rexford

This is from Vasiliy Fofanov's posts on Yahoo!Tankers site: "Considering that the war diaries of advancing Germans had as early as June notes that Soviet 45mm guns were just as useless against their panzers as their own 'door-knockers' against T-34 (see e.g. Glantz "The initial period of war on the Eastern Front")" Vasiliy was forwarding the idea that Russian 45mm ammo was questionable during June 1941 and did not suffer any major decrease.

Valera Potapov noted in the past that 45mm ammunition suffered from quality problems during late 1941 and early 1942, leading to decreased penetration. Here are some penetration figures from German and Russian sources that show the extent of the problem. Data is for 45mm L46 gun firing APBC of some sort. Numbers in brackets are 0 degree estimates from 30 degree figures, using slope effects for APBC. Armor is homogeneous. 45mm APBC 1940 Russian Penetration Tests, 0 Degree Impact 55mm at 300m 45mm at 600m 40mm at 1000m 30mm at 1500m This would be pre-war, and the numbers are fairly close to what we predict for 45mm APBC. 1942 German Tests at 30 Degrees 40mm at 100m (46mm at 0 degrees) 28mm at 500m (31mm at 0 degrees) 19mm at 1000m (20mm at 0 degrees) Vasiliy Fofanov has posted, on Yahoo!Tankers site, that 45mm gun had trouble penetrating front and side armor of panzers beyond 500m during 1941. He stated that one of David Glantz' books includes material on the inability of 45mm anti-tank guns to defeat panzers during June 1941. The 1942 German tests show a great drop in penetration from 1940 tests. The problem was so bad, according to Fofanov's recounting of the passage, that the panzer crews referred to the 45mm ATG as the Russian equivalent of the German 37mm door knocker. I will try to find the book by Glantz that is supposed to include the above passage. German Data in Panzertruppen 1943-1945 30 degree penetration by 45mm APBC 42mm at 100m (48mm at 0 degrees) 35mm at 500m (40mm at 0 degrees) 28mm at 1000m (31mm at 0 degrees) 23mm at 1500m (25mm at 0 degrees) My estimates at 0 Degrees 64mm at 100m 58mm at 250m 49mm at 500m 43mm at 750m 38mm at 1000m 32mm at 1500m The 1940 Russian tests result in figures that are close to my estimates. Panzertruppen and 1942 German figures show decline in penetration performance. 1940 and 1942 test data from Miles Krogfus.

Jeff Duquette stated: "The adoption of the D-25T to the IS-2 appears to have been ultimately a case of simple wartime expedience. Ammunition and the facilities to produce ammunition were readily available for the A-19/D-25T." The discussion of whether the 122mm or 100mm should be on the IS-2, which is presented on Russian Battlefield, appears to have taken place during August 1944, well after IS-2 with 122mm was in production and use. The discussion appears to be centered on whether the 100mm gun would be a better choice for future IS-2 tanks. The factors presented weigh against the 100mm gun. The ammo availability factor was to later delay introduction of SU 100, based on Russian Battlefield articles, when 100mm APBC could not be produced in satisfactory manner. The letters presented on Russian Battlefield appear to be based on experience with 100mm pre-production prototype. Ammo availability does not appear to be discussed in the three letters as a major factor.

In response to an earlier post on this thread regarding differences in penetration ranges for 122mm ammo against Panther glacis, here is an explanation: 122mm APBC has a flat nose and superior performance against sloped armor, since ricochet causing forces are decreased with a flat nose. U.S. firing test data for 122mm APBC at angles from 0 through 70 degrees predicts 1800m+ penetration range against 80mm @ 55 degrees Panther glacis. 11/43, 122mm goes thru glacis and out hull rear at 1500m, which suggests penetration range above 1500m 9/44, 122mm goes thru glacis at 2500m with energy to spare, we interpret this result as due to flawed or brittle armor which decreased penetration resistance Zaloga indicates 1000m or less range to effectively fight Panthers, well, hitting beyond that range may have been a problem which would be magnified due to 9 or 10 rounds of armor piercing ammo (can't afford to sit back at 2000m and fire away hoping for a hit). One important factor is the time frame that the Zaloga quote comes, since early IS-2 crews might have alot more trouble hitting beyond 1000m than late 1945 crews which fought duels with Tiger tanks at 2500m and beyond. Russian Battlefield states that APBC could penetrate Panther at 1000m and 1200m, well, maybe accuracy, ammo limits, terrain and other factors limited hits to those ranges. Regarding Russian AP, Russian Battlefield gives it a 600 to 700 meter penetration range against Panther glacis till summer of 1944, when armor appears to lose resistance and effective range increases. If the IS-2 tanks that Zaloga's quote applies to were carrying mostly AP, then the effective range to fight Panthers frontally would be 1000m at some point. Lorrin

