rexford

Spanish Civil War experience with tanks showed that hard armor increased casualties, as armor would splinter and send jagged pieces flying about after penetration. Kind of like breaking a piece of glass with your foot. Russian tanks with soft machine quality armor (able to be machined by normal equipment) would be penetrated and crew would walk away if projectile didn't hit them on fly or something else didn't explode. Hard Krupp armor on PzKpfw I and II would take crew members on penetrations due to flying fragments. But observers of war in Spain noted that Russians quickly went back to hard armor. Might have been a fear of 20mm and 37mm penetrations that hard armor would help defeat. Armored cars generally use very hard armor to defeat bullets and HE fragments, which minimizes weight and helps keep speed up. T34 with 76.2mm gun seems to be based on speed, keep armor thickness down, keep crew area down, slope plates to maximize resistance, etc. High hardness maximizes resistance against 37mm and 50mm ammo, in theory. Instead of thicker turret front armor, look at a Model 1941 or 1942 T34 turret and you'll see that it is shaped to minimize frontal area and maximize rounded shape to help ricochet hits. Make turret front small and curved to cause misses or deflections. T34 is designed to give it speed and the ability to run through a defense. KV-1 is the opposite design. Big thick soft plates that can be hit many times by 75mm and larger projectiles and the plate won't shatter, crack or break when it defeats hits. KV-1 and KV-2 tanks that held up Germans during 1941 took 50mm, 75mm and 88mm hits and penetrations and the crew stayed and fought on. Thick soft armor aborbs projectile energy as plate material is pushed out of the way, and even when it is penetrated round often is broken up or has little energy left. Thin hard armor at an angle is penetrated by busting up the plate in front of the projectile, which often tends to send those jagged pieces flying about. Even when hard armor at an angle defeats big caliber hits it might still crack or send a disk of armor flying back at the crew. Panther glacis was often brittle and cracked at Isigny when 17 pounder hits bounced at close range, which is what happens when soft machine quality armor is brittle and tends to react like high hardness. T34 armor is not meant or able to take repeated hits from medium or high velocity 75mm rounds, it just doesn't have the impact aborption. KV-1 and KV-2 armor is. T34 design centers about speed and giving it the ability to move quickly through a defense. There are stories about the ability of KV-1 to waddle through an obstacle course or even cross a bridge without destroying things as its steering prevents straight movement. Nothing published states the design philosophy behind T34 and KV-1, but all of the armor characteristics and shapes suggest different battlefield roles that called for different armor thickness, slope and hardness considerations. P.S. The inability of T34 crews to see to the sides and rear is a real big problem, especially since the Germans specialize in flank ambushes where panzers draw out enemy and then withdraw, with hidden anti-tank guns to the side of advance. German panzer crewman who were captured told Russians T34 is blind to the side, side viewing glass has bubbles and does not magnify. Russians respond by adding cupola to T34. Tank that is moving up to and through enemy lines doesn't need good side vision, in theory. Until they realize that ambushed on way to enemy positions is causing too many casualties.

The IS-2 and IS-2m tanks used high hardness armor everywhere but the 90mm vertical side hull, based on American analysis of tanks found in Berlin ruins. We do not have any hardness for ISU vehicles and T70 and many others, but the trends developed for the tanks we do have data on point to certain thickness-vs-hardness criteria based on period of war.

