rexford

Quite a few books, including Encyclopedia of German Tanks of WW II and Thomas Jentz' Panzertruppen, have published 30 degree penetration data for German weapons. The basis for the data can be found in the British BIOS report GERMAN STEEL ARMOUR PIERCING PROJECTILES AND THEORY OF PENETRATION, and it provides some interesting twists that are vital to proper use and understanding of the data for APCBC rounds (the thickness penetrated on half the hits should exceed the listed 30 degree figures). 1. German data is based on penetrations with HE burster intact and useful 2. An equation in abovestated BIOS report was used by Germans to estimate penetration at 30 degrees from vertical 3. Estimates are for best quality projectiles (specially made for tests or very best deliveries from standard production), where penetration estimates for average production ammo would require higher velocities to defeat a given thickness according to following figures: a. 5% higher for 75mm b. 3.5% higher for 88mm, 105mm and 128mm projectiles 4. Penetration versus velocity curve for 75mm, 88mm and 105mm projectiles based on obtaining five consecutive hits within a velocity range which result in a success (round passes completely through plate with HE burster intact). 5. The penetration resistance of German plate appears to vary quite a bit as hardness changes 6. The German critical velocity Gd is based on the criteria noted in note 4. above -------------------------------------------------------------------------------------------------------------------- To obtain five consecutive successes within a narrow velocity range as velocity increases, the probability that each round will succeed must be very high. For an 85% probability that five rounds will succeed in a row, the individual shots would each have an average 97% success rate. This means that German data is not comparable to American and British penetration data that uses 50% success as the criteria. To convert the German data to 50% success, the thicknesses would have to be increased by at least 10% (and possibly as high as 15%, subject to standard deviation size), which increases the penetration thicknesses above those shown on the tables even when the decrease to production ammo is considered. With regard to German armor hardnesses, the curves do not reflect the sudden changes in resistance which could occur as plate hardness changes in a step function with thickness variations. BIOS is the British Intelligence Objectives Sub-Committee, and the abovementioned report is BIOS FINAL REPORT No. 1343, ITEM No. 2, dated September 1945. The BIOS mission sent groups to Germany after the war (and maybe during the final stages as key areas were captured), interviewed key German personnel and collected published materials. 30 degree penetration estimates from equation in BIOS report follow for best quality ammo used in tests: 75mm APCBC 146mm at 935 m/s (Panther muzzle velocity) 140mm at 918 m/s (Panther ammo at close to 100m) 100mm at 710 m/s 88mm APCBC 200mm at 1003 m/s (88L71 at 0m) 180mm at 939 m/s 160mm at 886 m/s 140mm at 829 m/s 120mm at 763 m/s (Tiger 88L56 at close to 100m) 100mm at 680 m/s

Dima from this forum was kind enough to translate some Russian article statements for me that I found while cleaning out the long term debris in my download file (can't remember the source): "Page 1 One Pather (number on the side 441) after germans had retreated was put under test fire from 76-mm gun of T-34. There were a total 30 shots from the distance of 100m, 20 on Front Upper Hull and 10 on Front Lower Hull. Upper Hull was not penetrated, all shells ricocheted. Lower hull had only one penetration. Based on observation of knocked-out Panthers there was made a conclusion that they can be defeated by: a) Anti-Tank rifle aimed in lower side from 100m and less (with 90deg angle) Tungsten (it says undercaliber shell, this is how russians call these rounds I guess - DIMA) shot from 45mm gun - except aiming at the front of a tank. c) Armor-piercing shot from 76mm gun, except front side. d) Armor-piercing shot from 85-mm AA gun e) anti-tank mines (tracks) Page 2 Overall if we are talking about Panthers, they are quite good, even though there are some problems with starting the engine and its protection. Unlike that of Tiger, side armor is not invincible for 76-mm anti-tank shells. The tank's gun (Panther - DIMA) has exceptionaly good qualities." Tiger side armor IS invincible against 76mm anti-tank shells? Can't remember where the statements came from, I'am cleaning out my download files and occasionally come across some old but gold files.

