rexford

Flamingknives made some very good points regarding armor penetration. The DeMarre equation relates penetration to the weight, diameter and velocity of rounds in the following manner: velocity raised to 1.43 power times diameter raised to 1.07143 power time (weight/diameter cubed) raised to 0.7143 power times a constant If 40mm solid AP and 75mm solid AP rounds hit and penetrate an 80mm vertical plate on half the hits, and the weight/diameter cubed ratio is the same for both AP, the 75mm round will penetrate at about half of the velocity needed for 40mm AP to succeed. In terms of energy needed to penetrate the 80mm plate, 40mm AP would require 36% less impact energy than 75mm AP (75mm succeeds at about half the striking velocity of 40mm but weighs almost six times more). 75mm M72 AP penetrates 114mm homogeneous at 2030 fps (619 m/s), 40mm 2 pdr AP penetrates 87mm at 2600 fps (792 m/s). Projectile size counts alot when it comes to penetrating a given thickness of armor, but smaller rounds are better at transferring energy into effectiveness. [ May 01, 2003, 10:17 PM: Message edited by: rexford ]

FACE HARDENED ARMOR Face-hardened armor is abbreviated FHA. The theory as I understand it is that the very hard surface layer, which can vary from 450 to 600 Brinell Hardness on German tanks, causes the nose of uncapped AP to break. The softer plate material behind the face-hardened layer absorbs the energy in the fragments. The existence of the softer ductile material behind the face-hardened layer prevents the kind of situation that exists when a 450 Brinell plate on a T34 (45mm thick) is hit by a 75mm round and loses 24% of its resistance. The combination of a hard thin surface layer and a softer backing assure that 50mm of face-hardened armor resists 45mm and 75mm hits like 50mm of face-hardened armor. Face-hardened armor is best against small rounds, and becomes less effective as the AP diameter increases. 2 pdr AP penetrates 62mm face-hardened and 82mm homogeneous at 100m, for a 1.32 ratio (homogeneous/face-hardened penetration). 17 pdr AP penetrates 200mm homogeneous and 164mm face-hardened at 100m, for a 1.22 ratio. U.S. Cal .30 M2 AP bullets penetrates 19.8mm homogeneous and 12.2mm face-hardened at 0m, for 1 1.63 ratio. I read somewhere that the Germans face-hardened their anti-tank gun shields while the British did not, which resulted in greater effectiveness for German tank machine guns when they confronted ATG. German U-Boats may have used face-hardened conning towers to better resist 20mm cannor fire. Using face-hardened armor on German tanks made alot of sense in Afrika until the Allies starting placing armor piercing caps on the ammo. A Sherman firing 75mm M72 solid shot AP can penetrate 93mm homogeneous and 75mm face-hardened at 500m, while the same gun shooting APCBC-HE penetrates 81mm homogeneous and 95mm face-hardened. The armor piercing cap protects the projectile nose from the face-hardened layer and improves performance against that armor, but also reduces homogeneous penetration. One of the raging controversies concerns the effective resistance of layered face-hardened armor. British tests in Africa resulted in penetration ranges that are associated with 69mm single plate resistance when a 32mm face-hard plate is bolted to 30mm face-hard on Pzkpfw IIIH front hulls. The angle of the tests is not given, could be 0 degrees side angle or could be 30 degrees. If the angle was 30 degrees from firer to hull facing, than the 32mm/30mm FHA combo would be equivalent to a single FHA plate of 57mm thickness. Which would suggest that layered FHA plates resist with less than their total combined thickness. German statements regarding layered FHA armor indicate that two FHA plates in contact offer less resistance than a single FHA plate of same overall thickness, which supports the 57mm result and a 30 degree side angle during the tests. This would impact the resistance of the PzKpfw IVG with 30mm/50mm layered FHA armor on the front hull, and suggest that the 30mm/50mm combo was equivalent to about 76mm single FHA plate resistance. The German use of bolted on 32mm FHA plates atop 30mm FHA created a maintenance problem, as angled hits would bend and shear the bolts. Welding was used but required considerable set-up care. German use of face-hardened armor may have continued after the Allies started to use armor piercing caps because the Russians did not use that sort of cap during the war. This could have convinced the Germans that face-hardening was worth the extra effort and must have increased the armor resistance to Russian rounds compared to homogeneous armor plate. Calculations for 45mm AP and APBC indicate that face-hardened armor would decrease the penetration range that applied to homogeneous armor, although 76.2mm APBC would penetrate more face-hardened armor at all ranges. Panther D and early Panther A had face-hardened side hull armor, which offered some protection against 45mm hits but made the tank more vulnerable to side hits by 76.2mm field guns and T34 tanks. One interesting fact that suggests that the Germans did not appreciate the performance of Russian ammo is the way Russian penetration figures were used in German calculations. The Germans used Russian penetration figures, which are against face-hardened armor, to compute penetration ranges against panzers with homogeneous armor. In the case of 122mm AP, the 166mm face-hardened penetration figure at 0m resulted in the conclusion that IS-2 tanks could not penetrate the glacis of Panther A and G at point blank range. The problem is that the 166mm penetration figure for IS-2 AP is related to 80% success, and converts to 175mm at 50% success. And the homogeneous penetration of 122mm AP would be much greater than the face-hardened figure, where we estimate that 122mm AP could penetrate 201mm of homogeneous armor at point blank. A similar calculation was made for SU 100 AP would have underestimate the ammo performance against Panther tanks. On the battlefield, IS-2 tanks penetrated the Panther glacis at 700m. Miles Krogfus' article in the May-Aug. issue of aFV News allows one to compute Russian penetration against face-hardened armor at 80% success, and multiplying the result by 1.06 converts to 50% success (half the hits completely pierce the armor). Face-hardened armor was used on front of PzKpfw III, PzKpfw IVF1 through IVJ, StuG III, Panther D (glacis and nose, hull side) and early Panther A (nose and hull side). Face-hardening of PzKpfw IV armor ended June 1944. [ May 01, 2003, 09:52 PM: Message edited by: rexford ]