In response to the 122mm goes in and out Panther (in glacis and out the rear hull), a post on the Tankers site noted that a Sherman vet made a scale model diorama where a Sherman was sitting with a hole in the glacis and the engine sitting well beyond the back of the tank. Turns out the diorama was not depicting maintenance, the situation was directly after a 75mm or 88mm German round penetrated the glacis and drove the engine off the mountings and out the tank rear. The post concluded that strange and unusual things do occur, like a 37mm armed armored car knocking out a Panther on a frontal shot (actually happened). Lorrin

As I noted to Jeff on the Tankers site, the ranges quoted by Zaloga for Panther vs IS-2 combat appear to take into account accuracy as well as penetration. Zaloga's quotes do not state ranges were limits of expected penetration, they state that those were the ranges for effective combat (which I interpret as hit and kill combination). Russian Battlefield includes statement that IS-2 crews would be hard pressed to hit beyond 1000m unless very well trained and experienced. During first months of IS-2 use few crews would qualify as experienced. Does Zaloga indicate what period of the war his quoted penetration ranges refer to. With regard to the use of U.S. 122mm APBC firing tests to predict penetration of WW II IS-2 against Panther front, Jeff ignores the many excellent predictions that we have made using the U.S. test data. 100mm APBC against Panther glacis is predicted to within 100m or so in our book (which Jeff has). A post that analyzed Russian firing test data for 85mm APBC against Pershing armor is on Tankers site where penetration ranges against 101mm cast at 43 degrees, and other areas. is very closely predicted when compared to Russian test findings. For 100mm and 85mm APBC we predicted results from 122mm APBC firing test data from U.S., modified for slope effect and impact velocity. The number of test firing results that support use of U.S. firing test data for 122mm APBC, and predictions for other Russian APBC from that data, continues to increase each month. Instead of being hard pressed to find reports and tests to support our findings and predictions, the data base is increasing at a steady rate. Regarding that 11/43 test of 122mm against Panther glacis, Miles Krogfus has the original test report and it states the following: Tank was knocked out during July 1943 by a 76.2mm side hit. Was brought to Moscow for show, insides were stripped out and the tank was subjected to firing tests (engine is removed at this point along with other internal mechanisms in hull and turret). 122mm hit on glacis goes through and then exits through 40mm rear hull plate. The story about a 122mm round penetrating the turret side and going out the other side may have also occurred during 11/43 tests, but Miles is concentrating on the glacis/hull rear report aspects. Claus Bonnesen used the serial number for the Kubinka tank that Miles presented on Tankers site to identify the Panther tank number. Picture of that tank on Russian Battlefield site show it to be in good condition after Russian capture, prior to Kubinka tests. U.S. firing test data with 122mm APBC predicts 1800m+ penetration of 80mm at 55 degrees, 11/43 test shows penetration range is way more than 1500m if round defeats glacis and rear hull. Russian firing test at Kubinka during 9/44 shows 122mm penetrating Panther glacis at 2500m. Lorrin

If one goes to the following page on Russian Battlefield, and reads the three correspondence letter on IS tank use of 100mm gun, they will see interesting reasons why 100mm gun not chosen for IS tanks: http://www.battlefield.ru/library/archives/index.html 100mm gun outpenetrated 122mm at normal combat ranges but came with many drawbacks, including longer rounds to load into gun, increased fumes in turret, insignificant increase in ammo storage, etc. See letter 3. More than penetration went into decision to stick with 122mm, which may have also considered HE capability. 122mm HE projectile is 15.2% HE filler by weight, 100mm HE is 9.3%, based on figures contained on Russian Battlefield. Also interesting is discussion of ability of 122mm gun to fight German tanks, in particular (letter is written 1944): "At the moment, "JS" tanks armed with the 122 mm main gun are successfully repelling all counterattacks by German tanks of all types at all ranges (i.e. up to 1500 metres);" IS tanks were expected to defeat German tanks, and were doing it. U.S. firing tests with 122mm APBC predict that 122mm APBC will defeat excellent quality Panther glacis at 1450m against 85mm plate thickness, and 1850m against 80mm plate thickness. [ February 09, 2002, 07:13 AM: Message edited by: rexford ]