Dima from this forum was kind enough to translate some Russian article statements for me that I found while cleaning out the long term debris in my download file (can't remember the source): "Page 1 One Pather (number on the side 441) after germans had retreated was put under test fire from 76-mm gun of T-34. There were a total 30 shots from the distance of 100m, 20 on Front Upper Hull and 10 on Front Lower Hull. Upper Hull was not penetrated, all shells ricocheted. Lower hull had only one penetration. Based on observation of knocked-out Panthers there was made a conclusion that they can be defeated by: a) Anti-Tank rifle aimed in lower side from 100m and less (with 90deg angle) Tungsten (it says undercaliber shell, this is how russians call these rounds I guess - DIMA) shot from 45mm gun - except aiming at the front of a tank. c) Armor-piercing shot from 76mm gun, except front side. d) Armor-piercing shot from 85-mm AA gun e) anti-tank mines (tracks) Page 2 Overall if we are talking about Panthers, they are quite good, even though there are some problems with starting the engine and its protection. Unlike that of Tiger, side armor is not invincible for 76-mm anti-tank shells. The tank's gun (Panther - DIMA) has exceptionaly good qualities." Tiger side armor IS invincible against 76mm anti-tank shells? Can't remember where the statements came from, I'am cleaning out my download files and occasionally come across some old but gold files.

German Tiger crews were expected to estimate target range within 10% of actual. If target is at 1000m, range estimates are expected to be from 900m to 1100m. Average British crews would look at a tank at 1000m and estimate ranges from 750m to 1250m. Picture it this way, you see a car and have to estimate the range. The more you practice and the better your instincts the closer you will be. Tiger crews were expected to attain very high accuracy in their estimates. I have stood in the streets of Albany New York and estimated the range to cars and poles, and then found the actual distance using a laser range finder. My average estimate error was 25%, just like the typical Allied gunner. The smaller the range estimation error, the higher the percentage of first round shots that hit the target if everything else is the same. Given the good ballistics of the Tiger gun and superior optics, a Tiger tank would have a higher accuracy than a 75mm Sherman, 76mm Sherman or T34 with 76.2mm. The Panther 75mm would be more accurate than the Tiger 88mm due to a higher muzzle velocity and flatter trajectory. The flatter the trajectory the less impact when range estimation errors are made.

The Russian feeling that Tiger E was equal to IS-2 is kind of interesting and may deserve a bit more discussion. IS-2 122mm AP is going to penetrate the Tiger E mantlet armor out to 1200m, and then it will fail against the mantlet but still be able to blow through any part of the front hull out to 1500m. Problem is low rate of fire for 122mm and ability to hit things. 6 to 7 rounds per minute for Tiger E with 10 kg projectile, 1.5 to 2 shots per minute for average 122mm crew due to 25 kg projectile that comes in two parts (weight of total round would be much greater than projectile due to casing and propellant). Tiger guidance indicates that 88mm HE could be used to blind IS-2 tanks after range is zeroed in by hitting turret, which would allow one of Tiger group to aim for turret. Tiger 88mm with APCR can penetrate IS-2 front lower hull at 1250m, and the turret front/mantlet at 2500m with a 30 degree vertical angle. Tiger gun is going to be more accurate, Tiger crews expected to estimate range within 10% of actual (average for Americans and British is 25%, probably higher for some Russians). Firing APCBC, Tiger penetrates IS-2 mantlet/turret front out to 1000m with a 30 degree vertical angle, but cannot defeat the front lower hull armor. Tiger E 88L56 is one of the most accurate guns of WW II in terms of low round-to-round scatter, 122mm is good but not quite up to 88L56 standards. Of course, 122mm HE could blow apart the welds on a Tiger just by hitting it, since it did that against Panthers. The impact shock from 122mm HE must have been devastating to crew members inside a target tank. If most tank combat takes place within 1200m, Tiger and IS-2 are pretty closely matched.

There is a report on the Russian Battlefield forum site at http://www.network54.com/Hide/Forum/message?forumid=116312&messageid=1040650225 that is worth reading in regard to Tiger II superiority over T34. Shows what can be done when overwhelming advantages are allowed to function free of Allied fighter-bombers and artillery fire. Three Tiger II knock out 41 T34 with German losses limited to gun damage.

Tiger in CMBB does better against 75mm Sherman APCBC cause the 75mm L40 APCBC penetration stats have been brought down to account for lower nose hardness, bigger HE burster and other factors. CMBO Shermans with 75mm APCBC are much too effective against Tiger side armor. Effectiveness of penetrating rounds in CMBB is also closer to reality. Not all penetrations that barely get through do much of anything. 76.2mm penetration of Elefant side at Kursk did nothing. Tiger is really a mobile fortress when it arrives on Eastern Front, send one out to meet 20 or 40 T34 and it blows them away even if they surround Tiger. That 82mm side armor is just too much. Try that with Panther and that 40mm to 45mm side plating. Russian ammo for T34 may be more variable in quality than game shows, CMBB appears to use Russian firing trial figures that represent best performance. T34 fired BR-350A and BR-350B APBC blunt nose ammo, 350A is very much less effective than 350B. When Tiger meets bunches of T34 they know that that 88 is going to effectively reduce their numbers in a short period, and they are afraid to close to 500m or less where their 76.2mm is effective (Russian tankers term closing within 500m as suicide against Tigers). Tiger fights after Stalingrad loss when Germans need psychological lift, and tank delivers. Russians feel that Tiger and IS-2 are equal in terms of fighting effectiveness, probably due to accuracy of 88 and its optics, plus a higher rate of fire than IS-2 (6 rounds a minute versus 1.5 to 2 for 122mm). CMBB also gives Tiger 88 the optical bonus it deserves. Tiger was an important tank and filled a need that PzKpfw IVF2, G or H could not fill.

