rexford

Some time ago Jeff Duquette shared a graph with me that provided penetration figures for 17 pdr APCBC at angles from 0 to 70 degrees, with extrapolation to 75 degrees (rolled homogeneous armor). The vertical penetration is a bit higher than we estimate, 187mm vs 177mm at 0m. The British penetration figures were presented to 600, 1000 and 1500 yards and we extrapolated the data to 0m and 2900 fps impact velocity. The following analysis compares the slope effects for the British data at 0m with the estimates generated by our equation for U.S. APCBC slope effect: 0 degrees, 187mm penetration, 1.00 slope effect 20 degrees, 173mm penetration, 1.08 actual and 1.11 predicted slope effect 30 degrees, 150mm penetration, 1.25 actual and 1.29 predicted 40 degrees, 115mm penetration, 1.63 actual and 1.59 predicted 45 degrees, 101mm penetration, 1.85 actual and 1.82 predicted 50 degrees, 88mm penetration, 2.13 actual and 2.12 predicted 55 degrees, 77mm penetration, 2.43 actual and 2.51 predicted 60 degrees, 66mm penetration, 2.83 actual and 2.97 predicted 65 degrees, 56mm penetration, 3.34 actual and 3.36 predicted 70 degrees, 50mm penetration, 3.74 actual and 4.41 predicted ============================================= Extrapolated penetration data at angle: 75 degrees, 38mm penetration, 4.92 actual and 5.22 predicted The 17 pdr APCBC slope effects follow the U.S. curve fairly closely except at 70 degrees. 17 pdr APCBC penetration at 55 degrees and 0m set at 77mm from British curves, compared to 82mm on curve in test report for German 75mm and 88mm APCBC at oblique angles. In the absence of a low probability success (or hits on weld line, machine gun port, previous hit gouge, etc.), 17 pdr APCBC will not penetrate Panther glacis at any range on level ground. Our analysis of flaw effect for Panther glacis versus 17 pdr APCBC indicates a 0.95 multiplier, which improves British gun performance a little but still results in low success probability.

The British report indicates that at 45 and 55 degrees impact, none of the German rounds penetrated in a condition where the HE burster would work. So, at high angles the German HE filled ammo was just like a solid shot except for the loss of penetration and added work that the HE filler entailed.

Some time ago Jeff Duquette shared a graph with me that provided penetration figures for 17 pdr APCBC at angles from 0 to 70 degrees, with extrapolation to 75 degrees (rolled homogeneous armor). The vertical penetration is a bit higher than we estimate, 187mm vs 177mm at 0m. The British penetration figures were presented to 600, 1000 and 1500 yards and we extrapolated the data to 0m and 2900 fps impact velocity. The following analysis compares the slope effects for the British data at 0m with the estimates generated by our equation for U.S. APCBC slope effect: 0 degrees, 187mm penetration, 1.00 slope effect 20 degrees, 173mm penetration, 1.08 actual and 1.11 predicted slope effect 30 degrees, 150mm penetration, 1.25 actual and 1.29 predicted 40 degrees, 115mm penetration, 1.63 actual and 1.59 predicted 45 degrees, 101mm penetration, 1.85 actual and 1.82 predicted 50 degrees, 88mm penetration, 2.13 actual and 2.12 predicted 55 degrees, 77mm penetration, 2.43 actual and 2.51 predicted 60 degrees, 66mm penetration, 2.83 actual and 2.97 predicted 65 degrees, 56mm penetration, 3.34 actual and 3.36 predicted 70 degrees, 50mm penetration, 3.74 actual and 4.41 predicted ============================================= Extrapolated penetration data at angle: 75 degrees, 38mm penetration, 4.92 actual and 5.22 predicted The 17 pdr APCBC slope effects follow the U.S. curve fairly closely except at 70 degrees. 17 pdr APCBC penetration at 55 degrees and 0m set at 77mm from British curves, compared to 82mm on curve in test report for German 75mm and 88mm APCBC at oblique angles. In the absence of a low probability success (or hits on weld line, machine gun port, previous hit gouge, etc.), 17 pdr APCBC will not penetrate Panther glacis at any range on level ground. Our analysis of flaw effect for Panther glacis versus 17 pdr APCBC indicates a 0.95 multiplier, which improves British gun performance a little but still results in low success probability.

