Why KV has "very low" chance at 90 meters to PzIII?

[Guest Mike]

Well thank you mister Bastables for all that insightfull info.

Since you apparently know it all why didn't you just say so in the first place?

[Hortlund]

Originally posted by Denizen:

The Spaced armor on the front hull and turret was indeed better at resisting the 122mm soviet APBC than the sloped armor of the panther's front. Soviet gun tests during and after the war would show that while the 122mm APBC could penetrate and travel all the way through the Panther from the front, it would barely harm the Pzr III.

First, the spaced armor on the PzIII might have been better at resisting the Soviet 122mm APBC round on a mm by mm penetration-calculation-basis. But this does not translate to PzIIIs being more surviveable on the battlefield. The PzV has very sloped front armor, the effect of such high angles is not only that enemy shells have more armor to penetrate, it also increases the probability that the enemy shell will richoshet (sp) either completely (i e deflecting away from the tank), or partially (i e some kinetic energy is spent when the impact force changes direction).

Second, I would love to see your sources on that penetration data. I hope you are not using the "Report on the results of testing of the 100mm and the 122mm tank guns at the KUBINKA proving grounds" from 1944? Because if you do, you should know that the Panther tank used as target was of poor quality, and the test results are dubious at best. If the results actually happened, then the Panther tank used as target had armor defective enough to be only 85% of "normal" armor.

Consider the source...suppose you are on the staff of the armaments production facility, what report is more likely to get your butt shipped to a Gulag?

"Yes comrade Stalin, our armamnets are seriously deficient and this is probably why we are suffing sometimes 10 to 1 losses to Facsists"

or

"Yes comrade Stalin, our tanks are clearly superior to the Fascists and able to kill them to nearly the limit of their effective range. The losses at the front must be do to poor tactics in the untrained ranks."

Having said that, the 122mm APBC round was the best AT round the Soviets used in ww2. Lets do a test fire against a PzV. The PzV front had 80mm armor at 55 degrees slope. First, armor penetration is not a step function where penetration fails if you are a mm short and is not assured if you are a mm over. It can occure anywhere down to .85 pen/armor and can fail up to 1.15 pen/armor ratio.

So how do you get the armor ratio? The actual "effective armor is a function of thickness to diameter ratio and the above estimates of effective thickeness are based on the (base/(cos(angle))^1.4) estimate.

The PzV glacis is 85/55 of varying quality. This means a variance from a bit over 200mm equivalent to 150 or so for a T/D ratio of .7.

The early 122mm had a penetration (50% probability or deformation of backing plate vs BHN 250 RHA) of about 189mm. The later model of the 122mm was improved to about 206mm.

This all means that the PzV glacis was potentially vulnerable anywhere from 0 to about 1200m range when being shot at by a 122mm gun using APBC ammo. (the 0 figure above indicates that in some instances, the 122mm gun could not penetrate PzV front armor from any range).

(source:Bird and Livingston, WW2 Ballistics)

Now, I dont have the numbers for the PzIII armor readily avaliable here, so I cant make the same calculations for the PzIII.

[...] since combat records indicated that the later variants of the Pzr III were still very much a threat to all exsisting soviet tanks by virtue of the spaced armor as well as the schurzen protection enveloping the hull and turret.

Strictly speaking, this does not make the PzIII a threat to "all existing Soviet tanks", it only makes the PzIII a less threat to its own crew. And Schurzen doesnt really help that much against AP or APBC ammo. Schurzen was designed to detonate HEAT rounds outside the main armor. The effects on AP or APBC rounds are slim.

Where availible, tungsten ammunition providied the 50mm gun of the Pzr III with all of the anti-armor performance of the Panther in a smaller, cheaper, and more efficient package.

First, the key phrase here seems to be "where avaliable". Tungsten rounds became increasingly scarce in Germany from 1942 on. After the loss of the Donbass region (the area around Dniepropetrovsk), Germany had extremely limited access to rare minerals, and those they could get their hands on were often used in other parts of the German war industry. The most likely scenario would involve a PzIII entering the battlefield with one or two rounds of APCR max, and the rest being normal AP. Best case scenario would see that same PzIII with 4-7 APCR. If you want to do a fair comparrison you should compare the standard AP of the 75mm KwK 42 L/70, with the standard AP for the 50mm KwK 39 L/60.

(Standard AP for 50mm at 100m=67mm)

(Standard AP for 75mm at 100m=138mm)

or, why not compare APCR penetrations, just for fun...

(standard APCR for 50mm at 100m=130mm)

(Standard APCR for 75mm at 100m=194mm)

These figures speak for themselves.

in terms of overall performance and efficiency, it,[PzIII] and not the Panther, was perhaps the superlative AFV of the Axis forces, as realized by the Russians who fought them.