The Americans had a heat of molten armor steel in a container, and they made plates from the top, middle and bottom areas. The bottom area plates were consistently more resistant than the top area material, with about a 10% difference in some cases (80mm of top area plate resisted like 72mm of bottom armor). The bottom area plates also had fewer impurities and flaws. The report suggested that impurities in armor are lighter than steel, so they rose in the container and were more heavily concentrated in the upper regions of the molten steel. [ December 04, 2002, 06:11 PM: Message edited by: rexford ]

Robert Livingston responded on another web site that impurities are lighter than steel, so they rose in the container. I believe that the Germans would make a plate from one heat of armor steel, and shoot at it (several shots had to be stopped without any cracks through the plate, and a few complete penetrations would then be made that had to show fully ductile failure). If the plate passed, the entire heat passed. If they chose to make the plate from the bottom of the heat, they would be testing the best material possible. The British BIOS report does not go into detail as to whether the Germans took material from any particular locations. The American drawings which were in the 1946 report show a big container which holds the molten steel, and the firing tests were conducted against material from top, middle and bottom areas. Material from the top would have more impurities and flaws, and would be about 10% less resistant than the bottom (80mm from top would resist like 72mm).

One of the U.S. reports we reviewed looked into the probability of armor deficiencies as a function of the metal location in the heat. It turned out that that the lower locations in a heat resulted in better armor all around, and the higher locations were associated with a higher probablity for flaws and reduced ballistic resistance. The bottom line from the tests was that armor would not necessarily be the same from plate to plate. It also suggested that when one plate from a heat passes acceptance criteria and an entire heat is accepted, which may have occurred in several countries during WW II, the test results might not be truly representative if it was drawn from the bottom (the best stuff). This may explain some of the wide variations in armor quality and performance that were experienced during WW II.

One of the U.S. reports we reviewed looked into the probability of armor deficiencies as a function of the metal location in the heat. It turned out that that the lower locations in a heat resulted in better armor all around, and the higher locations were associated with a higher probablity for flaws and reduced ballistic resistance. The bottom line from the tests was that armor would not necessarily be the same from plate to plate. It also suggested that when one plate from a heat passes acceptance criteria and an entire heat is accepted, which may have occurred in several countries during WW II, the test results might not be truly representative if it was drawn from the bottom (the best stuff). This may explain some of the wide variations in armor quality and performance that were experienced during WW II.

Some time ago, a poster asked about the diffrunt 37mm AP ammo used by the Germans, and how they performed. =============================================== 37mm L45 Pzgr was 0.685 kg and fired at 745 m/s. 30 degree Penetration = 35mm at 100m and 29mm at 500m =============================================== 37mm Pzgr(t), which I guess was fired by PzKpfw 35t KwK.34(t) gun, was 0.850 kg with 675 m/s muzzle velocity 30 degree penetration = 35mm at 100m and 30mm at 500m =============================================== 37mm Pzgr(t) from PzKpfw 38t KwK.38(t) gun, fired at 741 m/s with 0.850 kg projectile 30 degree penetration = 36mm at 100m and 31mm at 500m =============================================== Since all three 37mm rounds would have about the same slope effects, comparing 30 degree penetration results in about the same relative figures as converting to vertical(about a 1.30 multiplier to get from 30 to 0 degrees). German use of "t" designator appears to refer to Czech origin weapons and ammo. While 38t tank gun fires heavier round than German 37mm ATG, and at about the same velocity, penetration is not appreciably greater than German round due to projectile quality and/or size of HE burster(my guess). Source of data and information is Jentz' PANZERTRUPPEN 1943-1945 (Vol. 2, I think). None of the standard 37mm AP rounds is going to penetrate T34 45mm armor at 500m on other than a rare occasion.