The following notes provide some additional details on the subject firing tests: 1. report is held by the British Public Records Office (PRO) 2. U.S. armor slope curves are based on an analysis of slope effect vs impact angle and T/D ratio (plate thickness/projectile diameter) 3. Projectile weights and HE burster capacity is as follows: 88mm large capacity APCBC: 9.6 kg and 1.65% of weight is HE filling 88mm small capacity APCBC: 10.1 kg and 0.65% of weight is HE filling 75mm very small capacity APCBC: 6.8 kg and 0.20% of weight is HE filling Report indicates that large capacity 88mm ammo is used by Flak 36 and Tiger guns, whereas small capacity is fired by Tiger II and Pak 43. Other references have Tiger I firing small capacity 88mm rounds (German ballistic tables list 88L56 APCBC at 10 kg weight, with 10.2 kg for 88L71 APCBC). 4. 88mm projectiles are single piece monobloc (the main projectile body) whereas 75mm APCBC is two piece with a welded on nose. 5. U.S. firing tests with welded nose projectiles indicated that the round was superior to monobloc rounds at high impact angle, since the nose would break off and allow the ammunition to penetrate intact (single piece rounds would suffer much nose damage, increasing the limit velocity above the two piece rounds). However, past discussions on welded nose German APCBC indicated that 75mm APCBC two-piece shells were heat treated in such a manner that the welded nose did not result in superior performance at high angle (Jeff Duquette contributed the welded nose info if I am not mistaken). The British firing tests with 88mm and 75mm APCBC suggest that German welded nose ammo had about the same sloped armor performance as one piece projectiles would have.

The following notes provide some additional details on the subject firing tests: 1. report is held by the British Public Records Office (PRO) 2. U.S. armor slope curves are based on an analysis of slope effect vs impact angle and T/D ratio (plate thickness/projectile diameter) 3. Projectile weights and HE burster capacity is as follows: 88mm large capacity APCBC: 9.6 kg and 1.65% of weight is HE filling 88mm small capacity APCBC: 10.1 kg and 0.65% of weight is HE filling 75mm very small capacity APCBC: 6.8 kg and 0.20% of weight is HE filling Report indicates that large capacity 88mm ammo is used by Flak 36 and Tiger guns, whereas small capacity is fired by Tiger II and Pak 43. Other references have Tiger I firing small capacity 88mm rounds (German ballistic tables list 88L56 APCBC at 10 kg weight, with 10.2 kg for 88L71 APCBC). 4. 88mm projectiles are single piece monobloc (the main projectile body) whereas 75mm APCBC is two piece with a welded on nose. 5. U.S. firing tests with welded nose projectiles indicated that the round was superior to monobloc rounds at high impact angle, since the nose would break off and allow the ammunition to penetrate intact (single piece rounds would suffer much nose damage, increasing the limit velocity above the two piece rounds). However, past discussions on welded nose German APCBC indicated that 75mm APCBC two-piece shells were heat treated in such a manner that the welded nose did not result in superior performance at high angle (Jeff Duquette contributed the welded nose info if I am not mistaken). The British firing tests with 88mm and 75mm APCBC suggest that German welded nose ammo had about the same sloped armor performance as one piece projectiles would have.