The following two interesting pieces of information were found on the Russian Battlefield site: http://history.vif2.ru/atwar/tankers/loza/loza1.html Interview with Mr. Loza: "I want also to add that the Sherman's armor was tough. There were cases on our T-34 when a round struck and did not penetrate. But the crew was wounded because pieces of armor flew off the inside wall and struck the crewmen in the hands and eyes. This never happened on the Sherman." T34 had very high hardness armor with brittle tendencies, Sherman after 10/43 had ductile armor with little tendency to shed fragments. In other paragraphs Mr. Loza comments on the accurate German tank sights as well as a host of other issues. ------------------------------------------------ http://history.vif2.ru/atwar/artillerymen/monyushko/comments.htm Interview with Mr. Monyushko: "What strengths and weaknesses of German guns can you point out? - When combat qualities are concerned, the 88mm guns installed on Tigers and Ferdinands were very accurate. Although, I don't know if that was connected with the gun itself or the sight, since their optics were excellent. But their field artillery was too complicated. There were very many various devices on a gun. This seemed like a shortcoming to me. It also couldn't be transported conveniently: all our guns had tires made of elastic resin. A gun wasn't as shaken during transportation, and its mechanisms were not upset. But Germans had either metal wheels, or those made of tight resin that absorbed shock badly. You had to recheck all sights after it got jolted during movements. Plus, their guns were heavier. As to the strengths, I would note excellent sights with illumination. The design of their guns even included a place for an accumulator. But it was difficult to work with ours in the darkness." Little differences that could make a large difference. One of the interesting statements in the Russian Battlefield site Artillerymen interviews was a comment that the Russians gladly traded guns for tanks. 45mm and 76.2mm towed guns could usually knock out a few tanks before they would be lost to tank gun fire, machine guns or mortars/artillery, which was considered to be a good exchange.

The following site for PST and other 1/72 scale models has some neat plastic and resin kits on German conversions of KV tanks: http://home.att.net/~d.kuligowski/ Go to World War II then go to PST then go to PST web site at bottom of page Enter the site by clicking on the Welcome statement under the converted KV tank and go down the list to see the kits for KV tanks in German use. The list provides pictures of the kit boxes. Lorrin [ 01-27-2002: Message edited by: rexford ] [ 01-27-2002: Message edited by: rexford ] [ 01-27-2002: Message edited by: rexford ] [ 01-27-2002: Message edited by: rexford ]</p>

The following site for PST and other 1/72 scale models has some neat plastic and resin kits on German conversions of KV tanks: http://home.att.net/~d.kuligowski/ Go to World War II then go to PST then go to PST web site at bottom of page Enter the site by clicking on the Welcome statement under the converted KV tank and go down the list to see the kits for KV tanks in German use. The list provides pictures of the kit boxes. Lorrin [ 01-27-2002: Message edited by: rexford ] [ 01-27-2002: Message edited by: rexford ] [ 01-27-2002: Message edited by: rexford ] [ 01-27-2002: Message edited by: rexford ]</p>

We are developing face-hardened penetration figures for Russian APBC, and need combat data. The SU 152 at Kursk obtained the nickname "Zvierboy", or animal hunter, according to Advanced Squad Leader rulebook due to effectiveness against Panthers, Tigers and Elefants. Did the SU 152 at Kursk defeat the Panther glacis or nose armor (front hull), and is data available on effective ranges against that armor. Our current penetration data estimates and slope effect multipliers allow SU 152 to defeat face-hardened Panther D glacis at 1800m. Thank you for assistance.

T34 armor is high hardness (beyond ability of normal machine tools to cut), and relatively thin compared to projectile diameter, so will lose about 25% of its resistance against 75mm German projectiles. The indicated penetration ranges for 75L43 in Thomas Jentz' books, 1200m on any angle hit and 1600m maximum, match up well with armor resistance estimates using high hardness modifiers and a slight to non-existent quality decrease from there. What was really variable about T34 armor may have been the thickness, German firing tests against T34 like armor use 40mm to 50mm design thicknesses, and measurements of 45mm design thickness on SU 100 and other tanks range from 42mm to 50mm. When armor plate is brittle and projectile diameter is much larger than thickness, variations in plate quality have a much smaller impact than thickness changes.

