Saturday, 10 October 2015

World of Tanks History Section: a 122 mm Argument

The use of IS-2 tanks is one of the most interesting topics in the history of the Great Patriotic War, but it is still not explored very thoroughly.

The IS-2 was the most numerous heavy tank of WWII, and a revolution in both Soviet and worldwide tank building. A real "universal soldier", capable of completing a wide range of objectives, proving itself both in the open field and in the city, lasting for half a century in various armies.

On October 31st, this tank will turn 72 years old.

A hero's portrait

In the spring of 1942, GABTU launched a program to develop a 30 ton heavy tank. Chelyabinsk engineers were tasked with this job. The vehicle was named KV-13, but the index IS-1 almost immediately came into use. Despite the designation, this design had very little to do with the KV-1.

During trials in the fall of 1942, the KV-13 showed an excellent speed of 56 kph, but also revealed many design defects. The process of correction began, as a result of which the mass was increased to 38 tons and the crew grew to 4. By the spring of next year, the IS-1 (Iosif Stalin) index was officially attached to the tank.

The IS-1 was designed to carry a 85 mm gun, but few tanks were produced with one. At the same time as the IS-1 entered development, engineers led by artillery designer F.F. Petrov explored another topic, which proved pivotal in the tank's fate. Their task was a 122 mm tank gun. A design was ready in the summer of 1943, a prototype was completed by the fall, and then gunnery and mobility trials were held. The first 35 IS-2 tanks with a 122 mm left assembly lines in December of 1943. In total, 3385 of these tanks were built during the war, with some design changes.

The majority of IS-2 tanks were sent to Guards Heavy Tank Breakthrough Regiments. In total, 25 units in the Red Army used these tanks.

Against Tigers of all breeds

The purpose of the new Soviet tank had much in common with that of the German Tiger. IS-2 regiments often served as reinforcements of other tank units. Despite some opinions, IS-2s fought Tigers fairly often, usually with a very poor result for the latter. While there was no direct order preventing German tankers from engaging the IS-2, documents starting from the second half of 1944 and until the end of the war frequently mentioned that the enemy strived to avoid contact with Soviet heavy tanks.

The Lvov-Sandomierz operation is characteristic of the use of the IS-2 in battle. From July 16th to July 19th, the 29th regiment destroyed 23 Tigers and Panthers, at the cost of three burned up tanks and eight more that were recovered, five of which were repaired. During the course of the entire operation, the 29th regiment destroyed 38 German tanks and SPGs, losing 4 IS-2 tanks permanently and needing major repairs for 5.

The 71st Guards Heavy Tank Regiment also worked well in that operation. Things started out poorly: the regiment was ambushed, three tanks were lost and three more knocked out, the regimental commander was fatally wounded. In return, the Guardsmen destroyed a Tiger, a Ferdinand, and knocked out two Panthers. After the battle, 18 nonpenetrating hits from 75 mm shells were counted on the armour of one of the tanks.

The regiment encountered another ambush at Mageruv, but this time it was the Germans who had bad luck. The regiment bypassed the ambush without losing a single tank, and Guards Lieutenant B. Slunyaev's single remaining tank destroyed a Ferdinand, two AT guns, and as many APCs. Then the regiment crossed the San river and reached the pre-war borders of the Soviet Union.

Already in Poland, the regiment encountered King Tigers, the latest German heavy tank. Many know the battle where Lieutenant Oskin destroyed three of these tanks, but Oskin was supported by fire from everyone around him. The IS-2 tanks fought with King Tigers one on one. Near Ogledow, IS-2 tanks from the 71st regiment won the battle with a score of 6:0.

Red Army Draught Horse

Aside from breakthrough regiments, some IS-2 tanks were sent to Guards tank brigades. Unlike regiments, these units were heterogeneous. For instance, the 57th Guards Tank Brigade received 10 IS-2 tanks in addition to its T-34s.

The tactics in battle were similar to the use of breakthrough regiments. IS-2 tanks followed T-34-85s, clearing the way for its medium comrades, destroying enemy tanks and SPGs from long distances.