The British report on "German 75mm and 88mm APCBC Ammunition at Oblique Angle", Department of Tank Design Report No. M.6914A/4 No.1 provides test data at 45 and 55 degrees from vertical. Converting the data to performance against vertical armor provides some interesting insights into relative effectiveness. A graph in the report presents the following penetration figures for 88mm APCBC, which are then converted to performance at the Tiger and Tiger II muzzle velocities (2558 and 3280 fps) against vertical plate using U.S. slope effect curves and the DeMarre equation: ========================= 88mm Large HE Capacity APCBC 65mm at 55 degrees & 2750 fps => 135mm at vertical and 2558 fps 58mm at 55 degrees & 2310 fps => 150mm at vertical and 2558 fps 62mm at 45 degrees & 2060 fps => 139mm at vertical and 2558 fps Average = 141mm vertical at 2558 fps ========================= 88mm Small HE Capacity APCBC 81mm at 55 degrees & 2965 fps => 160mm at vertical and 2558 fps 76mm at 55 degrees & 2887 fps => 154mm at vertical and 2558 fps 57mm at 55 degrees & 2220 fps => 156mm at vertical and 2558 fps Average = 157mm vertical at 2558 fps ========================= Note that the small capacity 88mm round outpenetrates the large capacity ammo by about 11%. Following converts small capacity data to 3280 fps muzzle velocity of 88L71 gun: ========================= 88mm Small HE Capacity APCBC 81mm at 55 degrees & 2965 fps => 228mm at vertical and 3280 fps 76mm at 55 degrees & 2887 fps => 220mm at vertical and 3280 fps 57mm at 55 degrees & 2220 fps => 223mm at vertical and 3280 fps Average = 224mm vertical at 3280 fps ========================= Curves are presented for 17 pdr APCBC penetration vs velocity against 45 and 55 degree plate (2900 fps is muzzle velocity of gun firing APCBC): =================== 17 pdr APCBC Solid Shot 82mm at 55 degrees and 2900 fps => 209mm at vertical and 2900 fps 100mm at 45 degrees and 2850 fps => 182mm at vertical and 2900 fps =================== Notable that 17 pdr APCBC is not going to pierce the Panther glacis on other than an occasional hit at 100m and beyond, if hits take place on level ground and do not strike highly vulnerable spots (weld lines, MG mount and ball, driver visor area). The penetration data at 55 degrees results in a vertical estimate which appears to be high, while the 45 degree figure is in line with published figures against vertical armor. 17 pdr APCBC appears to outpenetrate large capacity 88mm APCBC at 45 and 55 degrees by a considerable amount, which may be due to the following combination of factors: 1. solid shot vs HE burster yields greater penetration at all angles 2. British claim 17 pdr APCBC projectile nose is harder, increasing penetration Data is also presented for German 75mm very small HE capacity APCBC: ============================= 75mm Very Small HE Capacity APCBC 58mm at 55 degrees and 2440 fps => 138mm at vertical & 2460 fps 62mm at 45 degrees and less than 2099 fps => above 130mm at vertical & 2460 fps ============================= The vertical penetration estimates for 75L48 APCBC at 2460 fps are consistent with the figures developed using the German equations presented in the BIOS report, while the penetration figures for small capacity 88mm APCBC are lower than the BIOS material predicts. Jeff Duquette deserves much credit for finding the abovenoted British report and pointing others toward the valuable work.

The British report on "German 75mm and 88mm APCBC Ammunition at Oblique Angle", Department of Tank Design Report No. M.6914A/4 No.1 provides test data at 45 and 55 degrees from vertical. Converting the data to performance against vertical armor provides some interesting insights into relative effectiveness. A graph in the report presents the following penetration figures for 88mm APCBC, which are then converted to performance at the Tiger and Tiger II muzzle velocities (2558 and 3280 fps) against vertical plate using U.S. slope effect curves and the DeMarre equation: ========================= 88mm Large HE Capacity APCBC 65mm at 55 degrees & 2750 fps => 135mm at vertical and 2558 fps 58mm at 55 degrees & 2310 fps => 150mm at vertical and 2558 fps 62mm at 45 degrees & 2060 fps => 139mm at vertical and 2558 fps Average = 141mm vertical at 2558 fps ========================= 88mm Small HE Capacity APCBC 81mm at 55 degrees & 2965 fps => 160mm at vertical and 2558 fps 76mm at 55 degrees & 2887 fps => 154mm at vertical and 2558 fps 57mm at 55 degrees & 2220 fps => 156mm at vertical and 2558 fps Average = 157mm vertical at 2558 fps ========================= Note that the small capacity 88mm round outpenetrates the large capacity ammo by about 11%. Following converts small capacity data to 3280 fps muzzle velocity of 88L71 gun: ========================= 88mm Small HE Capacity APCBC 81mm at 55 degrees & 2965 fps => 228mm at vertical and 3280 fps 76mm at 55 degrees & 2887 fps => 220mm at vertical and 3280 fps 57mm at 55 degrees & 2220 fps => 223mm at vertical and 3280 fps Average = 224mm vertical at 3280 fps ========================= Curves are presented for 17 pdr APCBC penetration vs velocity against 45 and 55 degree plate (2900 fps is muzzle velocity of gun firing APCBC): =================== 17 pdr APCBC Solid Shot 82mm at 55 degrees and 2900 fps => 209mm at vertical and 2900 fps 100mm at 45 degrees and 2850 fps => 182mm at vertical and 2900 fps =================== Notable that 17 pdr APCBC is not going to pierce the Panther glacis on other than an occasional hit at 100m and beyond, if hits take place on level ground and do not strike highly vulnerable spots (weld lines, MG mount and ball, driver visor area). The penetration data at 55 degrees results in a vertical estimate which appears to be high, while the 45 degree figure is in line with published figures against vertical armor. 17 pdr APCBC appears to outpenetrate large capacity 88mm APCBC at 45 and 55 degrees by a considerable amount, which may be due to the following combination of factors: 1. solid shot vs HE burster yields greater penetration at all angles 2. British claim 17 pdr APCBC projectile nose is harder, increasing penetration Data is also presented for German 75mm very small HE capacity APCBC: ============================= 75mm Very Small HE Capacity APCBC 58mm at 55 degrees and 2440 fps => 138mm at vertical & 2460 fps 62mm at 45 degrees and less than 2099 fps => above 130mm at vertical & 2460 fps ============================= The vertical penetration estimates for 75L48 APCBC at 2460 fps are consistent with the figures developed using the German equations presented in the BIOS report, while the penetration figures for small capacity 88mm APCBC are lower than the BIOS material predicts. Jeff Duquette deserves much credit for finding the abovenoted British report and pointing others toward the valuable work.