Lets just say that I question this conclusion.

[ September 05, 2002, 09:30 AM: Message edited by: Leutnant Hortlund ]

[Redwolf]

In addtion to what Hortlund wrote, the Panther glacis had -in practice- a substancial problem with completely cracking open.

A high-quality steel front on a Pz III certainly beats a cracking Panther front. But I fail to see how that can lead to assume that continued production should be done on the Pz III, since you cannot choose the steel available.

[John Kettler]

Leutnant Hortlund,

As has been pointed out repeatedly on the CMBO board, the skirt armor was fitted not to defeat HEAT, though it did as an unintended side effect, but to stop the Soviet 14.5mm antitank rifle projectiles. Evidence produced to support this includes eyewitness accounts of the meeting where Hitler issued the orders.

Regards,

John Kettler

[Hortlund]

Originally posted by John Kettler:

Leutnant Hortlund,

As has been pointed out repeatedly on the CMBO board, the skirt armor was fitted not to defeat HEAT, though it did as an unintended side effect, but to stop the Soviet 14.5mm antitank rifle projectiles. Evidence produced to support this includes eyewitness accounts of the meeting where Hitler issued the orders.

Regards,

John Kettler

Granted.

I suppose I could have been more clear in my statement. What I meant was that Schurezen had very limited protection effect on "normal claiber" AP rounds (with all the variants) and relatively good protection effect on HEAT rounds.

[Mattias]

Welcome to the discussion Hortlund

This general subject, armour, projectiles and their interaction has been a hot topic for about as long as this board go back, which would be, what, early 1999. Far from wanting to discourage you I just want to say that you are in good company with regards to this particular field of interest

You might want to look for threads involving one "Rexford" (member number 4402) for a host of interesting discussions on the subject. A search on that name on the CM: Beyond Overlord forum yields a number of threads for example, searching on the member number even more I guess. If nothing else he is more often than not where the discussion is.

As I recall the nature of the Panther glacis is *the* most frequently discussed subject of all.

- On the subject at hand I might add that the penetration figures given for the 50mm tungsten rounds did not translate into real world performance, for a number of reasons. Lack of availability was one thing, the inferior long range capacity another, as I recall it lower damage potential has been mentioned and I have most definitely read that the Pzgr. 40 suffered from atrocious rates of case expansion, leading to the crews refusing to use them. I'll have to look for the sources but they are around

M.

[Bastables]

I'll get you started mate.

From a report 31 July 1942 Pz regt 33

‘The Panzergranatpatrone 40 is no longer fired by the crew because with each round the shell casing sticks or the shell casing ruptures in the gun. This can only be cleared from outside the Panzer by knocking the shell case back out with cleaning rods. Shell casing ruptures occasionally occur when firing the Panzergranate 38.’(1996 Jentz Pg243).

[Hortlund]

Originally posted by Bastables:

I'll get you started mate.

From a report 31 July 1942 Pz regt 33

‘The Panzergranatpatrone 40 is no longer fired by the crew because with each round the shell casing sticks or the shell casing ruptures in the gun. This can only be cleared from outside the Panzer by knocking the shell case back out with cleaning rods. Shell casing ruptures occasionally occur when firing the Panzergranate 38.’(1996 Jentz Pg243).

Wow...

This is the first I have heard about such problems for the APCR rounds. You learn something new every day

I'm assuming that you are talking about the 50mm version of the pzgr 40 here? Do you know if this problem was limited to the 50mm version of the Pzgr 40, or if the 37mm and 75mm versions had the same problems?

[ September 06, 2002, 05:14 AM: Message edited by: Leutnant Hortlund ]

[K_Tiger]

Some days ago, i read elswere on the net about this testing prozedure and the russians stated the front hull armor hade 85 mm.

I will not say, that the JS2 was a bad tank, but i have some trouble to think he was so good like those tests make me belive.

A giant and long gun in a comparable small turret, no changes in the hull design. If we see how many efforts the germans made to put the long 88 on a tank and how big those turrets and casings were to reach a optimum gun plattform.

Im still skeptical about the overall performance from the JSII.

[Bastables]

Originally posted by Leutnant Hortlund:

The Reports contained in Jentz don't even talk about 3,7cm gun at all because it was no longer extent in '42 PIII/PIV armed regts.

The 7,5cm does not seem to have received Pzgr 40 at all although mention is made that the early 7,5cm L/43 Pzgr 39 cases would some times not eject and stick in the breech. Spielberger has reports of the same problems with the gun when early StuGs StuK 40s were demonstrating for Hitler.