Homogeneous Armor Homogeneous armor is designed for the same hardness all the way through the thickness, but can be medium or high hardness. ABout 375 Brinell Hardness is often used as the boundary between machineable quality armor (machined with normal tools) and the high hardness stuff. PzKpfw II and T34 used high hardness armor that exceeded 400 Brinell Hardness, and the armor performed well when the projectile diameter was smaller than the armor thickness. American tests with U.S. and Russian armor plate showed that when projectiles were wider than the armor was thick, the high hardness stuff was less resistant than medium hardness armor. If T34 glacis were good quality medium hardness RHA (rolled homogeneous armor), 75L43 would be limited to a 500m penetration range. Reports in Jentz' Panzertruppen books indicate a 1000m max penetration range for 75L43 against T34 in one case, and a 1600m max range in another combat where hits at 1200m penetrated regardless of impact angle. Russian tests with 75L43 showed penetrations of T34 glacis at 1000m and 30 degrees side angle, which is consistent with a 24% decrease in resistance relative to medium hardness rolled plate. Cast armor is homogeneous armor but is not rolled, which weakens the structure relative to rolled armor. A 2" casting hit by 75mm APCBC is 13% less resistant than 2" of rolled armor, and a 4" casting would be 5% less resistant, so the armor thickness/projectile diameter ratio is coming into play again. When two medium hardness homogeneous armor plates are placed in contact, such as the Sherman jumbo, the resistance is less than a single plate with the same overall thickness. This result is due to the fact that the resistance of homogeneous plates is less at the surface, where the material isn't constrained from movement as much as the interior (the projectile has an easier time pushing surface material out of the way). When two plates are against each other there's twice the surface area of a single plate. [ May 01, 2003, 06:47 AM: Message edited by: rexford ]

Spaced Armor Germans used spaced armor on PzKpfw III, where 50mm main armor on turret and driver plate had a 20mm spaced plate mounted. The spacing was designed to defeat hits by: 1. detonate HE burster in projectile after penetration of 20mm plate, where face-hardening on 50mm plate would survive fragments 2. dull uncapped AP rounds on 20mm plate which would reduce penetration against face-hardened 50mm 3. remove armor piercing cap from APC and APCBC hits, reducing face-hardened penetration 4. cause rounds to fracture on angled hits as they were suddenly jerked penetrating 20mm plate There may also be some advantages against HEAT rounds. As an aside, HEAT penetration is decreased when the Brinell Hardness of the plate is higher than 240. Russian tests with 122mm ammo showed that 20mm spaced plate and 50mm main armor defeated hits by exploding the round between the plates. British tests with 75mm APCBC showed same result, which lead them to remove HE bursters from round and replace filler with inert material. The down side of spaced plate? The 20mm plate was either 350 or 400 Brinell Hardness, very brittle, and could not take many hits without serious cracking and eventual destruction. A tanker who fought in Africa pointed out to me that many pictures of PzKpfw III that came with spaced armor are missing either the turret or hull spaced plate, or both.