Miles Krogfus sent me a U.S. firing test report which indicates that 37mm, 57mm and 75mm APCBC will all fail against the 30mm/50mm frontal armor on PzKpfw IV at 25 degrees side (horizontal) angle. The shots were taken against the strongest armor on the front of the tank at 0, 30 and 45 degrees, and the 25 degree penetration range was interpolated according to the report. A 25 degree side angle works out to a compound angle of 28.4 degrees from armor perpendicular against the front lower hull (nose), and 26.8 degrees against the driver plate. Interpolating between the curves in TM9-1907 for face-hardened penetration at point blank: 37mm APCBC fired at 2900 fps 61mm at 28.4 degrees and 62mm at 26.8 degrees 57mm APCBC fired at 2700 fps 81mm at 28.4 degrees and 83mm at 26.8 degrees 75mm APCBC fired at 2030 fps 81mm at 28.4 degrees and 85mm at 26.8 degrees The report states that 75mm APCBC fired from the M4 aircraft gun could penetrate the PzKpfw IV frontal armor. TM9-1907 shows a 2380 fps muzzle velocity for 75mm M61 fired from an aircraft, with a point blank penetration of 98mm FHA at 28.6 degrees. The above data suggests that 30mm/50mm layered face-hardened armor resists like a single FHA plate of 81mm+ thickness. While two rolled homogeneous plates in contact resist like a single RHA plate of less total thickness, the U.S. firing results appear to support the British test results against PzKpfw IIIH frontal armor: two FHA plates in contact resist with a single plate thickness greater than the combined two plate thickness. Paul Lakowski has theorized on the Yahoo! Tankers site that two Face-hardened plates in contact may contain an air space between the surfaces, which could radically decrease the projectile performance. It is also possible that layered Face-hardened plates present a greater effective thickness of face-hardened surface armor to be defeated. This issue is far from resolved, since the American analysis of penetration ranges was based on the highest limit velocity, or the shortest penetration range. This approach was taken to estimate weapon effectiveness against the best German armor. It is possible that the average effective resistance could be 7% to 10% less. [ August 21, 2003, 04:47 PM: Message edited by: rexford ]

Really nice Leibstandarte Tigers to blow away British Cromwells, Shermans and Bren Carriers! How come no 007 on the turret side, so one could have a tank force with Wittmann in every tank? Thanks for a great mod!. [ August 17, 2003, 04:24 PM: Message edited by: rexford ]

Really great stuff! The directions on loading the mod were easy to follow, and now my Tiger cannon fodder T34's look so much better. Thanks!!