In response to Jason C, firing tests show that a 32mm face-hardened plate covering a 30mm face-hardened plate resists like a 69mm face-hardened plate. This isn't an equation result, and it was 32mm over 30mm. With face-hardened armor the very hard and thin surface layer provides most of the resistance, and there are TWO face-hardened layers that need defeating on the PzKpfw IIIH hull front. With homogeneous armor, the surface layers are weaker, so 32mm over 30mm is much less than 60mm. Firing tests against PzKpfw IIIH show that 32mm/30mm (both face-hard) resists like 69mm face-hard. When 32mm is bolted over 30mm, angled hits tend to bend the studs holding the plates and create a maintenance headache. Easier for Germans to use a single 50mm plate, which also weights less and allows PzKpfw III to maintain excellent mobility. Germans could weld 32mm face-hard over 30mm face-hard, but high hardness armor does not weld very well. Lee: Charles and company have a copy of our book where we discuss the PzKpfw IIIH layered face-hardened armor (32mm/30mm) which resists like 69mm face-hard. One question that Jason brings up is how many PzKpfw IIIH fought on the Eastern Front. It sometimes sounds like most were in Nord Afrika. The stories that Jentz provides give T34 tanks a 1200m to 1600m stand-off range against PzKpfw III and IV, where the 76.2mm rounds will easily penetrate German frontal armor. The 76.2mm will penetrate 50mm face-hardened frontal armor at about 1600m without much trouble, and easily defeats 30mm frontal armor. The 32mm/30mm layered face-hard armor might not be penetrated beyond 1000m by a T34, but a few large caliber hits from 76.2mm might damage the studs. The PzKpfw IIIH turret front is extremely vulnerable to 76.2mm hits at any range. The Germans manufactured: 435 PzKpfw IIIF 550 IIIG 308 IIIH 1,549 early IIIJ with 50mm L42 1,067 IIIJ with 50mm L60 903 IIIL and IIIM Note that IIIH is smallest group from factories, although quite a lot of the IIIF and IIIG were converted to IIIH via added armor on front. The Jentz stories about T34 vs PzKpfw III and IV are mid-1942, which is when IIIJ were being mass produced. It is interesting that Jentz does not talk about the panzer units moving IIIH models to the head of the groups due to better armor. Maybe the two or three situations described in Jentz regarding how T34 ripped up panzers related to IIIG and IIIJ tanks (with few, or no, IIIH). There just isn't enough information to say that a T34 could or couldn't penetrate the front hull of a PzKpfw IIIH beyond 1000m. I can't recall ever seeing a picture of a PzKpfw IIIH on the Eastern Front, although they must have been there. If PzKpfw IIIH was on the Ostfront, they would be a small percentage of the mid-1942 tanks.

Jeff, The Russian Battlefield article is not the keystone to any argument, it is a piece that helps to put many other materials in perspective. The Americans in Europe did tests during August 1944 that showed previously undamaged Panther plate to be brittle and crack in two of three cases after a few non-penetrating hits. Firing tests conducted at Aberdeen Proving Grounds (3) and Shoeburyness (1) after August 1944 also show a tendency of some undamaged Panther glacis to crack on non-penetrating hits. The date of Panther manufacture in those cases is also consistent with the Russian reports. The Russian reports suggest that summer 1944 is when the brittle results started to become noticeable. So Panthers in Russia and Italy prior to summer 1944 probably carried excellent armor to resist 122mm hits so well during the cold winter and early spring of 1944. The Russian reports are being translated into English by non-metallurgists. Armor is heat treated to a higher hardness, which might have been translated as tempered. The explanation about alloy shortages leading to Panther glacis problems seems to make sense but may not be strictly correct. Things like that happen during translations by non-metallurgists. But when the Russian Battlefield reports state that 122mm AP performance improved dramatically during summer of 1944, that is a direct statement. The Russians connect the AP effectiveness change to Panther glacis problems related to alloy availability, which is consistent with many other materials and tests. Lorrin