Roughly about a year ago plus some months there was a discussion about how the Germans taught battlesight aim, which theoretically would result in a 100% hit probability from 0m to 950m against a 2m high target (level ground). At the time I offered some analysis which supposedly showed that the Tiger Fibel was incorrect, and that having the main gun above the target bottom would reduce hit chances. During a recent discussion on another web site regarding battlesight aim, I realized that my previous work and conclusions regarding battlesight aim forgot to change the angle from gun height to hull bottom as actual target range varied. I had used the 950m angle from gun to hull bottom at all target ranges, which suggested that the Tiger Fibel was incorrect. Turns out I was incorrect. The trajectory height and shape are roughly the same whether the Tiger gun is 1.64m above T34 hull bottom, or at the same elevation as Tiger Fibel appears to assume. Battlesight aim by a Tiger, as described in the Tiger Fibel, is when an aim range is computed where the trajectory will never exceed 2m above target hull bottom on level ground. A Tiger using a 950m battlesight aim would theoretically hit any 2m or taller target (measured from hull bottom) at all ranges up to 950m. When Tiger uses a 950m battlesight aim against a target at 500m, the gun is initially aimed straight at the hull bottom. This results in a downward angle of arc tangent (-1.64m/500m), or -0.19°. The gun is then elevated to the 950m range graticule on the scope, which adds +0.49° for a resultant elevation angle of 0.30° above horizon. My previous calculations used the 950m angle from Tiger gun to T34 hull bottom, which was -.10°, so the gun angle was overestimated at 0.39°. This overestimated trajectory height above target hull bottom. When I redid the calculations using the correct approach, the trajectory elevations above hull bottom with Tiger gun at same elevation as the T34 hull bottom were about the same as when the gun was 1.64m above the target bottom aim. So Tiger Fibel is correct! Gun location does not appear to matter with battlesight aim. Here are the trajectory heights and resultant accuracies from the correct analysis when Tiger uses 950m battlesight aim against a T34 on level ground (based on a simple physics approach that roughly approximates all figures): Target Range--Trajectory Height-Hit Probability 200m----------1.30m------100% 300m----------1.74m-------93% 400m----------1.96m-------56% 500m----------2.00m-------50% 600m----------1.85m-------66% 700m----------1.60m-------84% 800m----------1.03m-------98% 900m----------0.50m-------84% 950m----------0.00m-------50% Trajectory height is above hull bottom, and all calculations used a simple physics approach instead of detailed ballistics, so the results are very approximate. 2m target height is assumed from hull bottom to turret top, with infinite width. The hit probability is not 100% when the trajectory places rounds on the target since random scatter has been considered. At 700m, 68% of vertical dispersion is within 0.41m of the average trajectory height. When the average trajectory is 1.60m above hull bottom, distance from average trajectory to 2m high target top is 0.40m and 32% of the upward scatter passes over the target. None of the low scatter misses the target (assume infinite width to simplify the math). So the resultant hit probability at 700m is 84%. Tiger use of battlesight aim against targets at 0m to 950m will always place the average trajectory on the target assuming level ground, but random scatter will vary the hit probability from 50% to 100%. While battlesight aim appears to boost the hit probability against targets at 700m to 900m range, the hit percentages at 400m to 600m appear to be much lower than would be attained with center of mass aim and visual range estimation (Tiger crews were expected to estimate range within 10%, much better than the 25% figure associated with the average commanders visual estimate). Combat reports do not suggest that battlesight aim was always used by German tanks, and German tankers and ATG crews were often trained to aim at the intersection of turret and hull. Turret ring was very vulnerable, and it was said that 37mm PaK rounds could significantly damage a KV tank with turret ring hits: this may have lead to the use of added hull side plates to protect the KV-I turret ring area. It is not clear if American tankers during WW II were trained to use battlesight aim, none of the my U.S. tank crew manuals for WW II offer a first shot alternative to center of mass fire. Details presented for the few who are interested, others will get the gist by scanning the paragraphs and hopefully will not be sleeping when they get to this paragraph. Good night. [ November 26, 2002, 09:37 PM: Message edited by: rexford ]