Over nine days, the 57th Guards Tank Brigade destroyed 19 tanks and 12 SPGs, losing four IS-2s irreparably. A heavy tank commanded by Junior Lieutenant Neelov dealt with three German tanks, two SPGs, seven guns, and about a hundred soldiers in the span of one battle. 16 hits were counted on its armour after battle, none penetrated.

In the city, IS-2s fought in assault groups. Their powerful cannon was a great way to destroy German fortifications and emplacements in houses.

Regardless of the part of the front or terrain, IS-2 tanks were always in the hottest spot on the battlefield. Sadly, there is not a single book focused on their use in battle. Starting from the spring of 1944, it's hard to find even one large engagement that did not hear the blast of 122 mm guns.

Original article available here.

27 comments:

  1. After reading this, i am rather unsure.

    Was a IS-2 ever knocked out by a german tank?

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    1. I don't know why you would think that it wasn't.

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    2. lol.
      Thats like saying you dont why the nazis were racists.

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  2. Interesting observation about the IS-2 mod 1944's armor in a War_Thunder review:

    https://www.youtube.com/watch?v=f1_qvmVhMr

    This review confirms what I had measured from a Steven Zaloga book, about a IS-2 mod 1944 in Berlin (tank 441) that was knocked out by a Panzerfaust hit in the side of the turret, causing an internal explosion that blew the gun mantlet halfway down the gun tube. Using a crude scale based upon published dimensions of the IS-2, I measured the edge of the mantlet at 110 mm and the center of the mantlet at over 200 mm.

    This review says that:

    a) the center of the mantlet (with no armor behind it) was 200 mm or more, just as I had measured;

    b) both edges of the mantlet overlap turrent armor, which is itself 100 mm, making the combined thickness in that region in the 180 mm - 220 mm range.

    c) As for the non-mantlet turret front "cheek" armor, that was only 100 mm thick. However, the "flat" portion of the "cheek" is quite small (a few inches?) and the effective armor seems to have been considerably greater than 100 mm, based on the recommendations of TsNII48's review of the IS-1/IS-122 armor profile in early 1944.

    TsNII48's review stated that to raise the armor protection of the IS-1/IS-122 hull (based on the KV-13) to make it proof against hits from the Panther's 75L70 gun, one would need to raise the 120 mm thickness on the upper hull to 145-150 mm, and increase the base turret armor to 130 mm. The increase in thickness recommended for the upper hull (120 mm sloped at 30 degrees, which calculates to US Army metric to an effective thickness of 150 mm, given the US Army multiplier of 1.25) would increase the effective upper hull thickness to almost 190 mm. This effective thickness niches precisely the point-blank penetration of the Panther's 75/L70. of 185 mm at 100 meters (again, using Western metrics), and therefore would indeed provide protection.

    Ergo, I would conclude that TsNII48's recommended increase to 130 mm on the IS turret would likewise provide an effective thickness of almost 190 mm, resulting in a multiplier of about 1.45. This means the effective thickness of that 100 mm of cheek armor was about 145 mm. A relative weak point, to be sure, but not absurdly weak, as some commentators conclude. The IS-1/IS-2's weak point was the lower frontal plate, which was a relatively low-probability target.

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    1. It failed to search for that video:/
      But anyway the turret mask or cheeks have some flat areas outside but inside its reduced by curveing armour thicknes. So if the projectile hit 100 mm left from the mantled where the armour is still quite flat it will definitely burrow to the left side part of cheek instead of fly to the inside even with Pak 43.
      As I cant see turret mantled from the side or back are you abble to confirm that the area of 200 mm thickness is wider than its own thickness?
      Upper hull front can resist to any german anti tank gun even at short distance but there is probably one problem. If the projectile from Pak 43 will hit higher part of that armour it will beounce to the lowest part of the mantled where is just 60 mm thickness.