Okay to post anywhere. Good idea. Additional definitions follow: APCR or HVAP Armor Piercing Composite Rigid and Hyper-Velocity Armor Piercing ammo. There are limits on penetration capability of steel projectiles, the noses shatter at high velocity and they weight too much to accelerate to very high velocity. Tungsten is dense and hard, doesn't shatter on really high velocity hits against vertical armor and a small core can be contained in a light weight full diameter carrier that has little overall weight. Problem is that light weight and full diameter leads to higher than normal velocity loss with range. Tungsten rounds also tend to break easily against sloped armor (high hardness comes with low impact resistance), leading to high slope effects. 76mm APCBC hitting 80mm at 55 degrees is resisted by 202mm vertical equivalent, 76mm and 90mm HVAP hitting same armor is resisted by 276mm vertical. Since 76mm HVAP penetrated 208mm at 500m, Panther glacis would be a very difficult target and American 76mm gun with HVAP was definitely not the answer against Panther. Against vertical armor 76mm and 90mm HVAP penetrate 239mm and 306mm at 100m, so rounds are definitely more effective against armor at low slope. Germans and Russians used arrowhead APCR, which had poor aerodynamic shape although cut-out area behind nose saved weight. Germans replaced early arrowhead shape with more conventional and aerodynamic design, Russians stuck with arrowhead which was copied from Germans. "Russians placed a mercury compound in their APCR rounds, which held core to carrier and the compound was vaporized by frictional forces when core penetrated target. Result was a toxic gas released inside the penetrated vehicle, which could sicken and kill crew members (after gas settled vehicle could be re-entered)." Preceding discussion paraphrased from the following reference for 45mm APCR characteristics: http://www.geocities.com/Pentagon/Base/1852/57mm.html#24 Tungsten core diameter is about half gun diameter for U.S. and British rounds, Russian 76.2mm and 85mm cores are just under 28mm width. APDS The somewhat poor aerodynamics of HVAP and APCR can be improved by having the carrier of the core fall away after it leaves the barrel. APDS stands for Armor Piercing Discarding Sabot. British APDS, both 6 and 17 pounder types, often had irregular flight path and unstable trajectory, causing wild errors at all ranges and cases where rounds would bounce off armor they should have easily defeated. Possible cause may have been uneven shedding of the carrier on one side. British tests with 17 pounder APDS showed that it could penetrate Panther glacis at 700 yards when it worked properly. Americans were given 6 pdr APDS rounds which were used with 57mm anti-tank guns, results varied from most effective at hitting and penetrating to couldn't hit a target very much during penetration tests. Squeezebore German 28/20 gun is an example of the Gerlich or squeezebore concept. Tungsten ammo placed in gun is 28mm wide and is squeezed down as it travels barrel to 20mm. Result is a very high velocity round which is small, light and loses velocity relatively quickly. [ April 30, 2003, 11:15 PM: Message edited by: rexford ]

This post is from another thread but is used with a new topic to bring it to the attention of more folks. AP is an armor piercing round that is shaped for penetration effectiveness but has a poor shape in terms of air resistance. AP is good against medium hardness homogeneous armor (same hardness all the way through the plate thickness), but loses velocity and penetration somewhat quickly with range. AP stinks against face-hardened armor, where a thin surface layer is much harder than the steel projectile nose. Face-hardened armor tends to damage the nose of AP rounds, significantly decreasing the penetration capability. APBC is a blunt nose Russian round that penetrates more face-hardened armor than homogeneous at 76.2mm diameter. The APBC is somewhat soft but it has very good impact resistance or toughness. The ballistic windscreen cap on APBC cuts air resistance very nicely. So 76.2mm APBC penetrates face-hardened armor very well by suddenly unloading a tremendous impact on the hard surface layer, and APBC penetrates homogeneous plate by tearing the armor around the outside of the impact area. I've seen pictures of blunt nose ammo penetrating homogeneous plate and it really does tear the armor and pushes a plug of steel out through the plate. Is 76.2mm APBC a really good idea? A T34 firing 76.2mm APBC at 662 m/s can penetrate about 72mm of homogeneous armor and 76mm of face-hardened armor at 500m. A Sherman firing 75mm APCBC at 619 m/s can penetrate 81mm homogeneous and 95mm face-hardened at 500m. APCBC is an armor piercing round with a ballistic windscreen to cut air resistance and an armor piercing cap which absorbs the large impact when rounds hit the hard face-hardened layer. The Sherman round, fired at a lower velocity, is better in many ways. Armor piercing caps are a solid layer of steel that overlays the projectile nose and spreads the impact over a bigger area, and the caps even have an air space over the projectile nose to further protect that sensitive spot. One of the big advantages of APBC over AP is that the flat nose tends to dig into homogeneous armor when it is sloped, which counters the ricochet effect. So APBC is very good against sloped plate. 122mm AP penetrated the Panther glacis at 700m during initial combats, 122mm APBC would penetrate at 1500m due to the flat nose surface and the windscreen that reduces velocity/penetration loss with distance. APBC does not have a total flat nose, the area that is flat ranges from 20% of total diameter on 122mm APBC to 40% on 76.2mm APBC. American tests with flat noses that made up about 80% or more of the diameter showed that those rounds tended to break up against armor thicknesses greater than the projectile diameter.

