PM: Message edited by: c3k ]

[Jeff Duquette]

Paul:

I have a couple of additional questions I am hoping you can wade through. After looking at your write-up a bit closer I realized you are not saying the minimum air-gap would have to be 1.77cm.

1) What -- if any -- modifications would occur to the spaced armor modification if the plates were some other steel combination…say RHA skirt over RHA main armor instead of the FH over FH which is being considered in this example?

2) Why is the air-gap advantage applied to the thickness of the skirting plate? Why isn’t the thickness of the main plate employed in determining the spaced armor added advantage?

3) You have specified an optimal air-gap space of >1d. Is there any added advantage if the air-gap is say 1.5d or 2d or 3d. The way in which you have presented your equation, the spaced armor advantage is purely a function of:

The skirting plate thickness;

Projectile diameter; and

Projectile striking velocity.

Is there no added advanatge for an air gap wider than 1d?

4) Along the same lines as Question 3 except in the opposite direction. You have indicated that anything less than about 1d would fall into the range of less than optimum spacing. However you have really not established a lower bound. Is there a point at which no real spaced armor effect would occur. Are we talking 0.1d or 0.5d; or will an air gap equal to the width of an oxygen molecule be sufficient to rate a spaced armor advantage? ;o) Regarding the 90mm HVAP example cited, the warping resulted in a 2-inch airgap. This is about equal to the diameter of the M304's penetrator.

5) Just to clarify in my own mind…your final assessment of the Stug-III armor you indicated: 2.9cm + 2cm (air gap) + 5.2cm = 8.1cm => 10cm

The 5.2cm is derived from: ((5cm/7.62cm/2)^0.2)*5cm*1.3….is this correct.

Thnx

[ November 17, 2003, 06:40 PM: Message edited by: Jeff Duquette ]

[Paul Lakowski]

Originally posted by Jeff Duquette:

Paul:

I have a couple of additional questions I am hoping you can wade through. After looking at your write-up a bit closer I realized you are not saying the minimum air-gap would have to be 1.77cm.

1) What -- if any -- modifications would occur to the spaced armor modification if the plates were some other steel combination…say RHA skirt over RHA main armor instead of the FH over FH which is being considered in this example?

2) Why is the air-gap advantage applied to the thickness of the skirting plate? Why isn’t the thickness of the main plate employed in determining the spaced armor added advantage?

3) You have specified an optimal air-gap space of >1d. Is there any added advantage if the air-gap is say 1.5d or 2d or 3d. The way in which you have presented your equation, the spaced armor advantage is purely a function of:

The skirting plate thickness;

Projectile diameter; and

Projectile striking velocity.

Is there no added advanatge for an air gap wider than 1d?

4) Along the same lines as Question 3 except in the opposite direction. You have indicated that anything less than about 1d would fall into the range of less than optimum spacing. However you have really not established a lower bound. Is there a point at which no real spaced armor effect would occur. Are we talking 0.1d or 0.5d; or will an air gap equal to the width of an oxygen molecule be sufficient to rate a spaced armor advantage? ;o) Regarding the 90mm HVAP example cited, the warping resulted in a 2-inch airgap. This is about equal to the diameter of the M304's penetrator.

5) Just to clarify in my own mind…your final assessment of the Stug-III armor you indicated: 2.9cm + 2cm (air gap) + 5.2cm = 8.1cm => 10cm

The 5.2cm is derived from: ((5cm/7.62cm/2)^0.2)*5cm*1.3….is this correct.

Thnx

That is correct.

For example 37mm Vs 45mm SHS of T-34 glacis is [45mm/37mm/2 ^0.2]*1.2 or 49mm @ 60°...while if 75mm hits thats

[45mm/75mm/2 ^0.2]*1.2 or 42mm @ 60°.

# 4) I did wonder about that but the shattering was severe as I recall not minor.In anticipation of that very question I was reviewing some of the ballistics experiments. In one very involved study hard Steel short rods with sharp ogives were test fired into hugh blocks of aluminum. The actual aluminum penetration was easy until it hit the next block placed adjacent to the first. Either the penetrator veered off at 45° after crossing the boundry or it shattered! In similar modern long rod penetration studies against steel the blocks surface of both exited block and reentry blocks were severly distorted showing massive expenditure of energy. Layering in modern ballistic armor is expected to yeild anything from 10-40% improvement in the overall armor resistance. There is a direct connection some where here but I have still not been able to quatify that.

#3) this is not easy to answer since the damage effect on penetrator is determined by the spaced plate ...and when breaking it down it works best if you make that simple distinction.VEry large gaps tend to increase the overall resistance of long rod penetrators or even short rods @ > 1km/s impact velocity to the tune of 10-20%...but these are over vcery large gaps of 20 diameters. I recall Zukas did a paper that for 10:1 L/d rods @ 1.5km/s the gap increased dramatically when the gap got to 3-4 diameters. On the other hand Holher and Stilp show that below 1km/s impact V, short rods penetrated more than two thinner plates easier than one thicker plate when the air gap was 20 diameters. I tend not to factor large airgaps in.

#3) where large airgap becomes significant is in the area of shaped charge resistance. The formula is

The erosion of the skirting plate plus the base armor [minus t/d] and the standoff effect plus 0.7d...so if the skirting plate is 1cm mild steel and the warhead is 10.5cm that adds upto 8.1cm plus the standoff effect[depends on liner material etc].

2) because its all got to do with how much damage the skirting plate does to the impacting penetrator...remember Dr Elders paper on "spaced armor at sea", if the damage was insufficent to decap the APCBC the projectile could contiue to travel 24 diameters airgap and still penetrate with almost full effect.

For example the steel mesh the germans employed is perforated plate armor and should increase the damage to the impacting projectile by 1.6 times [and double that if its a HVAP shot]...that explains why those 14.5mm HVAP shattered and did almost no damage to the Pz-III hulls....it literally shatters the penetrator!

1)If it was straight steel there would be no 1.3 modifier at the end and it would resist less. Additionally if the skirting plate was aluminum its Te is ~ 0.3 to 0.4, so you'd need three times as much thickness skirting plate.