Jeff, I answered Vasiliy's post on Yahoo!Tankers site. Didn't you read my response? The Russian Battlefield site clearly differentiates between performance of 122mm AP and APBC (have you read the section?). For combat with Panther prior to summer 1944, Russian Battlefield says 122mm AP only penetrates glacis to 700m and mostly ricochets at all ranges. 122mm APBC penetrates to 1200m, so site indicates that AP and APBC available at same time and discusses each separately. Russians started to look into ammo improvements due to poor performance of 122mm AP and then during summer 1944 AP effectiveness increased, so problem starts to disappear or at least become less critical before improvements found and implemented. This is how I responded to Vasiliy's post. I suspect that 122mm AP and APBC were both being made in about equal quantities due to the Russian worry about 122mm AP ineffectiveness (AP is cheaper than APBC and equally effective against Pz IV and StuG III, which make up a good percentage of IS tank opponents). If you read the Russian Battlefield discussion you'll see that Russians weren't even aware of superior performance of 122mm APBC against thick sloped armor prior to first few months of IS-2 vs Panther combat. Then the Russians went to the designers and conducted firing tests to explain why APBC penetrated at greater ranges than AP. There was no movement to replace 122mm AP with APBC due to sloped armor penetration differences prior to summer 1944 because the Russians were not aware of the differences. If you read the discussion on Valera's site most of your comments would be answered. IS-2 was clearly expected to deal with Panthers and Tigers. I never discussed why 100mm gun was not chosen for IS-2, and do not intend to. I spoke on why 85mm gun in various Russian AFV was not sufficient to fight Panthers and Tigers, which made 122mm gun in IS-2 a big need.

The Russians spent alot of time and effort deciding which gun goes in the IS-1 and IS-2. The IS-1 with its 85mm was a failure, and the Russians noted that the 122mm gun was the most effective weapon at Kursk against Tigers and Panthers. The 122mm gun was chosen for the IS-2 after firing tests against captured Panthers, and the Russians were quite upset during the Panther-vs-IS-2 combats when 122mm AP always bounced off the glacis beyond 700 meters, and usually ricocheted at all ranges. The Russians were looking into improvements to the 122mm AP ammo when 122mm AP started to improve against Panther glacis during the summer of 1944 (due to more brittle glacis armor as a result of alloy rationing, according to Russian speculation on the subject). The performance of 122mm AP against the Panther front was a major problem for the Russians for many months, which suggests that IS-2 tanks were expected to take on Panthers and defeat them with armor piercing rounds. If 1/3 of the 122mm ammo load is AP or APBC, that's about 10 rounds. At 1.5 rounds per minute that equates to 6 or 7 minutes of continuous AP/APBC fire. How many minutes of continuous APCBC fire can a Panther do? Say 6 rounds per minute for 7 minutes, 42 shots. That sounds like the Panther APCBC ammo load could be shot off in the same time frame that an IS-2 takes to shoot all the AP/APBC. An SU 85 actually carries more HE than AP/APBC, we have seen the Russian figures. Most Russian tanks carry more HE than AP/APBC, from what we've seen. SU 85, T34/85, KV 85 and IS-1 (85mm gun) were failures against Tiger and Panther, IS-2 was developed to take on Panthers and Tigers and blast the heck out of German bunkers and emplacements. 122mm HE was much more effective against structures than 85mm HE, where 85mm HE probably caused less fragmentation than 76.2mm HE. IS-2 was developed to fight German "cats" and blow up emplacements and structures. Slow rate of fire and limited ammo load are the trade-off. But a limited ammo load is not as much of a problem as it would seem if the rate of fire is very low. CMBB should keep the IS-2 ammo load and proportions historically correct, but IS-2 did fight German tanks and when the IS-2 did not do well in the first several months of fighting Panther the Russians were worried. That is one of the reasons why the IS-2 front hull armor was greatly improved, due to the heavy losses that IS-2 tanks suffered. A 75mm Pak did not kill IS-2 tanks frontally, Tigers, Panthers and Nashorn did.