Sorry for the headache. And the unexplained abbreviations. AP is an armor piercing round that is shaped for penetration effectiveness but has a poor shape in terms of air resistance. AP is good against medium hardness homogeneous armor (same hardness all the way through the plate thickness), but loses velocity and penetration somewhat quickly with range. AP stinks against face-hardened armor, where a thin surface layer is much harder than the steel projectile nose. Face-hardened armor tends to damage the nose of AP rounds, significantly decreasing the penetration capability. APBC is a blunt nose Russian round that penetrates more face-hardened armor than homogeneous at 76.2mm diameter. The APBC is somewhat soft but it has very good impact resistance or toughness. The ballistic windscreen cap on APBC cuts air resistance very nicely. So 76.2mm APBC penetrates face-hardened armor very well by suddenly unloading a tremendous impact on the hard surface layer, and APBC penetrates homogeneous plate by tearing the armor around the outside of the impact area. I've seen pictures of blunt nose ammo penetrating homogeneous plate and it really does tear the armor and pushes a plug of steel out through the plate. Is 76.2mm APBC a really good idea? A T34 firing 76.2mm APBC at 662 m/s can penetrate about 72mm of homogeneous armor and 76mm of face-hardened armor at 500m. A Sherman firing 75mm APCBC at 619 m/s can penetrate 81mm homogeneous and 95mm face-hardened at 500m. APCBC is an armor piercing round with a ballistic windscreen to cut air resistance and an armor piercing cap which absorbs the large impact when rounds hit the hard face-hardened layer. The Sherman round, fired at a lower velocity, is better in many ways. Armor piercing caps are a solid layer of steel that overlays the projectile nose and spreads the impact over a bigger area, and the caps even have an air space over the projectile nose to further protect that sensitive spot. One of the big advantages of APBC over AP is that the flat nose tends to dig into homogeneous armor when it is sloped, which counters the ricochet effect. So APBC is very good against sloped plate. 122mm AP penetrated the Panther glacis at 700m during initial combats, 122mm APBC would penetrate at 1500m due to the flat nose surface. APBC does not have a total flat nose, the area that is flat ranges from 20% of total diameter on 122mm APBC to 40% on 76.2mm APBC. American tests with flat noses that made up about 80% or more of the diameter showed that those rounds tended to break up against armor thicknesses greater than the projectile diameter.

1. It appears that the Germans were unaware of what blunt nose APBC could do against face-hardened armor. The Germans publish and use Russian penetration figures for comparisons against homogeneous armor and never realize it is against face-hardened armor. This is odd, cause a German Intelligence report on SU 85 clearly states that the penetration data is calculated against face-hardened armor, yet other German documents use the same figures for penetration range analysis vs homogeneous armor on Tiger and Panther. The Germans use the face-hardened penetration of 122mm AP to determine that the round cannot penetrate Panther glacis at any range or angle. Try 700m based on combat experience against good quality armor. The Germans appear to have missed the implications of blunt nose APBC. In a similar vein, the British did not realize the Germans were using face-hardened armor till well into 1942, at which point they started to look at armor piercing caps. That's alot of years of PzKpfw III and IV with face-hardened armor before the British wake up. Sometimes one completely misses the boat when it comes to analyzing armor and penetration (did I leave myself vulnerable on that one?). 2. 80mm face-hardened on PzKpfw IV was good at stopping 45mm and 76.2mm APBC and AP, and both fired rounds without armor piercing caps. And it was a "given" at the time that an armor piercing cap was needed to defeat face-hardened armor at good ranges. 3. Based on my calculations 45mm AP penetrates less face-hardened than homogeneous, and the same holds for 76.2mm AP. And 45mm APBC penetrates more homogeneous armor than face-hardened at close range. So face-hardened armor would be better against 45mm rounds, which constituted alot of the Russian anti-gun inventory. ============================================== Interestingly, there is a sentence on the John Salt site, the penetration data document, where 28/20 Gerlich tungsten ammo penetrates 76mm of medium hardness homogeneous armor at 100 yards but almost makes it through 87mm of face-hardened plate. 17 pdr APDS penetrates 231mm of face-hardened armor at 1000 yards and 30 degrees, and penetrates less homogeneous armor at the same angle and range. So tungsten ammo looks better against face-hardened than homogeneous, which makes sense since tungsten rounds are harder than face-hardened armor which reduces the ability of that armor to break up the projectile hit. And once the face-hardened surface fails the armor loses much of its resistance. Russian APCR may have been more effective against face-hardened armor than homogeneous. If the preceding is true, are the published Russian stats for APCR penetration against face-hardened or homogeneous armor? And should they be adjusted for either type of armor?