During our research we found German test firing results for 50mm Pak against KV-1 tanks. KV-1 has 75mm front hull armor at 30°, and 50mm Pak penetrated this at 100m and failed at 200m in actual tests, so actual range for 50% success is in between 100m and 200m. From our books' perspective, 75mm armor at 30° resists 50mm APC hits like 96mm at 0°. 50mm L60 APC penetrates 96mm at 190m on half the hits, which is in same ballpark as test results. KV-1 armor was machine quality, 250-300 Brinell. Early model KV-1 ('41 and first part of '42) was vulnerable to 50mm Pak on side shots, with 75mm side armor (hull and turret) which could be penetrated out to 700m by 50mm L60 APC. Since Germans often tried for side shots and ambushes to reduced losses, 50mm Pak would be very effective against KV-1 tanks. T34 with high hardness armor has greater resistance than KV-1 front hull against 50mm Pak, and might laff off hits. T34 glacis resists 50mm hits like about 112mm at 0°, KV-1 like 96mm at 0°. From Russian miniatures gamer perspective, T34 armor is great against 50mm Pak and KV-1 is going to get penetrated at close range on frontal overrun attempts. Later KV-1 adds high hardness plate to front hull armor, which makes KV-1 more difficult to defeat frontally than T34 when they are attacked by 50mm Pak and 75L43. Robert Livingston took notice of fact that 30mm plates added to KV-1 front hull were high hardness, and T34 45mm armor was high hardness, and several other armor tidbits (including T34/85 and SU 85), and a pattern appeared that is discussed in our book. All Russian armor of 60mm thickness and under is high hardness in every case we have observed. Whether 1941 T34 or 1945 T34/85, with SU 85 and others in between, thinner plate and cast armor is high hardness. Probably designed to maximize resistance against 50mm Pak. Starting in 1944 Russian use high hardness on all castings, based on the materials we have reviewed. So T34 is always vulnerable to 75mm hits at fairly good ranges due to brittle behavior of very hard armor. Airplanes use face-hardened armor to get the most bang from the millimeter against cannon and machine gun fire while keeping plane weight down. T34 appears to have used the same logic, the tank is designed for rapid penetration and not for trading shots with German panzers using 75mm and larger guns, so armor is designed for maximum resistance against the small anti-tank guns used by Germans in rear area defense (37mm and 47mm and 50mm). This is our theory based on looking at armor resistance. KV-1 is a heavy tank designed to trade shots and win, so armor is thick and is machine quality which will not be so brittle when a 75mm or 88mm round bounces off. T34 armor quality may be a non-issue against 75mm hits due to brittle behavior by even the best plates and castings. [ 07-02-2001: Message edited by: rexford ]

John, Please state what it is we don't agree on, as it is not clear. My point is that T34 armor will almost always be very brittle due to high hardness, and will lose gobs of resistance when 45mm plates are hit by 75mm projectiles. 1. British, American and German armor analysis show T34 armor to be high hardness, Germans say always over 400 Brinell, which agrees with American analysis. Germans analyzed MANY T34 prior to their 1942 report, so we're not talking a hand full of Allied reports. 2. 45mm high hardness armor ALWAYS loses about 25% of its' resistance against 75mm hits, regardless of quality 75mm L43 should generally not have any problems penetrating T34 glacis below 1000m, and many times out to 1200m or further ranges. 3. T34 armor varied in quality from great to poor, which may have varied resistance by a little bit (high hardness makes it poor against 75mm as general rule, so poor quality makes poor resistance a little poorer) 4. Some T34 had add-on armor, which would increase resistance by a small amount. 5. As a general rule, there is no evidence that any factories used 50mm to 55mm thick plates on T34 glacis as design rule, or lowered design hardness to 250-300 BHN. 6. T34 used different turret designs.

German tests with 37mm and 50mm guns against T34 armor (same composition and hardness) showed that 50mm Pak could penetrate 45mm at close range and many steep angles but not at 60°. Our book has 101mm penetration for 50mm Pak at 100m and 0°, with a 3.1 slope effect against 45mm armor at 60°. So T34 armor resists 50mm hits like 45 x 3.1, or 140mm. High hardness armor modifier brings resistance down to about 117mm. Based on calculations, 50mm Pak should not penetrate T34 glacis using APC ammunition. [ 07-02-2001: Message edited by: rexford ]

U.S. also tested T34/85's found in Berlin ruins, and an SU 85. Russian armor made out of same stuff, designed for 400+ Brinell Hardness, and can only get worse than standard high hardness armor. High hardness armor is like glass made out of standard window stuff, no matter how carefully it is made it is still brittle and can't take large impact.

The 250-300 BHN possibility for T34 glacis was not suggested by anyone else, I brought it up to show that it is not logical to assume some factories varied tremendously from design directives. T34 armor quality is kind of a non-issue for high hardness armor, cause the armor loses tremendous amounts of resistance when 45mm plate or cast is hit by 75mm ammo. High quality armor at 400 Brinell Hardness loses over 20% of its resistance on 75mm hits against 45mm armor, based on American and German tests. Germans tested ALOT of T34's and found armor hardness to be above 400 BHN. German penetration cards against T34 do not take high hardness armor into consideration, they are based on straight calculations assuming T34 armor resistance equals German penetration data basis. T34 glacis hit at 30° side angle has compound angle of 64.34°. T/D =45/76.2, or 0.59. Slope effect is 3.30, hardness multiplier is 0.76. Armor resistance is 45 x 3.30 x 0.76, or 113mm at 0°. 76.2L51.5 APCBC penetrates T34 glacis on hit with 30° side angle at 800m when high hardness armor is considered. If T34 armor is treated as machine quality armor at 250-300 Brinell, penetration range on 30° side angle hit is "none" (148mm armor resistance, 136mm penetration at 0m). German gunner card tells crews 100m on 30° hit, actual battlefield experience would result in well over 500m. Americans prepared penetration range data prior to Normandy that said 76mm could handle Tiger out to 1000 yards or more, Baily's Faint Praise indicates 50 yards was about it. Penetration range estimates prepared in the safety of an office far from the front can sometimes be off by quite a bit. German penetration cards for Sherman are also rather pessimistic, don't consider armor flaws and cast armor deficiency.