During a recent discussion on another web site regarding battlesight aim, I realized that my previous work and conclusions regarding battlesight aim forgot to change the angle from gun height to hull bottom as actual target range varied. I had used the 950m angle from gun to hull bottom at all target ranges, which suggested that the Tiger Fibel was incorrect. Turns out I was incorrect. The trajectory height and shape are roughly the same whether the Tiger gun is 1.64m above T34 hull bottom, or at the same elevation as Tiger Fibel appears to assume. Battlesight aim by a Tiger, as described in the Tiger Fibel, is when an aim range is computed where the trajectory will never exceed 2m above target hull bottom on level ground. A Tiger using a 950m battlesight aim would theoretically hit any 2m or taller target (measured from hull bottom) at all ranges up to 950m. When Tiger uses a 950m battlesight aim against a target at 500m, the gun is initially aimed straight at the hull bottom. This results in a downward angle of arc tangent (-1.64m/500m), or -0.19°. The gun is then elevated to the 950m range graticule on the scope, which adds +0.49° for a resultant elevation angle of 0.30° above horizon. My previous calculations used the 950m angle from Tiger gun to T34 hull bottom, which was -.10°, so the gun angle was overestimated at 0.39°. This overestimated trajectory height above target hull bottom. When I redid the calculations using the correct approach, the trajectory elevations above hull bottom with Tiger gun at same elevation as the T34 hull bottom were about the same as when the gun was 1.64m above the target bottom aim. So Tiger Fibel is correct! Gun location does not appear to matter with battlesight aim. Here are the trajectory heights and resultant accuracies from the correct analysis when Tiger uses 950m battlesight aim against a T34 on level ground (based on a simple physics approach that roughly approximates all figures): Target Range--Trajectory Height-Hit Probability 200m----------1.30m------100% 300m----------1.74m-------93% 400m----------1.96m-------56% 500m----------2.00m-------50% 600m----------1.85m-------66% 700m----------1.60m-------84% 800m----------1.03m-------98% 900m----------0.50m-------93% 950m----------0.00m-------50% Trajectory height is above hull bottom, and all calculations used a simple physics approach instead of detailed ballistics, so the results are very approximate. 2m target height is assumed from hull bottom to turret top, with infinite width. The hit probability is not 100% when the trajectory places rounds on the target since random scatter has been considered. At 700m, 68% of vertical dispersion is within 0.41m of the average trajectory height. When the average trajectory is 1.60m above hull bottom, distance from average trajectory to 2m high target top is 0.40m and 32% of the upward scatter passes over the target. None of the low scatter misses the target (assume infinite width to simplify the math). So the resultant hit probability at 700m is 84%. Tiger use of battlesight aim against targets at 0m to 950m will always place the average trajectory on the target assuming level ground, but random scatter will vary the hit probability from 50% to 100%. While battlesight aim appears to boost the hit probability against targets at 700m to 900m range, the hit percentages at 400m to 600m appear to be much lower than would be attained with center of mass aim and visual range estimation (Tiger crews were expected to estimate range within 10%, much better than the 25% figure associated with the average commanders visual estimate). Combat reports do not suggest that battlesight aim was always used by German tanks, and German tankers and ATG crews were often trained to aim at the intersection of turret and hull. Turret ring was very vulnerable, and it was said that 37mm PaK rounds could significantly damage a KV tank with turret ring hits: this may have lead to the use of added hull side plates to protect the KV-I turret ring area. It is not clear if American tankers during WW II were trained to use battlesight aim, none of the my U.S. tank crew manuals for WW II offer a first shot alternative to center of mass fire.

Good points. Sherman 75mm APCBC penetration is downgraded in CMBB, so Tiger side armor is not as vulnerable at 500m (and beyond) as it was/is in CMBO. Another point in Tiger favor. In close country, like France, Tiger side armor buys ALOT of survival ability compared to Panther side plates, especially against 75mm armed Shermans. Against a 76mm armed M10, Tiger shifts into the 45 degree facing to firer, and the front and side armor cannot be penetrated in pre-HVAP days.

Reading through accounts of Michael Wittmann's death, couldn't find range info. Or missed it (I'am near retirement age and things go by so fast). Anyone out there familiar with the ranges involved in the destruction of Wittmann's last Tiger? Would appreciate some help with this. I remember (subject to many failings) that the Sherman crews with 75mm guns were not enthusiastic about their chances, they believed that their ammo would bounce off the Tiger sides. And that the 75mm Sherman hits did bounce. This inquiry is really related to T34 performance against Tiger side armor. T34 76.2mm APBC penetrates 81mm at 500m, Sherman 75mm APCBC penetrates 82mm at 500m. Just trying to see how one round did in actual combat against Tiger side, and then guessing what other would do. Russian Battlefield vet interviews stated that T34 would defeat Tiger side armor at 500m or less, but closing to that range was considered suicidal (suggests T34 crews might be afraid to get that close to a Tiger). Thanks for any help that is offered. [ November 24, 2002, 06:26 PM: Message edited by: rexford ]