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    2. Crabteeth--look at the photo of this IS-2 I linked (here it is again):

      http://i211.photobucket.com/albums/bb262/netnguy01/JSU-122/JS-2%20big%20captured_zpstlkhwrgj.jpg

      Here is the tank review video again, hope it loads for you.

      https://www.youtube.com/watch?v=f1_qvmVhMrA

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    3. Good day !, I ask you to share a link to the following: 1) the instruction of German tactical anti-tank IS-2 2) the results of testing the Germans IS-2 model 1943. on Russian resources is nothing like there is no hope for help.

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  3. The center over-mantlet is pretty narrow and would have an edge-effect multiplier of about 0.75. Plus it is cast armor and would have an additional multiplier of 0.9-0.95.

    As to having 200mm of armor on the center cheeks seems debateable.
    http://www.williammaloney.com/Aviation/MilitaryMuseumOfSouthernNewEngland/JSJosephStalinTankMainGun/pages/04StalinTankRecoilNMantlet.htm

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    1. The review I cited from War Thunder displays the armor layout pretty well, including overlap regions (I did not know, for example, that the two 90 mm side plates also overlapped). I would not call the overlap of the mantlet armor over the turret face particularly "narrow" myself.

      As for the resistance of the non-mantlet front "cheeks", another argument for something like 145 mm of effective armor comes from a surprising source: German testing, of an IS-2 mod 1943 (not 1944) with wider "cheeks" than the later mod 1944. German testing concluded that the Panther's 75L/70 could only penetrate the non-mantlet front "cheeks" at 800 m or closer (tables of the 75/L70 have it penetrating 149 mm of armor to 1000 m). So if anything, by that metric an estimate of 145 mm of effective armor is conservative.

      As for picture of tank #441 of the 7th Guards tank brigade, I couldn't find it online so I uploaded a picture of it. As I said, when I used published dimensions of the IS-2 I measured 110 mm on the edge of the mantlet in the foreground, but as you can clearly see it's much thicker (> 200 mm) near the gun. And no, that does not include a measurement error due to the gun's bracket, as that has been blown well down the gun tube.

      http://i211.photobucket.com/albums/bb262/netnguy01/JSU-122/JS-2%20big%20captured_zpstlkhwrgj.jpg

      Oh, and the people who designed the game War Thunder have access to a real, working, IS-2 (it even shoots!). In their game there is more detail about the armor than I've ever seen anywhere else. That to me adds to their credibility.

      https://www.youtube.com/watch?v=hxfyvzslLLg

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    2. “I measured 110 mm on the edge of the mantlet in the foreground, but as you can clearly see it's much thicker (> 200 mm) near the gun. And no, that does not include a measurement error due to the gun's bracket, as that has been blown well down the gun tube.”

      Are you are talking about that narrow sleeve? It poses little defense as its only about 50mm thick near the barrel opening. The Germans measured the mantlet as 70mm at the top and lower edges and 110mm at the center. The mantlet behind the bracket/sleeve that was blown down the barrel is flat not curved so it isn’t the full 110mm thick.

      One enthusiast climbed on the one at Czech museum at Lesany. The result was: large (wide) mantlet with the 120mm on the one side and 80mm on the second side. (I don‘t know how they measured it though.)

      The one in the US will be available to the public when the water damage is repaired at the museum. A better solution is for someone on the US East coast to make a pilgrimage to it and take an ultrasonic measuring device with them. Some cost as little as $300. The one I have can measure up to 200mm.

      Not that I don’t trust War Thunder nor you to get it right, but I don’t.

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    3. a) That "narrow sleeve" according to War Thunder is sufficient to cover the opening for the gun to stick through; the area not covered by turret armor. That's quite wide enough.

      b) As for the mantlet figures you cite from German sources (i.e., the 70 mm thickness at the top), those are *NOT* for a IS-2 mod 1944, but for the IS-1/IS-2 mod 1943 and are thus not relevant (I have the picture of that captured vehicle too, if you want to see it). Insofar as I know the Germans never were able to obtain a IS-2 mod 1944 sample to evaluate.

      c) I'm aware of the measurement done at the Czech museum (80 mm on the large edge, 120 mm on the narrow; I follow this blog and these threads). The guy doing the measurement used metal measuring tape (I recall seeing the picture) stuck into the cracks at the mantlet edges. He also stated that there was armor *behind* at least the wide part of the mantlet, which agrees pretty much with what the War Thunder presentation says.