Looking at the StuG IIIG frontal armor, there is a big difference between the add-on armor areas on PzKpfw IIIH and a StuG. The bolted on armor plates that adorn the StuG III upper front are small in size, and the driver visor cuts out alot of the add-on plate area. Edge effects and possible absence of face-hardening around the edges would impact the StuG add-ons. The 30mm/50mm add-on areas are also small in comparison to the 30mm at 68 degrees from vertical armor plates that make up the front upper superstructure. When 76.2mm APBC hits 30mm face-hardened at 68 degrees from vertical, the effective resistance could be about 75mm vertical. And when that round hits the small add-on areas the resistance could be about 75mm vertical after all of the edge effects are factored in. My inclination is that firing tests against the front of a PzKpfw IIIH would not apply to StuG III with add-on bolted plates. I would agree with Jason C's feeling that StuG III add-on armor areas may be overrated in CMBB, but am not sure about PzKpfw IIIH and IVG/H. ================================================= When two face-hardened plates are put together, the effective resistance should be greater than the sum of the thicknesses. Face-hardened armor works by damaging the projectile nose, which decreases the ammo's ability to make it through the softer plate area that backs the hard surface layer. With two layered face-hardened plates, the first plate does some damage to the projectile nose and the round gets through but with reduced effectiveness against face-hard plate. After the first face-hard plate it meets another face-hard plate, so twice the damage potential. But it is far from clear that the above theory has any validity.

Jason, The comments on the 500m penetration range for Russian 76.2mm against StuG III frontal armor got me thinking that maybe you are on to something. Do you have access to any combat reports or firing tests where Sherman 75mm gun was matched up against the front of StuG III's with add-on frontal armor? This is what I'am trying to sort through: StuG III with 30mm/50mm on driver plate and nose would be compared to 75mm face-hardened penetration of 76.2mm BR-350B at 500m. Driver plate 80mm at 11 degrees is 82mm vertical, nose 80mm at 20 degrees is about 88mm vertical. So Russian 76.2mm APBC is not going to do too well against 30/50 if 1:1 equivalency is assumed. However, if we assume British firing tests against PzKPfw IIIH in Cairo, which resulted in 32mm/30mm being equal to 71mm single plate, were at 30 degrees side angle, 32/30 converts to 56mm single plate. 56/(32+30)= 90% equivalency. So take StuG III 30/50 and convert to single plate equivalency using 90% factor and obtain 72mm single plate. 72mm at 11 degrees is about 74mm vertical 72mm at 20 degrees is about 79mm vertical So, assuming two face-hardened plates in contact act like a single plate with 90% of the total thickness matches the Russian 76.2mm range better than assuming 115% equivalency. Could you re-post the penetration ranges for 25 pdr AP against the front of PzKpfw III's in Africa? With a little more work we may be able to get to the heart of this stuff and make a better assumption. [ August 10, 2003, 08:03 PM: Message edited by: rexford ]

Following statement from http://www.battlefield.ru/is2_1.html "After installing the 122 mm weapon, the turret became very unbalanced. The Design Requirements intended for an increase of its frontal armour thickness to 130 mm which would have unbalanced the turret even further and would have made a new traverse mechanism necessary. SInce all these changes required a complete redesign of the turret, they were all cancelled." The above statement from the Russian Battlefield site appears to rule out design changes (other than the wider mantlet) to the IS-2 turret shape and thicknesses between the IS-2 early and late war models. Which would have maintained the same turret unbalance throughout the WW II life of IS-2 tanks, unless giant weights were hung in the turret rear, which would have required a new turret traverse mechanism (which was not installed). [ August 09, 2003, 11:04 AM: Message edited by: rexford ]

The following will show that the IS-2 turret was always unbalanced by the 122mm gun throughout the war, which placed limits on the thickness of the turret front and mantlet armor. First off, the M10 provides some interesting insights into turret balance. The 3" gun unbalanced the turret, so weights were added to the rear turret overhang. Unbalance in the front is remedied by adding weight to the rear, which makes sense and is consistent with the physics of the situation. Too much on one side requires that more be added to the other side. The IS-1 turret was designed for the 85mm gun, and was balanced. The IS-1 turret armor is 100mm on the sides and rear. The early IS-2 turret became unbalanced because the weight of the 122mm gun put too much weight up front compared to the rest of the turret. The early IS-2 turret had 100mm side and rear armor, same as the IS-1. Now, all of the materials I have reviewed regarding the layout of the late model IS-2 turret show 100mm side and rear armor on the turret, same as the early IS-2. So, if the early model IS-2 turret was unbalanced, so was the late model IS-2 turret. And if the mantlet thickness on the late model IS-2 was increased above the early IS-2, it would add to the unbalance by throwing even more weight towards the turret front (the mantlet weight is shifted towards the front of the turret through the connections). To all of the above I would add that the Russian Battlefield site states that a 130mm turret front armor was ruled out because it would require a new turret traverse to rotate the heavier turret. Well, if 30mm more turret front armor could not be added because it would overstress the traverse mechanism, that would appear to rule out the following: 1. no way the mantlet weight could be increased by a significant amount (like a 60mm increase to 160mm) 2. no way that weights could be placed in the rear of the IS-2 turret to counter the weight of the gun and bring the turret back into balance (have never seen or heard of weight being added to the turret rear of that tank) 3. no way that the turret side and rear armor could be increased by enough to counter the unbalancing created by the 122mm gun In summary, there are MANY facts and statements that totally rule out the theory that the IS-2 turret suddenly became balanced, allowing the mantlet to be thickened substantially. It would be good if evidence could be presented that disputes the above analysis. A brief summary of the facts that support balancing of the turret, and a thicker mantlet, would help here. [ August 09, 2003, 10:47 AM: Message edited by: rexford ]