Thanks for response. Posted the whole article for those few (very few) who would be interested in little details. My long post adds some credence to T34 76.2mm APBC penetration against Tiger side 82mm, suggests that armor could be defeated at just under 500m if gun is lined up to hit armor face to face. Some Russian tanker anecdotes state that T34 could penetrate Tiger side armor at 500m, but that range was considered suicidal and it would seem that few T34 dared to approach that closely. There are German maintenance and field reports where Tigers were hit many, many times by 76.2mm and 57mm Russian rounds without a single complete penetration. Tigers in these combats appear to have been surrounded. Given the penetration data for 57mm and 76.2mm guns, where 57mm penetrates 102mm at 500m and over 90mm at 1000m, one might wonder how 57mm hits could land all over a Tiger and not penetrate. At Kursk, 76.2mm rounds from ATG and tanks hit the side of a Ferdinand many times at 300-400 meters range before one round penetrated without much effect. The above info suggests that while Russian APBC could penetrate 80mm test plate, something may have been happening in the field to reduce projectile effectiveness. Maybe the rounds were shattering when penetration was in excess of that needed for 50% success, or were not of the highest quality. Some German documents suggest that T34 APBC rounds could not penetrate the Tiger side armor at 200m, based on Russian tests. German records for Tiger units usually indicate no 76.2mm penetrations. Many folks have questioned 37mm ATG penetrations of the T34 turret front during 1941 and 1942 combat, I wonder if T34 defeat of Tiger armor strikes anyone as optimistic.

The WW II Russians used anti-tank projectiles which were unlike those in use anywhere else due to their flat nose and relatively low hardness. The true performance of the rounds was somewhat masked by official wartime Russian penetration figures for their flat nose APBC rounds (BC indicates a wind screen), which were based on DeMarre estimates against cemented plate and found their way into German and British intelligence reports. Much speculation has surrounded the performance of the flat nose Russian projectiles. British and American theory held that the flat nose would dig into sloped armor and counter ricochet forces, improving performance on angled hits. However, tests with 20mm projectiles and some full size 75mm versions suggested that the flat nose rounds had trouble defeating vertical or sloped armor thicknesses 10% greater than their diameter, due to nose shatter. U.S. firing trials with 100mm and 122mm Russian flat nose APBC rounds offer a view into how those rounds actually work, which supports some theories and counters other concepts. The 122mm APBC penetration curves cover angles from 0 through 70 degrees impact (rolled armor targets), and are based on Aberdeen Proving Grounds report DPS-647. At velocities from 2200 to 2600 fps, the vertical target penetration of the 122mm projectile increases as the velocity raised to the 2.5 power, and varies from 135mm to 206mm. The overall shape of the curve suggests that shatter did not occur. Against 60mm plates at 60 degree slope from vertical, the 122mm APBC slope effect is 1.58 and the sloped armor resists like 95mm at vertical, less than the see through horizontal distance. The 122mm tests support the theory that flat noses boost sloped armor performance, and counter the theory that flat noses are prone to penetration robbing shatter against thick armor . The 100mm APBC tests present some different results from the 122mm, and are based on APG report DPS-1661. From 2200 through 3000 fps, the tests against vertical cast armor relate vertical penetration to a near linear function of velocity (132mm at 2200 fps, 157mm at 2600). The smooth shape of the 0 degree curve suggests an absence of sudden shatter as thickness increases, but the reduced penetration increases may signal increasing projectile damage. The sloped armor penetration of the 100mm APBC, at angles from 30 to 75 degrees, appears to be consistent with the 122mm APBC trials when cast armor is converted to rolled equivalent. This suggests that the 100mm round is suffering damage against vertical and near-vertical targets as thickness/veocity goes up, but is performing like the 122mm against sloped armor. While the 100mm and 122mm APBC curves may be based on post-WW II ammo, they were used to predict the vertical penetration of WW II Russian flat nose ammo agianst rolled armor (cast thicknesses coverted to rolled equivalent). Comparison with WW II Russian trials resulted in some surprising results. When 100mm APBC penetration was used to predict 57mm and 76.2mm APBC at 0 degrees, the following comparisons with WW II Russian tests were prepared: 57mm BR-271 APBC with 990 m/s muzzle velocity 100mm APBC based prediction: 104mm at 500m, 93mm at 1000m, 84mm at 1500m Russian tests: 102mm at 500m, 95mm at 1000m, 84mm at 1500m 76.2mm BR-350B APBC with 2148 m/s muzzle velocity 100mm APBC based prediction: 87mm at 100m, 81mm at 500m, 74mm at 1000m, 67mm at 1500m Russian tests: 90mm at 100m, 80mm at 500m, 73mm at 1000m, 66mm at 1500m The 122mm APBC estimates for 57mm and 76.2mm APBC were not as good as the 100mm based predictions, and were up to 45% different from the 57mm test results. Russian test data for 45mm, 85mm and 152mm APBC appears to be consistent with 122mm APBC based estimates, and the 100mm APBC based figures do not compare well for those rounds. The above data and results suggest that Russian APBC may be prone to damage effects based on shape, since the 57mm, 76.2mm and 100mm APBC projectiles differ substantially from 122mm APBC and appear to follow different penetration equations at low angles. 76.2mm APBC has about 40% of diameter as flat nose while 122mm has about 20%, and the 57mm and 100mm APBC are relatively longer than the 122mm APBC for their width even though relative flat nose width is about the same. The trials with 20mm and 75mm flat nose rounds that observed severe nose shatter were made with projectiles where the flat nose made up about 85% of total diameter, which supports the theory that shape may be a critical factor for flat nose projectile effectiveness. While the 100mm and 122mm APBC results may be based on post-WW II ammunition, the curves appear to be consistent with WW II projectile performance.