The interesting thing about the Tiger introduction is that Russian 76.2mm APBC ammo wasn't being designed for thick homogeneous armor at the time that Tiger made its appearance. During late 1942 and early 1943, many of the rounds for 76.2mm guns were the BR-350A blunt headed APBC, which was a 1940 development according to Miles Krogfus' article on the Russian ARTKOM equation (AFV News), and the ammunition penetrated (662 m/s muzzle velocity): BR-350A PENETRATION Range......Homogeneous.......Face-Hardened 50m...........80mm.............83mm 100m..........77mm.............82mm 500m..........68mm.............75mm 1000m.........59mm.............66mm 1500m.........53mm.............59mm Against PzKpfw III and IV, and StuG III, with 30mm or 50mm face-hardened front hull and turret armor, 76.2mm BR-350A was very capable and allowed Russian guns to open fire at 1500m or beyond and stand a great chance of penetrating German frontal armor. According to information provided by John Waters, Russian 76.2mm field gun crews were advised to open fire on StuG III's at 1500m. There have been posts on a variety of forums where claims were made that the main armor on Tiger (102mm and 82mm) was designed to be impervious to Russian 76.2mm hits at all ranges and angles. If the German designers were using BR-350A performance as the key their design seems to have met expectations, since the 82mm and 102mm homogeneous armor was well beyond BR-350A performance. Both BR-350A and the improved BR-350B were tested against Tiger armor during April 1943 tests according to Miles Krogfus, and neither could defeat the 82mm side armor "at an acceptable combat range". BR-350B could penetrate 5% more than BR-350A, which meant that 82mm homogeneous plate could be defeated at about 60m on half the hits if the shot was made along the perpendicular from the armor surface (based on penetration estimates from U.S. tests with 122mm APBC). BR-350A production ended during 1943. Miles' article notes that during late 1943 a percentage of the BR-350B rounds were specially heat treated, and the penetration increase works out to be about 10%. The special BR-350B rounds would penetrate the following thicknesses of homogeneous armor (Tiger armor type): 50m, 92mm 100m, 89mm 250m, 84mm 500m, 79mm 750m, 73mm During late 1943 the 76.2mm guns benefited from better BR-350B rounds and APCR ammo, which closed the penetration gap against Tiger side armor. The early dominance of the battlefield by Tiger tanks can be related to armor plate that was thicker than the design performance of Russian 76.2mm ammo, and the use of unusually hard armor for 62mm, 82mm and 102mm plates which may have added some extra resistance. When the 76.2mm APBC penetration is within a few millimeters of the Tiger side armor thickness, adding a few percentage points due to hard armor could make the difference between penetration and survival. It should also be noted that the British firing tests against a Tiger in Africa found that one of the side plates was poor, which could allow an occasional penetration to occur, although the Brits found most Tiger armor to be good quality. The occasional bad plate may explain some of the penetration ranges that are often noted as being inconsistent with other combat and test results.

rexford, I've been following this thread with some interest, finding it very interesting and informative. The technical knowledge displayed here by several members are far beyond my small abilities with respect to armor combat and gunnery, yet I find it very fascinating, to say the least. Your last post, however, compels me to caution you. These instructions from Voronov who was one of the better Soviet Marshals at the time - and certainly competent - may have been erroneous, but I doubt very much it was propaganda. Consider what this report represented, who was meant to read it and why.</font>

The following report is interesting but it appears to be calculations and propaganda. Penetration ranges are based on calculations using face-hardened penetration figures from ARTKOM equation, which are then incorrectly applied to homogeneous armor on Tiger. 76.2mm AA gun fires BR-350A at 745 m/s and round penetrates 81mm face-hardened at 500m. Russians then determine that 76.2mm AA gun can defeat Tiger side armor at 500m. German reports for Tiger indicate that it could, and did, take all sorts of hits in the wheels and tracks and still moved on its own. Tigers did lead advances, although Tigers did withdraw from artillery. Just like that rubbish report about IS-2 tanks running from Tigers, the Russians put out a propaganda piece of their own on Tiger. Also note, as John Waters pointed out, Russian firing tests against a captured Tiger were not incorporated into the April 20, 1943 instructions since the Kubinka tests were not completed yet.

BR-471 is uncapped 122mm AP, BR-471B is APBC for that gun. Russian Battlefield penetration figures for BR-471 uncapped AP are based on 640 m/s velocity at 2000m, which is nonsense.

The tests show that Tiger 82mm side armor consistently outperformed high quality U.S. and British penetration test plate. 12 of 14 results equal or exceed the resistance of Allied penetration test plates. Firing angles varied from 0 degrees through 55 degrees lateral angle. The variation in penetration resistance appears to be based on the quality of the plate. The 2-of-14 penetration probability estimate was a rough figure because I don't have the time to calculate for an hour this week. It is reasonable to assume that the hardness of early Tiger side armor may have contributed to the defeat of Russian hits.

A Russian "Instruction on Fighting German Tank T-VI", published 20 April 1943 and referenced by John Waters, has penetration range figures for the subject gun against Tiger. It is stated that the 76.2mm AA gun, firing armor piercing rounds, can penetrate the Tiger side armor (hull and turret) and rear at 500m, while the 76.2mm field gun cannot penetrate at any range with the same rounds. It is a fact that the Russians often used their ARTKOM penetration estimates against face-hardened armor to estimate penetration ranges against tanks with homogeneous armor, like Tiger. If the ARTKOM equation in Miles Krogfus' recent AFV News article is used to estimate the 500m penetration for BR-350A APBC fired at 745 m/s, the 500m figure is 81mm. I chose the 6.3 kg BR-350A APBC round because the most common Russian penetration figures for 76.2mm APBC (69mm at 500m, 61mm at 1000m) are based on that round. This suggests that the 745 m/s muzzle velocity that occasionally shows up for 76.2mm Russian guns may be the AA gun. Based on a DeMarre estimate from the U.S. tests with 122mm APBC against medium hardness homogeneous armor, 76.2mm BR-350A fired at 745 m/s would penetrate about 83mm homogeneous at 500m.