      That's why I wrote "180-220" mm on the overlapping thickness, because I was aware the wider edge thinned out to 80 mm.

      Finally, d) I guess I don't expect you to trust me, and maybe not the War Thunder creators either...though the review I posted I think goes beyond Baryatinskiy's book (which I also have) in making sense of this tank.

      But I don't see why it's so hard to disbelieve that this tank had the overlapped frontal armor of the thickness described. That not only fits with its in-combat resistance and survivability (as described above), it also is perfectly consistent with similar tanks of the period and weight class. The M26 Pershing, too, had "only" 102 mm of mantlet armor but that too overlapped turret armor, same deal. There is a War Thunder review of the M26 describing its armor layout just like the IS-2 mod 1944:

      https://www.youtube.com/watch?v=odBSlgLfLwM

      In fact, the common knock against Soviet heavy tanks is that they're a) cramped, b) have limited ammo storage, and c) limited gun depression. That may be true (though the IS-2's ergonomics were actually pretty good) but these are a consequence of making a tank "small for its size, with smaller dimensions and limited internal volume. But the upside of building a tank this way is that you can build a tank with *thicker* armor using small dimensions can you can have on a tank of bigger dimensions given identical same weight constraints.

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    4. I missed the later posts of this old thead.
      http://tankarchives.blogspot.com/2013/11/improving-is-2.html

      Amizaur apparently did measure this with an ultra-sonic and we are all wrong to a degree. The wide mantlet is 120mm near the gun (over the opening for the gun) but thins out to 80mm near the gun sight and edge. So with a 80mm turret under the mantlet giving a combined front turret of 160mm in front of the gunner. The front turret cheeks are 100mm. The Czechs measured the mantlet not the cheeks.

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    5. Here are two images that show the front of the turret but they seem to be at odds with each other what they show.
      http://img706.imageshack.us/img706/1984/turretblue.jpg
      http://img85.imageshack.us/img85/8866/0574c8b5100ed7xl.jpg

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    6. Found it! The smoking gun. Take a look at the 100mm thick armor behind the mantlet. Ooops, these kids must of stole it.
      http://worldwartwozone.com/gallery.old/500/medium/schulaufsaetze.jpg
      -M

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    7. Found it! The smoking gun. Take a look at the 100mm thick armor behind the mantlet.

      Thank you, M. I was aware of Amizur's measurements earlier, but thank you of the work digging up the old thread. I too did not know he went back and did more measurements with an ultrasound device (would these devices measure the thickness of spaced armor, or only that of the top plate?)

      And your last picture was precisely the perspective needed to resolve this. There are several images of an IS-2 where the front part of the turret is blown off, but the mantlet remained. I posted a picture of the mantlet blown down from the side, but that does not show the turret armor. Your photo does.

      Though come to think of it, I think one of Zaloga's books also shows another frontal perspective of a "hybrid" mod 1943/1944 IS-2 (an IS-2 with the mod 1944 wider gun mantlet, but still with the KV-13 hull) where the mantlet was blown off by an internal explosion. I'll see if I can dig that up at home.

      Once more, thanks.

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    8. "would these devices measure the thickness of spaced armor, or only that of the top plate."
      Only the plate you can place it on. You would have to measure inside and out, like Amizaur did, to get both plates.
      -M

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    9. Only the plate you can place it on. You would have to measure inside and out, like Amizaur did, to get both plates.

      I fdigured that would be the case, given that paint flakes i interfered. Though I would think that measuring the inside thickness would be a chore, given the gun breech, sights, and other "stuff" getting in the way.

      Oh, and I mis-remembered; I found the Zaloga picture of the IS-2 I referenced, but it was yet another picture of an IS-2 (unambiguously a mod 1943, alas doubly) with the front turret casting blown off and with the mantlet still attached to the turret face. I've seen several pictures of that; it seems when I IS-2 blew up the turret front casting tended to separate from the rest of the turret before the mantlet separated from the turret face.