High hardness armor in 45mm thickness is going to react in a brittle manner when it is hit by 75mm rounds regardless of whether it is good or bad quality high hardness. And high hardness armor in 45mm thickness will lose much of its resistance when it is hit by 75mm rounds, regardless of relative quality. High hardness armor has low impact resistance, and loses resistance against overmatching round (diameter greater than thickness). The quality of high hardness armor that is overmatched by projectile hit is a non-issue most of the time.

I have a German report from mid-1942 where they analyzed T34 armor based on their extensive captures, and they reproduced the armor for firing tests using 37mm and 50mm guns. The hardness they used as representative of T34 tanks was 430 BHN. So now we have EVERY American and British analysis that can be found, and EVERY German analysis that can be found, showing high hardness. High hardness sounds right, and brittle behavior against 75mm hits.

Lower velocity often results in thinner shell walls and more fragments per unit area. This is why U.S. 75mm HE puts out a higher number of effective fragments than 76mm and 90mm HE, and comes very close to 105mm output at distances close to detonation.

If some T34 had machine quality armor hardness, they must have been poor quality to allow 1000m penetrations. Factories vary? T34 armor was about 45mm thick in all cases. Lowering the hardness to 250-300 BHN requires additional steps, in many cases. Based on penetration range threads that have taken place in the past, there is no evidence that T34 had good quality machine quality armor. And if they did have machine quality the resistance was bad. With good quality machine quality armor, T34 glacis has 122mm at 0° resistance vs 75mm hits. That's more resistance than Tiger driver plate! Could T34 armor resistance have been variable? Yes. Good quality high hardness, penetrated to 1200m to 1600m. Poor quality high hardness, penetrated to 1600m. Good quality but hardness between 350 and 400 BHN, penetrated to 1000m max. Poor quality but 350-400 BHN hardness, penetrated to 1200m to 1600m max. Russians were trying to pump out as many T34 as possible, would someone take time to lower hardness? Maybe not but plant could use tempering procedures and produce hardness in 350-400 BHN range. This armor would have more resistance than 450 BHN, especially at 375 BHN. There is no evidence that T34 armor was ever good quality machine quality in 250-300 BHN range.

Regarding Russian high hardness armor, Robert Livingston did a very extensive study of all available BHN data and came up with a table that cross indexes armor thickness with year. The result is a BHN figure. If T34 glacis is 250-300 BHN and good quality, resistance equals 122mm at 0° against 75mm hits. This limits 75L43 penetrations to 500m. There are no reports anywhere that limit 75L43 penetration of T34 glacis to less than 500m. Some say 1000m, some say any angle at 1200m and out to 1600m max, but none say less than 500m. Every T34 and T34/85 that was analyzed by Brits or Americans was high hardness. SU 85 glacis was high hardness. All of 'em. Every IS-2 was high hardness except for 90mm vertical side hull armor. Thin plates on KV-1 were high hardness but thicker plates were machine quality. Take a few tanks that were analyzed and ALL are high hardness, look for evidence of 75mm L43 penetration defeats just beyond 500m and find none, find penetration ranges that support high hardness, and it is more than reasonable to assume all T34 and T34/85 are high hardness. Some of the high hardness T34 are poor quality. Spanish Civil War reports have Russian tanks using softish armor which reduced crew casualties, but then Russians revert back to high hardness. We looked at this issue long and hard over a 15 year period and came to the conclusions noted above. Our book assumes that T34 is high hardness, and uses Livingston's table. At this point we say if someone feels that some T34 were hardened to 250-300 BHN, show us the defeated hits at 500m. When we deal with WW II we are dealing with limited and incomplete data, and one must draw conclusions using many different approaches. We did this. Regarding Poldi portable BHN machine, the fact that it is portable may lead to low estimates of armor hardness. [ 07-01-2001: Message edited by: rexford ]

And then there is smokeless powder. Read where Brits on hill were fighting German tanks camouflaged in woods, and Brits could not see where tank guns were due to no tell-tale clouds. Brits took a pounding. Only give-a-way was when trees and brush on tanks moved due to weapon blast effects.