Published Russian penetration ranges and trial results against Tiger side armor resulted in some conflicting conclusions, among which was a failure of 76.2mm APBC against the 82mm side plates at 200m (angle not given). American and British firing tests against the high Brinell Hardness 82mm Tiger side plates indicated that in 9 cases out of 14, the armor exceeded the predicted resistance of good quality Allied armor. The excess resistance varied from 1.2% to 13.3%, with firing guns in the 57mm through 90mm range. It is quite possible that the Tiger which was fired upon by the Russians during April 1943 was in the upper half of the expected armor resistance variations. EFFECTIVE RESISTANCE OF 82MM TIGER SIDE PLATES ARMOR HARDNESS IN 313 TO 359 BRINELL RANGE CASE/RESISTANCE RATIO/EFFECTIVE RESISTANCE 1/1.133/93mm 2/1.112/91mm 3/1.077/88mm 4/1.062/87mm 5/1.049/86mm 6/1.049/86mm 7/1.024/84mm 8/1.020/84mm 9/1.012/83mm 10/1.000/82mm 11/1.000/82mm 12/1.000/82mm 13/0.947/78mm 14/0.939/77mm Estimated 200m penetration against medium hardness homogeneous armor for 76.2mm BR-350A and BR-350B APBC is 73mm and 78mm. Estimates derived from U.S. tests with 122mm APBC and 662 m/s muzzle velocity for 76.2mm APBC. Comparing the 76.2mm APBC penetration estimates with the Tiger side armor resistances for early models with very hard plate, the chance that BR-350B will penetrate at 200m is about 2-in-14. It should be noted that we do not have actual Russian penetration test results for 76.2mm APBC against medium hardness rolled armor, so the above figures are estimates. Various armor penetration theories hold that unusually hard armor may have added resistance against projectiles if the armor is able to fracture the projectiles. Damage to projectiles uses the energy of the hit to break apart the projectile, which lessens the impact forces on the hard armor. [ April 27, 2003, 09:32 AM: Message edited by: rexford ]

Gorgias said: " "Artillery was the main weapon of the Red Army. Not all Russian cannon types could penetrate Tiger's armor, but concentrating the fire of all possible guns on the tanks could heavily damage them, even to the point of stopping the engine or detonating the ammunition. The 76.2mm ZIS-3 cannon, using anti-tank shells, could penetrate Tiger side armor (at 300-400 meters) or destroy the running gear, while it couldn't penetrate the frontal armor." Where does the 300-400 meter effective range for 76.2mm APBC against Tiger side armor come from? Very important issue that needs solid references. Russian data for 76.2mm face-hardened penetration is represented by the ARTKOM equation that Miles Krogfus presented in his article. 76.2mm firing 6.5 kg APBC penetrates 86mm face-hardened at point and: 0m 86 100m 84 200m 82 300m 80 400m 78 500m 76 600m 74 Against a single 80mm thick face-hardened plate 76.2mm penetrates on half the hits at 200m, since there is a slight vertical slope. We're not talking about layered 30mm/50mm now, just one 80mm plate. StuG III with 30mm/50mm add-on still had 50mm on mantlet, if I remember correctly. Did it have added 30mm plates for front lower hull? My models don't show added armor on the lower hull front. So front of reinforced StuG III front has weak areas on mantlet (fairly large area close to center of aim, so it gets hit ALOT) and that big lower front hull. Could some check to see if add-on 30mm was added to StuG III lower front hull, it wasn't added to PzKpfw III with 20mm+50mm spaced so I doubt it was added to StuG III nose. Was 30mm added to PzKpfw IVG nose when it was added to driver plate? In every case? The 80mm single plate StuG III probably had 80mm plates on front lower hull, but wasn't the mantlet still 50mm thick? The thing about the ARTKOM equation is that is gives one a single penetration figure, but Miles' article points out that projectile nose hardness and penetration could vary from ammo lot to ammo lot.

The 122mm AP penetration figures are homebrew, based on extrapolation from British and American AP rounds using nose hardness factors.

There's something else about the Russian penetration stats for 122mm AP that should be understood. The velocity estimates versus range are really not very good. Working backwards from penetration data (CP) on Russian Battlefield site, the muzzle and 2000m velocities work out to 780 and 640 m/s (ARTKOM equation in Miles Krogfus article). 122mm AP was actually fired at 792 m/s, and 2000m velocity was about 560 m/s. I have access to a trajectory computer program that estimates velocity versus range, and 122mm AP is not going 640 m/s at 2000m. Input to program was very good drawing of projectile shape.