      Either that's a result of where the ammo that blew up was stashed, or they really bolted that mantlet down to the turret face securely (probably the former, as you'd think you might have to remove the mantlet to replace or service the gun; I don't know).

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    10. Speaking of Zaloga, now I know how he comes up with the 160mm of front turret armor for the JSII in his WWII Soviet tank book. 80mm + 80mm for the area near the sight.

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    11. Speaking of Zaloga, now I know how he comes up with the 160mm of front turret armor for the JSII in his WWII Soviet tank book. 80mm + 80mm for the area near the sight.

      And probably (conservatively speaking) that 80 + 80 mm area extends from the edge of the mantlet near the sight, across that face towards the gun.

      I still believe the photo I posted, though, that near the gun tube it starts increasing in thickness to over 200 mm right at the gun I believe that Amizaur couldn't accurately measure this very thick area, possibly due to the obstructions from the gun breach (inside the tank) and the mounting brackets (outside the tank). Or maybe it could be a limitation of his measuring device. But the War Thunder review mentions it and I now am more confident of my photo measurement it exists.

      Going from the gun to the the left edge fo the mantlet (facing the tank) the mantlet decreases to about 110 mm. Llkely at that point, it too overlays turret armor--if not 100 mm, then 80 mm, like on the sight side, giving a combined thickness of at least 190 mm.

      So--if you're facing an IS-2 mod 1944 in a Panther, where do you shoot? If you shoot right for the gun itself, your shot could be rebuffed by the 200 mm plus mantlet armor near the gun. Shoot to the right of the gun, at the mantlet, and you hit 110 + 80 mm armor, not good. Above either plate. the armor may be thinner but the slope likely to cause a ricochet.

      You could try to hit the non-mantlet front "cheek" armor, where it's a curved 100 mm, and if you manage that, you're good--by German testing out to 800 mm, maybe out past 1000 mm. But then you're trying to hit small areas-- the size of large postcard--which is not good. Miss by a little to the top, bottom, or outside your shot deflects.

      So...you shoot at the mantlet to the left of the turret, where it's 80 + 80 mm. That has some curvature (25 degrees) but it's the best target considering a combination of armor thickness, slope, and ease to-hit. As a bonus, you''ll likely to cripple or destroy the tank on a penetration by killing the gunner and maybe detonating the ammo.

      And, guess what? By this calculator:

      http://www.wwiiequipment.com/pencalc/

      Taking the Panther's 75/L70 gun, using its APCBC round, shooting at an IS-2m turret, going to "Advanced Options" and plugging in 80 mm of high-hardness cast armor for both the initial and second plate, you get a a vulnerability cone where the Panther's round is likely to penetrate the IS-2 out to a little more than 600 m. Just like it was recommended to Panther crews in German tactical instructions.

      Like i said, this information seems to make sense of what had been a maze of conflicting and confusing data.

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    12. Shoot to the right of the gun, at the mantlet, and you hit 110 + 80 mm armor, not good.

      Oops, that should read "left of the gun", not right, at least from the perspective of someone facing an IS-2 mod 1944. My bad.

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    13. I'm not convinced that there is that much protection accorded by the front roto-shield (mantlet) to the right (facing tank). Let's look at a penetration there. http://img85.imageshack.us/img85/8866/0574c8b5100ed7xl.jpg
      We can see there is about 1-1.5" of sleeve around the barrel. That's about all that's left of the “200mm armor” around the barrel. This is like the sleeves around many other tanks barrels. To keep a hit near there from going through the barrel. To the right of this it’s only 100mm-80mm
      The 160mm of armor of the mantlet near the right cheek is weaker than 160mm for two reasons.
      1. There is a slot opening in the middle for a sight to move up and down.
      2. According to Lorrin Bird's World War II Ballistics: Armor and Gunnery - armor-wise two 80mm plates are not as good as a single 160mm plate. The second of two equal homogeneous plates is only worth ~77% of its thickness. So the total would be equivalent to 142mm even with no opening

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    14. Let's look at a penetration there. http://img85.imageshack.us/img85/8866/0574c8b5100ed7xl.jpg

      First, I would contend that's yet another picture of whole the front turret casting removed from the tank, not the mantlet itself. Nor do I know what angle that round penetrated...or if it's even a penetration at all, but a hole created by the internal explosion. The fact that 122 mm gun itself seems to have been blow apart to me argues that it's the explosion result.

