Alvaro

Hola Alejandro. I have this book from W. Fleischer, English version of the originally German book, but although I read the whole book, I have never seen that excerpt you mentioned. Can you tell me the page it is mentioned? Best regards

It is possible to make short tests of a new projectile at a given strive velocity to obtain the projectile/plate constant required to fill some ballistic equations, DeMarre, ArtKom, etc. and predict penetration at other velocities and sometimes… even at other angles of attack . The accuracy of these mixed tested/theoretical curves is good provided the penetration mechanics remain the same, which is not always the case. For example if ArtKom curves where made for AP(BC) projectiles against very hard test plates, surely those projectiles would break in some extent at impact. (I never seen a test of uncapped projectile to remain intact against very hard plates). But if these same projectiles where tested again softer armor, perhaps they remain whole and then ArtKom equation become pessimistic. If this was the case, Russian penetration figures would be worst case ones with room for improvement when projectile damage was minor. Best Regards Alvaro

Mobius, yes, this is the exact transcription. But it seems more logical 103 instead, as an 3 can be mistaken more easy with 8. Regards Alvaro

Hi Jeff: Although I think it is the same report you know, author is Colonel Michelet, but it is not from Saumur and it was not recovered by Frederic, but by another French man. It seems he (I just cannot remember now his name) got it directly from Col. Michelet!. It seems that the source of this and other French penetration data was British, at least this is what a friend, retired French Armor colonel, said to me when we joined and commented this report last year. It has sense, because ovbiously French could not make firing tests during the war. Of course we may be wrong. At the time this report was done only Pzgr39 was available. Alvaro

French post-WWII military publication ("Notice sur la DCA dans l'aemee allemande) from British data: Paz. Gr. m. Bd. Z. penetration data: meters...velocity..90º...60º 0...........793.......141...118 457........748.......130...110 914........703.......119...108 1371......658........109...94 1828......617........99.....87 2285......577........90.....80 Weight: 9.5 kg MV: 810 m/s Charge: 2.420 For comparison, Pzgr39 was listes as: Charge: 2.950 Weight: 10 kg MV: 800 m/s

Here are some data from ADM 213/951, "German steel armour piercing projectiles and theory of penetartion" which may help: Special plates ware made for proof and trial purposes. It was found that the plate made for tanks (...) was too hard and apt to break up against repeated attack." Krupps made the majority of the special "trial plate", with a rolling tolerance of 2%. Test plates were not previously calibrated, except for very important trials. The distance between shot holes was 2.5 calibres. At least a given* number of rounds with the narrowest possible range of velocities must penetrate the plate (projectile throught) in a condition fit for bursting. The higer velocity value obtained will be considered as the Gd value: It is the velocity at which the projectile just penetrate the plate with no remaining velocity. *Number of rouns required depends on caliber: 20-37mm : 10 rounds 75-88mm 5 rounds Also, it was obtained in a identical way the maximum velocity that gave complete protection (Gs). From this paper it seems that Germans only considered success when the projectile completely penetrated the plate, INTACT. Best regards

T-54 turret front 200mm cast, curved Range m /theorical pen. mm @0º PaK43 /600 /220 100mm D10 /500 /162 T-34 85 turret/mantle 90mm cast, curved Range m /theorical pen. mm @0º ZIS-3 /250 /81 Pak40 /1000 /105 85mm /1000 / 85 ZIS-2 /600 /103 Sherman M4A3 turret/mantle 90mm cast, cuved Range m /theorical pen. mm @0º ZIS-3 /350 /79 Pak40 /1000 /105 85mm /1000 /85 ZIS-2 /900 /97 Let’s assume for a while, in order to simplify, that cast curved armor had the same resistance to penetration than flat RHA. Because target is common, is possible to make some comparisons between these guns and therorical claimed performance: (rounded values) Pak43: -10% Pak40: -15% (T-34), -15% (Sherman) 100mm D10: +20% 85mm: +5%(T-34, +5% (Sherman) ZIS-3: +10%(T-34), +12% (Sherman) ZIS-2: -13% (T-34), -7% (Sherman) If curved cast armour had less resistance than flat RHA, then just add that value to all that percents. So that, what do you think? Can you find a way to explain all this? Perhaps late war German ammunition performed worse than expected? And why Russian ammo were usually understimated?, if they were. Best regards

It is from Bojan post on Sherman data: Best regards

I am wrong. 88m PAk43 against 100m RHA T-54 (200mm LOS) compared with 200 cast curved front turret. Here sloped armor is quite effective. Best regards

In Zaloga's New Vanguard Sherman book appeared with a flat mantle, like this... http://www.armchairgeneral.com/photopost/d...ankfest_602.JPG But perhaps Bojan can tell us which is the Yug. Sherman Ah! I see that Bojan posted at the same time than me.