Miles Krogfus recently sent me some very valuable information on German weld and armor quality, as well as firing test data against Panthers from Aberdeen Proving Grounds (3 tanks) and Shoeburyness England (1 tank). The firing tests were conducted against glacis armor which had not been previously hit, and the the tanks had not burned. Miles' information shows that German alloy use for welding was cut starting January 1944. The firing tests show that glacis armor on 3 of 4 Panther tanks (Ausf A and G), when under attack by rounds which should not penetrate (17 pdr AP and APCBC, 90mm APCBC), developed cracks, sprung welds and allowed some complete penetrations that should not have occurred. If the manufacture of Panther glacis armor and accompanying welds started to stand a statistical chance of lowered resistance during early 1944, this would include a good sized percentage of Panther A tanks. From a wargaming perspective, CMBB scenario's from about June 1944 could allow the German player to pick Panther tanks, but the knowledge of how many could have deficient glacis armor and welds would not be known. The percentage might increase with the months that follow June 1944, if that month is selected as the "start date". Otherwise players who suspect Russian use of 100mm, 122mm and 152mm guns might opt for Panther D and early Panther A. For Russian players, IS-2 tanks appear to have received and used AP or APBC in no particular set pattern, based on Russian Battlefield articles regarding IS-2 development and combat use. It could be a random selection whether the IS-2 fires AP or APBC, where APBC is much more effective against sloped armor. So players might face two random selections, Panther glacis quality and 122mm ammo use. A similar ammo use randomizer would apply to 85, 100mm and 152mm rounds, which could be either AP or APBC. And the degree of Panther glacis resistance decrease could also be random. I would also note, for the benefit of the CMBB design team, that the slope effects for AP rounds in the book, WW II BALLISTICS: Armor and Gunnery, have been revised after analysis of recently discovered firing test data for angles over 40 degrees. When 122mm AP hits 85mm glacis armor at 55 degrees, the slope multiplier should be about 2.08. This is much lower than previously thought, and closely matches the reported penetration range of 122mm AP against good quality Panther glacis armor. If someone from BTS will contact me directly I will e-mail them the new slope effect curves and the accompanying table as jpeg files. This information will also be e-mailed to others who might like the new curves (and table). --------------------------------------------- Theories have been put forth by several persons on other sites that sprung welds may have been responsible for complete penetrations that should not have occurred against Panther glacis. That cracking a weld line would decrease the penetration resistance on follow-up hits. Opinions on this issue would be appreciated.

The following write up was presented on the Russian Battlefield in the FAQ section in response to a question as to whether T34 had 60mm hull front armor: "Here is my explanation. From December 1941, according to GBTU's order, the T-34s scheduled to be manufacture with 60-mm frontal armor, but Soviet industry was unable to do it. When it become clear, the Russians attempted to fit some T-34s with additional 15-20 mm armor plates, usually 15 mm. Also, these plated allowed to be made of common (non-armor) steel plates. Thus, 45 + 15 = 60 mm. The armor thickness of various turrets was different. Welded turrets usually had a 45-mm armor; cast turrets were of 48-52 mm armor, some latest turrets were of 56-58 mm armor." One of the key phrases is that the additional 15mm could be made of non-armor steel plates. The ballistic resistance of this thickness might be about half of the actual thickness. I think that some pictures of T34 with added 15mm note that scrap plate was used. It would be good if the above points could be verified.

The equation makes sense if one accepts that the thicker the plates the greater the proportion of thickness that would count as interior. So the effective thickness of two 40mm plates in contact and two 110mm plates in contact should be radically different. 40mm/40mm goes to 68mm using the naval rule of thumb, which is 68/80, or 85% of combined thickness. 110mm/110mm goes to 187 using naval guideline, which is 187/220, or 85% of combined thickness. Since thick plates offer more interior than thin plates (a 15mm plate is mostly surface material in terms of being penetrated), it would seem that a higher percentage of the total combined thickness would resist penetration with thick plates.

Regarding the comment about whether face-hardened armor works with the equations presented, I do not believe that it would. You're totally right, with face-hardened armor the surface is what does the damage, so more surface, more damage. Damn good point! Here is an explanation posted on another site after I read the above post on CM: A really good question has been asked about PzKpfw IIIH layered armor and the equations for plates in contact by Nikodemus on the Matrix Games forum. When the British fired at the 32mm/30mm layered armor on PzKpfw IIIH front hull, they used the 2 and 6 pdrs firing AP, the 37mm firing APCBC, and the Grant/Lee firing AP and APCBC. The resistance of the armor was the same against all rounds, anout 69mm face-hardened. Why would the two PzKpfw IIIH plates be better than a single 62mm plate, which is not predicted by the naval equation or the regression? Firing test results suggest that 32mm over 30mm, where both are face-hardened, resist like a single 69mm face-hardened plate. We think it is because the total thickness of face-hardened layers in the 32mm/30mm combo greatly exceeds the layer in a single 62mm plate, and it makes the projectile slam into two very damaging case hardened surfaces. With homogeneous armor the surface layers are weaker than the middle, so the more surface the less the resistance. Two plates together have much more surface than a single plate with same total thickness. But with face-hardened armor, the greater the face-hardened surfaces from two plates, the greater the resistance appears to be. The AP and APCBC rounds in the British test hit the face-hardened layer on the 32mm plate and are damaged but have enough momentum to drive through the softer backing. Then they hit the second face-hardened layer which probably inflicts ALOT more damage on the projectile nose. Usually with face-hardened armor, once the very hard surface layer is damaged the plate is open to defeat. But with layered armor once the first plate is defeated there is another hard surface staring at the round. The equations presented in previous posts are for homogeneous armor. Face-hardened armor is another story.