Russian 122mm AP is an uncapped projectile with very poor ballistic shape (it's kinda blunt), 75L48 APCBC has a special cap that acts as a windscreen and lowers air resistance (streamlined looking). From 0m to 1000m 122mm loses 21% of 0m penetration, 75L48 APCBC also loses 21%. 75L48 APCBC has better aerodynamic shape, 122mm AP has higher mass/diameter ratio (this is velocity staying power, explains why baseball can be thrown further than a hollow whiffle ball of same size as baseball). 122mm AP is also fired at a higher velocity than 75L48 APCBC, 792 m/s against 750 m/s, which helps to retain velocity over range. 75L48 "mass/diameter squared" ratio is 0.001209 122mm "mass/diameter squared" ratio is 0.00168 ratio is kg/millimeters squared Penetration figures for 122mm AP from Russian Battlefield site are against FACE-HARDENED ARMOR. This is what Miles Krogfus' recent article indicated. 122mm AP penetrates about 162mm CP at 0m, 80% of successes, against face-hardened armor. For 50% success, 162mm x 1.06 = 172mm against face-hardened armor. My latest figures for 122mm AP penetration against homogeneous armor are: 197mm at 0m 192mm at 100m 175mm at 500m 156mm at 1000m 139mm at 1500m 123mm at 2000m 110mm at 2500m 098mm at 3000m

The width of a target is actually one of the least important aspects of target size, height is the primary factor. But at close range the primary ingredient is gunner nerves. If the shot misses and the enemy retaliates, the end is near! Lots of shots go to the side of the target, really wide, cause the gunner rushed the shot. But more rounds land short or go over the target due to nerves, cause the gunner incorrectly set the elevation, or just plain forgot how to aim. I read about a Jagdpanther that missed a stationary Sherman at 300m, the shot ended up in the dirt well short of the target. The gunner shot well on the range, forgot everything in combat. Also read about a 75mm Pak 40 that fired APCR at a T34 moving towards it at 100m and the shot missed! Went over the tank. At close range most guns fire fairly flat trajectories and shots go where they are aimed. High and low misses would seem to be the main type of inaccuracy, caused by gunner error.

The 76.2mm BR-350B might have penetrated the Tiger II side armor in a test because they were using the special super round available late 1943, and the armor was inferior. Russian APBC is flat nose and nose hardness is on order of 45-50 Rockwell C, American 75mm M72 AP has a very sharp point and is 54.5 Rockwell C Hardness nose. 75mm M72 will easily outpenetrate 76.2mm BR-350B against vertical homogeneous splate, while 76.2mm will close the gap against thinner armor at a bigger angle. Flat noses kick butt against angled homogeneous armor because the edges dig into the plate and counteract the ricochet forces.

Following are my latest revised penetration figures for 76.2mm firing APBC (BR-350B): Typical Round BR-350B 84mm at 0m homogeneous, 86mm face-hard 80mm at 100m, 84mm face-hard 77mm at 250m, 81mm face-hard 72mm at 500m, 77mm face-hard 67mm at 750m, 72mm face-hard 62mm at 1000m, 67mm face-hard 76.2mm APBC BR-350B penetrates 80mm at 9 degrees slope (PzKpfw IVH driver plate) at just under 250m if armor is face-hardened, based on my interpretation of Miles' article. Special Super Round for BR-350B (available late 1943 according to Krogfus article): Increase above figures by 10% Above estimates based on U.S. tests with 122mm against rolled homogeneous armor, which were converted to 76.2mm APBC effectiveness at 662 m/s muzzle velocity. Face-hardened figures from Miles' article, which presents equation and constants to be used. The ranges posted by John Waters on CMBB forum suggest that 76.2mm BR-350A could not penetrate Tiger side at any range, where BR-350A might be primary round during April 1943 trials against Tiger. BR-350A would penetrate about 8.4% less than BR-350B according to data in Miles' article, so reduce typical pen figures in table above for BR-350A and obtain 750m pen range for 76.2mm BR-350A against 62mm armor on Tiger lower side.

John Waters said: "It's also interesting Soviet M4A2 Sherman tankers reported the 75mm M72 round could reliably defeat the Tiger E side hull & turret armor." 75mm M72 AP can penetrate 93mm of homogeneous armor at 500m, and over 100mm at close range. Russian Battlefield penetration figures are not against armor type carried by Tiger, so cannot be compared. That is what Miles' article indicates. Following are my latest revised penetration figures for 76.2mm firing APBC (BR-350B): Typical Round 84mm at 0m 80mm at 100m 77mm at 250m 72mm at 500m 67mm at 750m 62mm at 1000m Special Super Round for BR-350B (available late 1943 according to Krogfus article): Increase above figures by 10% The ranges posted by John Waters suggest that 76.2mm BR-350A could not penetrate Tiger side at any range, where BR-350A might be primary round during April 1943 trials against Tiger. BR-350A would penetrate about 8.4% less than BR-350B according to data in Miles' article, so reduce typical pen figures in table above for BR-350A and obtain 750m pen range for 76.2mm BR-350A against 62mm armor on Tiger lower side.