Yes and no; it all depends on where the weight of the gun is balanced. The weight of the mantlet is not carried by the front of the turret in the same manner as the turret armor itself, rather the mantlet's weight is genrally balaced as part of the gun with which it moves. </font>

You say the drawings are the same as those you found in other Russian references which you have used during your research. Well, the drawings show the thicknesses on the turret front and mantlet remaining the same from IS-1 to IS-2 model 1944. Unless the mantlet numbers (thickness) presented in the books are different, I would say that the reference books disprove the mantlet thickening theory.

Now here's a bit that might explain references to more than 110mm for IS-2 Model 1944 mantlet thickness. Page 34 in our book shows a detailed drawing of the Panther G mantlet, with a cross section. While the nominal thickness is 100mm, the trunnion pad area is 125mm to 135mm thick and the area at the left and right edges is 90mm. So 160mm may be a relatively small and ballistically inconsequential trunnion pad area, while the vast majority of the area is 110mm.

If one compares the IS-1 and late model IS-2 armor drawings on the Russian Battlefield site (see last figures on page at http://www.battlefield.ru/is2_1.html), the IS-1 and late model IS-2 have the same turret front and mantlet thicknesses. The lower hull side thicknesses are also 90mm for both IS-1 and IS-2, which contradicts the statement that the lower hull side armor was increased for late model IS-2 tanks. But the side superstructure thickness in the last drawings is 90mm on IS-1 and 100mm on IS-2, so the Russian Battlefield article on IS tank development is referring to the wrong armor area! Another case where the drawings conflict with the text. [ August 09, 2003, 03:40 AM: Message edited by: rexford ]

It is interesting, and a good observation. Here are the Russian Battlefield statements that form the basis for mantlet strengthening: "As for the tank's turret, it turned out to be impossible to increase its armour protection. Designed for the 85 mm gun, it was completely balanced. After installing the 122 mm weapon, the turret became very unbalanced. The Design Requirements intended for an increase of its frontal armour thickness to 130 mm which would have unbalanced the turret even further and would have made a new traverse mechanism necessary. SInce all these changes required a complete redesign of the turret, they were all cancelled." Increasing the turret front to 130mm is not feasible due to weight problems and turret unbalancing. It looks like the turret weight was not increased, which means that the unbalance problem was not solved. "Nevertheless, the appearance of the turret was considerably changed in the process of its production. The first batch of tanks manufactured in 1943 had a narrow porthole through which the sighting telescope fits. After the installation of the D-25T Main Gun, it became almost impossible to use the telescopic sight, even though its breech was the same as that of the D-5T." Yes, the turret would appear different with a 122mm gun and the widened mantlet. "Starting in May of 1944, a new turret with a widened porthole was manufactured, which resulted in the sight being moved to the left. The armour protection of the tank's mantlet was improved and the armour thickness of the sides of the lower hull was increased." Have not been able to find any data that confirms the statement about the thicker lower hull side, it looks like 90mm on all IS-2 tanks. Now here's the greater contradiction: the turret front armor could not be increased because the added weight would be a problem, but the widened mantlet, which covers a fairly large area compared to the turret front, could have thicker armor and weigh more. One can't have it both ways: if the turret front armor cannot be increased in weight the mantlet also can't increased. However, and this may be the key, a wider mantlet would offer better penetration resistance since edge effects would be reduced. With the narrow mantlet many hits are going to be close to the edge where ballistic resistance is compromised and reduced. With the wider mantlet, most mantlet hits will be far enough from the mantlet edge to have minimal or no reduction in armor resistance. So widening the mantlet improves the resistance to hits even if the thickness remains the same. That may be the meaning of the mantlet armor improvement statement. [ August 09, 2003, 03:44 AM: Message edited by: rexford ]