The following summary was e-mailed to me by Nathan Okun: "The Naval Technical Mission In Europe (NavTecMisEu) made several reports of Krupp armor and projectiles, including both Navy and Army materièl. In 1944, Krupp changed their specs for tank armor (naval armor was not longer being made) and made lower-alloy armor with reduced tolerances--Krupp never succeeded in making such armor resist as well as U.S. and British lower-alloy tank armors successfully developed during WWII." An attempt is being made to obtain the abovementioned report. Interesting coincidence that armor specs and tolerances are reported to change during 1944, the same year the Russians note a change in Panther glacis resistance to 122mm sharp nose AP. The British BIOS report, which analyzed the German armor industry during the war, came to the conclusion that German armor quality was maintained even when alloys were in short supply and quenching processes had to be radically changed, resulting in greater sensitivity to slight errors in time of quench.

In response to the posts on layered armor resistance to AP rounds when the plates are in contact, Nathan Okun e-mailed this writer regarding naval rule of thumb on the subject. Mr. Okun also noted that the equation he uses is consistent with the naval guideline. Naval rule of thumb is that when two plates are in contact, the equivalent single plate resistance equals about 70% of the thinner plate thickness plus the thicker plate. Mr. Okun has found that a "split the difference" approach works well, where the resistance of two plates in contact is taken as the average of the combined thickness and the resistance if the plates were spaced and did not directly interact. The equation he uses for single plate equivalence is: ((T1 + T2) + (T1^1.4 + T2^1.4)^(1/1.4))/2 The above equation will be referred to as the "working equation" in the comparisons at the end of this post. The results from the two abovementioned approaches were compared with the "three points" regression equation developed by this writer. When the maximum plate thickness is at least 2" and the minimum is 1" or greater, the three equations are fairly consistent in their predictions (less than a 10% variation between highest and lowest estimates). The following cases point out some of the larger variations between the three approaches: 1.5" over 1.5" (Sherman side hull with 38mm applique) Naval rule of thumb: 2.55" single plate equivalence working equation: 2.73" three points regression: 2.28" 1.0" over 1.5" (Sherman side hull with 25mm applique) Naval rule: 2.20" working equation: 2.28" three points regression: 1.88" 0.6" over 1.77" (T34 glacis with 15mm applique) Naval rule: 2.19" working equation: 2.21" three points regression: 1.95" 0.8" over 1.77" (T34 glacis with 20mm applique) Naval rule: 2.33" working equation: 2.37" three points regression: 2.01" 89mm over 89mm (Sherman Jumbo gun shield, no modifiers applied for cast armor deficiency to rolled plate) Naval rule: 151mm working equation: 146mm three points equation: 166mm 38mm over 64mm (Sherman Jumbo glacis) Naval rule: 91mm working equation: 85mm three points regression: 87mm The difference between the three approaches is due to the inclusion of a 90mm M82 projectile test in the three points regression, where two 1.5" plates in contact resisted as if they were a single 2.28" plate. The Naval rule predicts 2.55" and the working equation estimates 2.46". That point resulted in the equation depressing the overall resistance as the maximum plate thickness decreased below 2". [ 01-08-2002: Message edited by: rexford ]</p>