Let me make an observation. Sherman turret front is cast 90mm thick while its glacis is RHA 64mm@47º that represents a LOS of 94mm. T-34 turret front is also cast 90mm thick (curved) and LOS of RHA glacis of 90mm also. So it seems possible to compare thick plates (turrets) against the same LOS of sloped plates (glacis) Well, comparing the penetration ranges for both turret and glacis forT34 and Sherman, it seems that thick vertical plates have a slight advantage over sloped plates for every gun except ZIS-3 against Sherman. This difference is increased if we considered that cast armor is said to be less resistant than RHA. ZIS-2 against Sherman has identical penetration range for both turret and glacis. And as Bojan pointed, T34 armor is more effective against ZIS2 than Sherman. It looks like sloped armor is less effective than equivalent weight of vertical armor against projectiles of larger calibre than its thickness. When caliber and thickness are similar, ZIS2 against Sherman glacis, sloped armor is neutral. There no example here of small caliber guns, but I assume that in that case sloped armor would be better than vertical. And also in that case hard armor is better, as ZIS2 seems to indicate. What do you think? Best regards Alvaro

Jeff, I didn't have contact with him and I don't know whether he will publish the book he said he was preparing. Best regards Alvaro

Hi Jeff: I don’t see any reason for irritation here . I do not pretend to convince anybody. I am just trying to share my opinions. Perhaps my English is not good, but please, do not answer to what I didn’t mean. I never defended, and neither do it now, hypothesis of flawed T-34 armor plates, turret ring hits, etc. T-34 was a success, no doubt about this. And not only was well designed from the classic firepower/protection/mobility triangle, but also from a strategic point of view of easy mass production in a country with quite less industrial power than Germany, for example. Prior WWII, France was a leader in armor technology and research, which was halted during German occupation, of course. So it is reasonable to think that technical publications of French Army just after the war reveal just their knowledge in 1940. They knew what happens when armour hardness was increased up to very high hardness levels. They knew that the perforation limit had two maximum levels for a given plate/projectile. One in the range of, let’s say, normal hardness and the other in the range of very high hardness. Between them there was a drop in the perforation limit. What I say is that French knew that very high hardness armor had similar perforation limit than normal hardness armour. Also they knew that the protection limit of the armour, where there is no internal damage from projectile/spalling, was optimum in the normal hardness range. But when the hardness was progressively increased, the protection limit decreased also progressively, without any improvement in the very high hardness range. So, it is possible that Russian designers also know this in 1940 and chose high hardness armour because was easier to produce for them, with the only drawback of more spalling, and the same perforation limit as normal hardness armour. Or perhaps you are right, and high hardness armour at high angles of attack was even better that normal hardness armour. If so, then why to make the whole turret and hull sides also of high hardness armor? They were not very much sloped… Best regards Alvaro

Hi Jeff: Yes, I agree that T-34 was designed from the beginning to withstand 37mm guns at any range and 76mm at 1000m. But also, it was designed from the beginning to be cheap and easy to manufacture tank in large numbers, as during its desing phase in Russian the war was considered inminent. High hardness plates were well studied before the war. And I am nearly sure that the relation between tempering temperature, hardness, ballistic limit and protection limit was not a secret for WWII designers of any power. If T-34 armor was a bit less hard it would be at least so resistant to 37mm guns, as less prone to spalling. Memories of T-34 tankers also talk about the spalling of their armour. So it must be any design reason to make it very hard. KW tanks were not designed by the same team and followed a different path. They begun with thick plates at moderate hardness, classical style, but later, the following design, IS tanks went to thick plates but very high hardness. Why? After the war this practice was abandoned, it seems. Russian tanks designers worked in competitive teams of several projects al the same time. At the end, the best will be selected for production in a comunist state. So their points of view surely were different than the others. They had to make tanks that were easy to be produced with limited technology, in big numbers and at the same time perform well. In that situation some have to be sacrified to succeed. Best regards Alvaro

Reported hardness of 350 BHN for T-34 85 is not too much for Russian T-34 standards. That hardness level even fails into German early war specifications for 30-50mm test plate thickness: 323-368 BHN. It is also possible that during late war T-34 armor reduced its hardness level, I don't know. Anyway, both 90mm cast mantles of Sherman and T-34 were penetrated at the same distance with PaK40 AP ammo, 1000m in these tests. And here hardness difference is very big. I suppose that high hardness armor, because it required lower tempering temperature, was easier or faster to produce. And softer armour was less prone to spalling. And perhaps also requeriments of aleations of strategic metals were different. What I mean is that the thinking behind of armour characterists was not only based upon prenetration resistance and other factors may had a place here. Best regards.