If guns are 88L71 kill total should increase above 88L56. Germans would also know fairly well that one hit on a Sherman is enough, so they might change targets faster than they would against an IS-2m or Sherman Jumbo after a hit without smoke or flames. Hit the Sherman, move on to next target. If all Shermans at about the same range, one doesn't even have to change range setting of 88, just move gun over to adjacent Sherman and blast it back to Normandy! Low kill rates seem realistic, NOT!!!!!!!!

88 ground mounts should have a really high rate of fire compared to tanks, which is one of the reasons why 88 Flak units might be expected to torch alot of Shermans. 88 ground mount is also relatively flat trajectory compared to 75 on Sherman, but low velocity HE fire is easier to bring onto a target then higher speed HE. Higher rate of fire of 88 ground mount and bracketing use, plus first fire, plus possible recon of terrain for range card use, plus likely use of range finders, means that a handful of 88 kills before they meet their end sounds bogus, dude!

U.S. Army TM9-1907 has penetration data for HE explosions as a function of distance from blast. Might be interesting to compare the figures to armor on halftracks and armored cars. HE penetration data might be against soft steel, whereas thin armor on lightly armored vehicles is usually very high hardness (designed to defeat regular bullets and HE frag). I'll dig out my HE tables.

If the armor is going to be hit by high velocity shell fragments after a ground hit and there is a danger of some or most piercing the armor, then slope would have a large effect. Armor hardness would also be a factor against HE fragments, the harder the armor the better against small pieces of shell. British and American tests show that slope effects are more pronounced for smaller projectiles. The Germans face-hardened their anti-tank gun shields to defeat bullets, and the extra surface hardening might help against HE fragments. British ATG shields were not face-hardened and tank MG bullets pierced them in North Africa. U-Boat conning towers were reportedly face-hardened to help defeat 20mm aircraft cannon rounds. Aircraft also carry face-hardened armor.

U.S. tankers often did not know much about their weapons against panzer armor. 76mm armed tanks in France were told Tiger was mincemeat at 1000 yards, actual range more like 50 yards. PzKpfw IVH has face-hardened front hull armor so comparing homogeneous penetration of Sherman 75mm to IVH armor underestimates penetration probability and range. Same thing for Panther side armor, which is face-hardened on D and A versions. There are combat reports where 75mm Shermans kept on bouncing APCBC off Panther glacis for shot after shot. For whatever reason they probably thought a hit should be a kill. In the report where the 75mm Sherman kept hitting the Panther glacis, the Panther crew realized the fixation of their attacker and rotated the turret to take on another threat while the first Sherman kept on scoring hit after hit (to no avail). One of the great things about CM is that one may have an inkling of what is a vulnerable range and armor angle, but you can't be sure. In armor miniatures you can position Tigers so 75mm Sherman are 3° degrees outside the penetration cone, in CM this is near impossible to do with high precision.

Our book has equations that can be used to relate penetration to range, and armor slope effect to angle. This is what has to be done to prepare a penetration calculator. We also have an Excel spreadsheet that takes input in form of a gun/ammo number, a range and the armor thickness/angle and uses "vlookup" functions to do all the intermediate steps, and the computer even rolls the dice against a penetration probability curve and determines if the hit penetrates. A penetration calculator for CM is very do-able using a spreadsheet, but may not provide enough of a challenge for a masters program. I have armor resistance multiplier programs on my programmable hand calculator, and it is very simple once slope effect is tied into the T/D ratio (armor thickness divided by projectile diameter). The problem is converting data to equations to automate process.

Regarding those penetration range figures for Russian guns and ammo against Tiger II, following is side angle associated with hit, just so it doesn't appear that 85mm could only penetrate Tiger II at 500m or less regardless of lateral angle. All hits are against 80/20° or 80/25° side armor unless noted otherwise. 45 APCR hits at 0° side angle 57 APCR hits at 30° side angle 57 AP hits at 30° side angle 76 APCR hits at 0° side angle 76 AP hits 80mm/0° side armor at 0° side angle 85 AP hits at 30° side angle It would seem that the firing tests were conducted on a 600m long area. If 85 gun used APBC, then penetration range is limited by shatter gap since 85mm APBC penetration/armor resistance ratio at 500m and 30° side angle is between 1.20 and 1.25.