Back in 1999 Valera Potapov published some very interesting and useful data on his site regarding the development of the IS tank series that resulted in some of the problems that plagued the IS-2. Since some of that material is no longer on his site I would like to present the highlights of his 1999 presentation: 1. IS-1 tank with 85mm goes into production October 1943 and ends with 40 tank output during January 1944. This suggests that quite a few IS-1 tanks with 85mm gun were in action. 2. The IS-1 turret and mantlet were sized for the weight and gun associated with the 85mm main weapon. The 100mm turret front and mantlet allowed a perfect balance with 85mm weapon. The narrow mantlet also allowed good vision around the relatively narrow gun barrel that did not have a muzzle brake. 3. Starting December 1943 the IS-2 with 122mm gun was produced. Breech limited rate of fire to 1-1.5 shots per minute. Putting a larger gun in the turret unbalanced the turret to the point where the turret armor could not be increased without changing many of the turret rotation mechanisms, which was not desired (slows production). So turret armor is retained at 100mm max. Putting the larger 122mm gun in the narrow mantlet designed for 85mm gun creates problems seeing and firing on moving targets due to size of 122mm gun muzzle brake and distance from mantlet. Valera stated that it became all but impossible to use the telescopic sight, which suggests that the gunner had to use the turret top "gum drop" sight. The widened mantlet which shifted the sight to the left and improved telescope use was produced starting May 1944. 4. Starting January 1944 breech is changed on IS-2 allowing 1.5-2 shots per minute. 5. During March 1944, Russian firing tests conducted with 76.2mm gun firing on IS-2 tank from 500 to 600 meters. Tank's armor partially penetrated on all sides and while only a few rounds make it completely through, most hits create major splintering and fragmentation inside the turret. "This explains the considerable losses of IS-1 and IS-2 tanks in the winter-spring of 1944". Armor tempering improvements resulted from identification of problems. 6. IS-2 later version has 110mm at 60 degrees glacis, which is impossible target for Tiger II "88". Turret front armor at 100mm (rounded) is penetrated at 2000m and beyond by Nashorn in photo reports that I have. Russians realize that nose armor on later IS-2 tanks is vulnerable to 88L71 (we estimate that 88L71 APCBC penetrates 127mm at 30 degrees at 2500m, Panther penetrates at 500m), but believe that relatively few shots hit nose, and increasing nose armor slope would have major changes to driver compartment. IS-2 development and combat action sections on Russian Battlefield describe several penetrations of IS-2 nose armor. SUMMARY: IS tank development initially for 85mm gun, which creates some problems when 122mm gun is installed, and limits turret armor thickness. Nose armor is also limited by design considerations when uparmoring is pursued. IS-1 with 85mm gun could penetrate Tiger 100mm frontal armor at 1000m, but would be inferior to Panther.

My guess about the 122mm HE round is that AP hits were bouncing off the glacis armor beyond about 650 meters, and HE was a reasonable attempt to disrupt the crew or tank optics. Firing HE at a Tiger or Panther was always a decent tactic if one was cornered, 105mm or larger HE would blow off track pieces or damage wheels with near misses. The terrific impact from 122mm HE probably would crack some welds and might loosen some glacis plates. I would guess that maybe SU 152's starting hitting Panthers and Tigers with HE during 1943 and some of the damage suggested same tactic might work with 122mm HE. I will soon be sent some data regarding German weld material. The Germans used high carbon steel which can create welding problems. It appears that the weld material quality may have decreased during the war. Tiger II was supposed to use highest quality weld material. Lower quality weld material may have been used starting January 1944. American analysis of Tiger and Panther notes brittle nature of welds, hitting with a hammer can bust some welds. I'll ask about weld shapes on German vehicles, interesting questions.

Summary of previous post: 1. Panther glacis sound till summer of '44 (quality is 1.00 prior to that time) 2. Starting summer '44, Panther glacis appears to lose something resulting in more fragile nature and increased penetration ranges 3. Not well known what percentage of Panthers have deficient glacis armor 4. IS-2 tanks shoot AP and APBC from their guns in unknown mix, earliest IS-2 fire sharp nose AP exclusively, it would seem 5. Russians unaware of superior slope effects of blunt nose APBC until it goes through good quality Panther glacis at 1200m, when they run tests to see what is happening 6. Russian uncapped AP appears to use same slope effects as American and British solid shot AP: slope multipliers equal (^ raises term to immediate left by factor to right of sign): 65 degrees: 2.91 (T/D)^0.1864 45-60 degrees: (0.715 x 1.02^(angle))x (T/D)^(0.0779 x 1.0095^(angle)) 40 degrees: previous equation x 1.05 30 degrees: 45-60 degrees equation x 0.95 7. penetration tests at Kubinka suggest that Panther glacis loses more than 15% of resistance when it is hit by 122mm APBC, due to plate problems 8. Russian experience during summer of '44 consistent with U.S. tests at Isigny during August '44 and metallurgical analysis of one Panther glacis (low impact resistance and brittle structure)