The following response to a post by Jason C on the regular CMBB forum brings out some of the great discoveries and conclusions that follow from Miles Krogfus's article in the May-Aug. issue of AFV News , which just came out: Jason C started off the thread by saying: " I thought some might find interesting the following analysis I made of random side angles and their effects on conclusions drawn from tactical anecdotes about penetration possibilities. The anecdote that got me thinking about the problem was about a couple of Tigers that found themselves in the midst of a formation of T-34/76s and were hit around 20 times without being penetrated. Some wanted to conclude from this that the 80mm flat side armor of the Tiger I was not penetrable by the 76mm at any range. Over at the Russian battlefield site, meanwhile, they list the initial penetration of the BR-350B (capped) round as 84mm at 500m. Of course we do not know whether the capped rounds were available in the engagement in question. But assume it was." Miles Krogfus' article on Russian penetration figures is now available in the May-Aug. issue of AFV News, and is a "must have" for armor penetration fiends. According to Miles, Russian penetration data for 76.2mm BR-350B ammo is against high hardness armor, which I believe to be face-hardened, and is further reduced in general applicability by one other fact that Miles brings out in his article. Miles' article indicates that the Russians produced two qualities of 76.2mm APBC ammo, the general type being mass produced in quantity and a special high potency round which was available but in smaller lots. The published penetration data on the Russian Battlefield site agrees fairly well with the predicted performance of the high potency Russian 76.2mm APBC, and would not apply to the typical ammo used by that gun. One cannot apply Russian Battlefield penetration figures directly to Tiger armor cause the estimates are against an entirely different type of armor. The existence of two BR-350B rounds with differing quality may also explain why 76.2mm hits defeated Tiger II side armor in one test at 300m, and failed miserably in another. =========================================== Starting from U.S. tests with 122mm APBC vs rolled medium hardness homogeneous armor and working to an estimate for BR-350B average ammo at 500m with 662 m/s muzzle velocity, we obtained 72mm penetration at 500m against homogeneous armor plate for BR-350B fired from 76.2mm. So at 500m it is doubtful that T34/76's or 76.2mm field guns firing typical BR-350B will defeat Tiger homogeneous side armor with medium hardness. We estimate 77mm penetration against medium hardness homogeneous armor for 76.2mm typical ammo at 250m. The souped up BR-350B can penetrate Tiger side armor at 500m with a lucky roll and little side angle. Miles' article indicates that Russian tests against Tiger showed that 76.2mm penetrations could not be obtained at reasonable ranges. However, based on my calculations penetration estimates for the relatively rare 76.2mm solid shot AP indicate that that round could defeat 82mm at a good range. Get Miles' article and it will shed some real light on what those Russian penetration figures mean. There is much more in the article than the above discussion addresses.

Jason C started off the thread by saying: " I thought some might find interesting the following analysis I made of random side angles and their effects on conclusions drawn from tactical anecdotes about penetration possibilities. The anecdote that got me thinking about the problem was about a couple of Tigers that found themselves in the midst of a formation of T-34/76s and were hit around 20 times without being penetrated. Some wanted to conclude from this that the 80mm flat side armor of the Tiger I was not penetrable by the 76mm at any range. Over at the Russian battlefield site, meanwhile, they list the initial penetration of the BR-350B (capped) round as 84mm at 500m. Of course we do not know whether the capped rounds were available in the engagement in question. But assume it was." Miles Krogfus' article on Russian penetration figures is now available in the May-Aug. issue of AFV News, and is a "must have" for armor penetration fiends. According to Miles, Russian penetration data for 76.2mm BR-350B ammo is against high hardness armor, which I believe to be face-hardened, and is further reduced in general applicability by one other fact that Miles brings out in his article. The article states that the Russians produced two qualities of 76.2mm APBC ammo, the general type being mass produced in quantity and a special high potency round which was available but in smaller lots. The published penetration data on the Russian Battlefield site agrees fairly well with the predicted performance of the high potency Russian 76.2mm APBC, and would not apply to the typical ammo used by that gun. One cannot apply Russian Battlefield penetration figures directly to Tiger armor cause the estimates are against an entirely different type of armor. Starting from U.S. tests with 122mm APBC and working to an estimate for BR-350B average ammo at 500m with 662 m/s muzzle velocity, we obtained 72mm penetration at 500m against homogeneous armor plate. And 77mm penetration at 250m. So at 500m it is doubtful that T34/76 typical BR-350B will defeat Tiger side armor. The souped up BR-350B can penetrate Tiger side armor at 500m with a lucky roll and little side angle. Miles' article indicates that Russian tests against Tiger showed that 76.2mm penetrations could not be obtained at reasonable ranges. However, based on my calculations, penetration estimates for the relatively rare 76.2mm solid shot AP indicate that that round could defeat 82mm at a good range. Get Miles' article and it will shed some real light on what those figures mean. There is alot more in the article than has been touched on here. [ April 21, 2003, 06:32 PM: Message edited by: rexford ]