How many books list 100mm for the Tiger E mantlet? The 100mm is actually the top and bottom edges and the other areas go up to 140mm to 150mm in many areas and over 190mm in a few isolated areas. So if a book stated 190mm maximum mantlet armor it would be as irrelevant as if it said 100mm although 190mm would be correct for the max. Books are wrong alot, even heavyweight ones. My personal opinion is that the IS-1 and IS-2 mantlet was 100mm thick on all WW II models, and the 110mm came from the slight protrusion at the apex that shows up on some photo's. All of the drawings and photo's I've seen suggest that the IS-1 and IS-2 mantlet was rounded and did not have a flattened out area at the apex (except for a slight rectangular protrusion). I see no indication that the IS-2 turret was redesigned to eliminate the unbalanced weight distribution that Russian Battlefield says kept the armor protection the same on IS-1 and IS-2. If the turret was redesigned to do away with the bad center of gravity, then it would have to add armor thickness to the sides and rear of the turret. Provide evidence that early and late IS-2 turret side/rear armor was significantly increased in thickness if it is so clear that the center of gravity problem was resolved. ;o) Adding or rearranging armor on the mantlet is not going to improve things with regard to turret weight balance, the gun is the big sticking point. British data shows the same mantlet/turret armor thicknesses on IS-1, early IS-2 and late IS-2. I believer that Zaloga's 160mm thickness for the mantlet is not correct if it refers to the typical thickness that a shot would land on. The Russians improved the glacis armor because the 30 degree from vertical 120mm thick plate on the IS-1 and IS-2 was getting blown open by Panthers and Tigers and 88L71 ATG. So they put the armor at 60 degrees from vertical which stopped everything at all ranges, HOWEVER: 1. despite the nearly inpenetratable glacis plate, the nose armor was kept at 100mm/30 degrees (Russian Battlefield suggests weight limits eliminated chance of increasing nose thickness or slope), and Russian Battlefield says 100mm/30 deg on the nose was considered okay because few hits struck the nose (which is contradicted by the Russian Battlefield article on IS-2 in action combat, where plenty of tanks were penetrated via the front nose armor). 2. glacis was widened to improve gunsight visibility but thickness was kept the same since turret weight unbalance was problem, there may have been a slight improvement in turret protection since 110mm mantlet covered areas that were previously protected by 100mm turret front So the Russians improved IS-2 glacis but nose and mantlet/turret front armor stayed the same. I think that the Russian Battlefield statement on an armor improvement to the turret is being stretched beyond the breaking point in trying to justify increased mantlet thickness. No relationship has been proposed between more mantlet armor and a solution to the turret weight unbalance problem. I'am an engineer and don't see any numbers that support a solution to the turret unbalance problem which would allow the mantlet to be thickened. Weight appears to have kept the nose thickness down to previous levels on all IS-2 tanks (100mm), and weight limits appear to have constrained the turret front/mantlet armor as well (100mm to 110mm). [ August 08, 2003, 12:33 PM: Message edited by: rexford ]

U.S. firing trials against three Tigers at Aberdeen Proving Grounds showed that 82mm side plates resisted a little better than 82mm of good quality Allied armor. Firing tests against Tiger with 17 pdr APCBC are presented in Thomas Jentz' Germany's Tiger Tanks, Tiger I and II: Combat Tactics; 82mm plates hit at 50 degrees ============================= no penetration when 17 pdr penetration is 76mm/50 deg. shot lodges when 17 pdr penetration is 82mm/50 deg. no penetration when 17 pdr penetration is 87mm/50 deg. ============================= 102mm plate hit at 10 degrees ============================= shot lodges when 17 pdr penetration is 98mm/10 deg. A shot lodges when the penetration is a small amount below the 50% defeat limit, so the above tests with 17 pdr APCBC suggest that Tiger front and side armor was about equal to British quality plate. British statement in WO report collected by John Salt indicates that Tiger armor is good quality except for an occasional bad plate. Following test results for 82mm side plate at Aberdeen: plate resists 76mm APCBC hit at 0 deg. like 77mm plate resists 76mm APCBC hit at 30 deg. like 93mm plate resists 75mm M72 AP hit at 0 deg. like 90mm plate resists 90mm APCBC hit at 45 deg. like 88mm Tiger 82mm plates did pretty well that day.