Which helps you how?</font>

While it appears that 100mm APBC did not make it into WW II (although jury is still out), following shows an interesting aspect of ammo quality. The post-war tests (we think they are 1960ish)show that the round lost penetration against vertical armor as velocity (and thickness) increased, suggesting damage to nose. The results also suggest that U.S. cast armor was of reasonable good quality. The 100mm APBC appears to show the low slope effects against angled armor that we found with 122mm APBC, and damage to the projectile on angled hits did not appear to be a significant consideration. At 2600 fps impact, 100mm APBC penetrated 102mm of cast armor at 55 degrees, where the cast armor resists with 91% of rolled armor effectiveness. The slope effect works out to about 2.00 comparing rolled armor equivalence. If 128mm APCBC hit 100mm cast at 55 degrees, the expected slope effect would be about 2.29.

The probability of hitting a tanks' tracks is greatest when front of vehicle is at 30 degrees angle to the firing gun aim, which places the front track area in direct line with the gun barrel (below the center of mass). As range increases, ground folds (small rises and valleys) tend to block out a firing guns line of sight to the bottom areas of the target tank (tracks and front lower hull). At Isigny, firers had trouble seeing enough of the Panther front lower hull armor to hit it and ranges were 200 to 800 yards. If they couldn't see the front lower hull well in very case, they couldn't see much of the tracks either.

When the IS-2 glacis was uparmored from 105mm/30 degrees to 110mm/60 degrees,and the nose armor went from 95mm to 127mm at 30 degrees, why wasn't the mantlet and turret front armor significantly boosted in resistance? Because the IS-2 turret was unbalanced by the large gun, and adding more weight in the form of armor would have played havoc with the whole affair. The flat area underneath the T34 gun is pretty far out on the barrel and contributes a given moment about the gun rotation point. Add weight and things might not work well anymore. This is similar to PzKpfw IVH not having turret front/mantlet armor increased when front hull goes from 50mm to 80mm. Why put 82/55 degrees on Panther glacis, which resists 17 pdr APCBC like over 200mm vertical, when the mantlet has 100mm cast? It's all related to weight. The flat area may be a good target to aim at at close ranges but trying to hit it at 800m is probably going to expend more effort than it is worth. How big is that flat area in a gunsight at 600m? German crews trained to aim at intersection of turret and hull, where even a 37mm AP hit could damage the turret race on KV and T34 tanks. We have compared the results from our ballistic model to combat results and they are close. At close range, when one aims at the center of mass (T34 or Panther glacis), very few shots will strike the turret because: A. shot to shot scatter is extremely small B. variations in aim point are small C. errors in range estimation are small and round tends to hit close to aim point D. trajectory is flatter at close range so errors in range estimation have less effect on vertical placement of shots We have read about a 75mm armed Sherman that was firing on and hitting a Panther on the glacis at close range. After this went on for awhile the Panther commander spotted another Sherman to his flank and rotated the turret onto the second Sherman and drilled it. While the Panther was rotating its turret and firing the first Sherman kept hitting the same glacis area, shot after shot. How many wargames decrease the percentage of total hits that land on turret as range decreases? And the percentage of track hits that occur at close range will be small, compared to longer ranges, when a tank is pointed directly at the firing gun. Due to abovenoted reasons. Our wargame took over 15 years to develop and is based on alot of research and analysis.