The Russian Battlefield and Valera's entries therein have not been uniformly pro-Soviet and are objective:. ------------------------------------------- IS-2 armor so brittle and flaky 76.2 APBC was able to partially penetrate all sides from 500 to 600 meters, with bad fragmentation on inside even though no complete penetrations. This is why so many IS-85 and IS-122 tanks lost. 45mm APBC ammo very poor during several month period during '41-'42. 100mm APBC so poor gun could not be released for use until after a lengthy delay improving ammo. 57mm HE ammo poor quality. Low rate of fire for IS-2, 1 to 1.5 rounds per minute for first models (why would pro-Russian sources want this rate of fire pointed out?). 122mm initially fires AP rounds (BR-471) at Panther and they bounce off glacis. SU-76 has many problems and is not well liked. ------------------------------------------ We analyzed all of the firing test data and combat claims on the Russian Battlefield site and, for the most part, they make sense. We have U.S. tests of 122mm APBC at angles up to 70°, and have estimated other APBC rounds from 122mm data. This data was used to test validity of Russian reports and they are consistent with our estimates. Much of this is in our book. Our view is that Russian Battlefield provides a realistic and worthwhile source of data that would otherwise not be available. It is an extremely valuable resource and one which helped improve our book. One has to examine the data closely before using it, which is also the case with Allied information. T34/85's sock it to King Tigers, Wittmann socks it to a column of British vehicles. Doesn't every nation make a big deal out of their aces exploits. If one wants to know how vulnerable T34 and T34/85 were against German panzers, one should look in Jentz. If one takes Russian claims and stories as a source and analyzes them, they are about as accurate and valid as U.S. and British stuff.

Just as the Allies fired all sorts of weapons against the Panther glacis and wrote reports on results, so did the Russians. Funny that no one questions the validity of U.S. and British test reports. What about the U.S. firing tests where 17 pounder and 57mm ATG APDS failed to penetrate or even hit anything, is this American propaganda to dismiss British ammunition? If one trusts one set of penetration tests reports it would be appropriate to give the same treatment to the other until such time as one could disprove the Russian data. Based on the research in our book, Russian tests are as valid as American and British.

Russian Battlefield has several reports where Tiger II's were used on Eastern Front, and they give the number of KT's used by the Germans. All told, it amounts to a substantial percentage of the total when breakdowns on the way to the front are considered. Russian Battlefield penetration ranges during tests at Kubinka and combat reports are also consistent with U.S. tests of 122mm APBC and estimated performance of other Russian ammunition. Considerable support exists to confirm general validity of many, if not all, published Russian penetration ranges. Much of this is covered in our book. [ 06-25-2001: Message edited by: rexford ]

The 1200m penetration range against Tiger I for 122mm AP and APBC hits correlates well with the mantlet resistance on the main areas. The range may be a maximum at which any area on the Tiger front may be penetrated. Calculated penetration ranges against German tanks with Russian data have to be examined very carefully, because the penetration data may be "tabular" results (calculations). This sort of data is listed on the Russian Battlefield site. 122mm APBC is given about 168mm penetration at point blank using "tabular" results, U.S. tests show 207mm at point blank for 122mm APBC and Russian curves on Russian Battlefield show 215mm at point blank. Our research showed that Germans had "tabular" results for Russian penetration, which tend to be DeMarre estimates from 76.2mm against zemented armor and are too low. German estimates of penetration ranges by Russian ammo are also flawed due to special slope effects for Russian APBC ammo, and flaws in Panther glacis armor. Russian APBC would have 1.50 slope effect against Hetzer 60mm at 60° glacis, Germans might use APCBC slope effect of 2.60 in their estimates. WW II calculated penetration ranges are estimates that may really be off the mark. No one was aware during WW II of special ability of Russian APBC to penetrate sloped armor, Germans don't seem to have recognized the difference. And Russians published "tabular" results which seem to have deceived Germans into missing the significance of flat nose projectiles.

Regarding production output, don't forget the armor factories that the U.S. built in Russia prior to the war, which helped produce the first T34's. And the armor plate the U.S. sent over. Jeff Duquette found an article on the above subject.