      We can see there is about 1-1.5" of sleeve around the barrel. That's about all that's left of the “200mm armor” around the barrel. This is like the sleeves around many other tanks barrels.

      Quite frankly, I think my picture is a better view. I mean, if you want to measure the properties of a mantlet from a photo, wouldn't a photo that showed the mantlet isolated from the rest of the tank be better than one where the mantlet is largely obscured by other things? I think mine shows the more unambiguous perspective, from the side (which is the best way to try to measure its thickness), and not one largely obscured from the front. My picture does not show a "sleeve" as much as a more gradual thickening of the mantlet around the gun (maybe at like a 30 degree angle from end to mantlet?).

      The Tiger II, for instance, has such a "sleeve" you speak of--in fact it protrudes out through the mantlet!--but the picture I posted shows something different. True, it's only over 200 mm at the end, but it takes about the length of the man's hand in the photo to go gradually down from over 200 mm to to base mantlet thickness. That's not a "sleeve".

      1. There is a slot opening in the middle for a sight to move up and down.

      True enough, especially for one very unlucky gunner speaking of the tank at the New England Military Museum. Any tank suffers similar weak points; no matter how great your armor, there's always that lucky shot that can do you in.

      2. According to Lorrin Bird's World War II Ballistics: Armor and Gunnery - armor-wise two 80mm plates are not as good as a single 160mm plate. The second of two equal homogeneous plates is only worth ~77% of its thickness. So the total would be equivalent to 142mm even with no opening

      I would have though that calculus to be included in the WWII equipment site I linked to. It gives you the option of armor grades and layered options. I calculated a cone of 600 m vulnerability for the right mantlet side of the IS-2 mod 1944 to the Panther's 75/L70 APCBC round, using "cast, high-hardness" option for armor type and 80 mm for both plates designating that the plates were "spaced" (as opposed to a "layered" option). I did not simply plug in "160".

      While I don't necessarily take such calculated results from this site nor any other as the gospel truth, I do note that in this case it niches very well with German tactical instructions to Panther crews.

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    15. ". I calculated a cone of 600 m vulnerability for the right mantlet side of the IS-2 mod 1944 to the Panther's 75/L70 APCBC round, using "cast, high-hardness" option for armor type and 80 mm for both plates designating that the plates were "spaced"."
      My program that plots out the normalized average of all 75/L70 data puts the penetration (per US V50 criteria) at 600m as 141mm.
      So...OK
      -M

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  4. More
    http://www.usmilitarymuseum.org/Exhibits/Exhibit_21.pdf
    EXHIBIT # 21
    JOSEF STALIN 2 TANK GUN USSR
    The Josef Stalin 2 was the heaviest Russian tank to fight in WWII. It featured a giant 122 mm high velocity gun which used two part ammunition that made reloading time consuming. In May 1945, this Josef Stalin tank was destroyed by a German 75 mm shell. In normal circumstances the shell would have been deflected by the Stalin 2’s heavy armor. But in this case, the German scored a lucky hit on the gunner’s optical sight. The round penetrated the
    armor killing the gunner instantly and then deflecting off the interior armor until it struck the ammunition storage. The resulting explosion sent this piece of the Stalin 2 flying through the air. The artifact was recovered by the United States Army shortly after the war and was secretly sent to the Aberdeen Proving Grounds in Maryland for intelligence purposes.
    -M

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    1. I was aware of this display; I've seen it before. However any hit on an opening on any tank is a potential penetration. I have posted the photo above of the detached mantlet on an IS-2, you are free to do your own measurement.

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  5. Please check: http://forum.warthunder.com/index.php?/topic/288445-is-2-front-turret-and-gun-mantlet-armor-measured/

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