Originally posted by Mike: "Lastly I can't believe Rexford used his wargaming experience to justify something!! Man that's something I only ever do in extremis, and then only in terms of what the rule author thought something was and comments about the autor's reputation." First off, aim at T34 front will vary from exact center of mass, and that was mentioned in my post. We use a miniatures system where shot location is measured on a model from the aim point, and takes into account random shot scatter, scatter of gunner aim point, range estimation errors, stupid errors due to human factors, etc. The experience with our wargames was that the T34 turret front area was getting hit alot on that vertical piece below the gun barrel. This lead us to look into whether it was realistic to have that many hits land on the vertical piece below the barrel, and it appeared to be logical after we analyzed the situation. The wargame bit was brought up as part of our examination of how often the vertical piece should be hit. When someone says wargame during a research debate, many people discount the findings or conclusions that are drawn. It's expected. We have the most realistic and accurate wargame system for individual shot resolution (whether it hits, where it hits and what it does), and it is occasionally used to help answer questions on this forum. If someone says alot of T34 turret side armor is visible on turret front shots and about 50% of the shots should bounce off the turret sides, we take our wargame model and I roll the dice 400 or 500 times and tabulate the results. I did this on an earlier thread. Each roll results in a vertical and lateral drift of the round from the aim point which takes into account all of the factors mentioned above. I also have a computer program which does the dice rolling and range estimating and everything else and outputs shot location from aim point. Most of the turret hits were bunching up around the vertical center (middle of left to right dimension) at 800m, but quite a few did hit the turret sides. We did the tests with a 75L48 APCBC round which has alot of scatter.

85mm APBC drives a plug into the tank interior that is as wide as the projectile, whereas German 75mm APCBC burster may not explode (they usually didn't in some German tests with angled hits) and the armor breaks off in smaller pieces. A partial penetration by 85mm APBC probably drives an 85mm wide plug into the tank interior, while 75mm APCBC partials send fragments and less of them than 85mm. 85mm APBC also makes a bigger hole, and has a bigger HE burster. German 75mm APCBC has 0.2% of the weight as HE burster, which is one of the smallest percentages for a WW II armor piercing HE round. German 75mm APCBC has 0.03 pounds of explosive.

Jeff, Your statements are so vague that it is difficult to see what you mean. Put up some numbers from the info you have so we can see what you are talking about. And stop throwing around accusations that are not supported in the same post. And please stop saying that what you have is correct and everything else is in error. We checked our penetration estimates against all sorts of data and they appeared reasonable, you have one trial that you may be misinterpreting for all I know. The Russian velocity decreases with range that I use are based on Russian figures we obtained, ballistic equation estimates and other approaches. You may not know this but practically all WW II velocity estimates vs range are based on ballistic equations, and the results can vary by quite a bit. Use a different methodology and obtain a different number. "This is reinforced by the fact that the boundry conditions for your three equations are velocity dependent." What the heck does that mean? Another comment that is impossible to interpret. When velocity is 2200 fps, the equations for 2200-2600 fps and 1800-2200 fps penetration result in 135.6mm and 134.3mm. When velocity is 1800 fps, equations for 1800-2200 fps and 1400-1800 fps result in 93.5mm and 94.1mm. I curve fit through areas of the curve that appeared to have the same relationship between velocity and penetration. "In the mean time you should really consider digging up actual firing tables rather than trying to guess what the decay is." Which is what we have done, and we filled in the empty areas with other estimates, and then turned the data into spreadsheet friendly equations. "I believe I have indicated on several occasions where this material can be found." Nonsense. No specifics, just like your posts. "You should also be aware that recently obtained source material indicates that significant hardness changes occurred in Soviet AP between the end of WWII and the mid-1960’s. This would suggest either different metallurgy and/or different manufacturing processes were being employed by post-war Soviet ammunition industry. Using AMMRC data from 1972 “firing trials” (or should I say graph) to represent circa 1941-1945 penetration figures is questionable." We were keenly aware of this possibility when we received the 122mm APBC curves about two years ago, long before you received data that suggested it. That's why we thoroughly tested the estimates from the equations before we accepted them for use in the book. You have totally missed the point on all the material published in our book and on various forums to explain why using post-WW II trials with 122mm APBC appears to be a reasonable approach. While what you say sounds reasonable, use of the 122mm APBC curves results in estimates that closely match Russian figures from 1940 and 1943-1944 tests, post-WW II firing tests against captured American armor, etc, etc, etc. Until you post some real data and information that clearly shows that my numbers are rubbish, what you say has no real validity. Our figures for T34 76.2mm BR-350B are close to Russian figures from WW II but lower. If you have something that shows that they should be even lower, put it on the table so we can look it over and see if it is as "correct" as you assume. I posted my methods and info so you, and others, could critically analyze it and challenge it (which you've done without being specific), why don't you do the same? [ November 13, 2002, 08:01 PM: Message edited by: rexford ]