"The new turret had an enitrely redesigned front, include changes in the cg such that more weight on the front *was* possible." The changes in the shape and turret weight do not appear to be radical. It was the gun that unbalanced the turret, not the armor layout, and putting more thickness on the turret front and mantlet is not going to improve things with regard to the center of gravity, it is going to make it worse. The turret weight issue is still alive for the IS-2 tanks regardless of some minor changes in shape and thickness. "Without the weight argument to resort to then, we can only look at the german/british measurements of the tanks, but if you take another look at the photo from yahoo tankers, you will see it is an *early* variant, thus the thickness of the *early* mantlet was roughly the 110mm figure painted on it by the germans. Could the discrepancy with the British figures then have something to do with measurements coming from both an early and a late tank?" The British had the same mantlet and turret front armor on all IS-1 and IS-2 tanks, which was only slightly less (100mm vs 110mm) than the Germans stenciled on the early IS-2. Looking at the British figures there is nothing to suggest 160mm for the typical mantlet thickness that a hit will have to defeat. The British had 100mm for the mantlet with a small area of 60mm turret front that the mantlet overlapped, and the ballistic resistance value of the 60mm would be negligible. There could be small isolated areas on the late model IS-2 mantlet and turret front where 160mm existed, maybe around the gun barrel and at the edges of the turret front where it met the mantlet (to reduce the impact of edge effects, which decreases armor resistance). But the typical thickness that a hit would have to defeat would seem to be 110mm and 100mm (mantlet and turret front) regardless of maximum thickness. Maximum and minimum armor thicknesses really tell one little about the typical resistance. [ August 07, 2003, 10:45 PM: Message edited by: rexford ]

"It gives a 120mm figure for the hull armor and 160 for the thickest part of the turret." Does it identify where the thickest parts were and how large an area they covered? Could be a small area. Using the thickest sections of an armor plate is not a very exact way to express things, since small local areas may be designed thicker than 95% of the area. A small area around the gun or a vision port could be the max. The IS-1 and IS-2 mantlet is curved and tapered, with 76mm at the upper and lower edges and a maximum in the middle (the apex). So one figure for the mantlet thickness is not correct, and one Russian book actually stated 76mm for the IS-2 mantlet thickness (forget which reference). I'am not sure what the "improvement" to the IS-2 turret armor means. Could be more thickness, or maybe just that mantlet armor was more resistant than turret front (if mantlet is 110mm thick and turret front is 100mm, using a wider mantlet means more area is protected by 110mm as opposed to 100mm). So turret armor "improvement" could be a higher average thickness when mantlet and turret front armor combine for an average thickness, with a greater area of mantlet on later tanks. The unbalancing of the IS-2 turret by the 122mm gun is not going to be undone by some relatively minor changes in the IS-2 turret armor layout or shape, since the turret configuration did not change that much. Compare the IS-1 and IS-2 late model turret shape and armor thicknesses: they are similar. From my past examinations of photo's and scale models, the KV-85 and IS-2 turrets look very much alike (I made IS-1 tanks by taking the KV-85 turret and placing it on an early model IS-2), although I haven't really done a scientific analysis. There are sources that use 120mm for the IS-2 nose armor (lower front hull), and others that state 100mm. Drawings on the Russian Battlefield show 100mm. But that is another issue. Please note that rounded Panther mantlet stayed at 100mm cast and rounded through D, A and G models, and was also tapered with thinner thickness at upper/lower edges. Even after the IS-2 and ISU-122 appeared, and with full knowledge of what SU-152 and ISU-152 hits could do, Panther mantlet stayed the same thickness (suggests that thickness was determined by factors other than enemy weapon performance). Russian sources state 120mm for IS-1 and IS-2 early front upper hull, which might be continued for late model IS-2 if the author of a book is not careful. The thickness of the late model IS-2 glacis is an interesting point, but whether 100mm or 120mm the 88L71 APCBC is going to bounce off the 60 degree from vertical slope. At 90mm rolled armor and 60 degree slope, 88L71 is still going to bounce at just about every combat range, which would seem to be the design objective of the glacis armor. [ August 07, 2003, 10:31 PM: Message edited by: rexford ]

The original narrow mantlet width was designed for the 85mm gun IS-1, where the barrel was relatively narrow and did not have a muzzle brake. The gunsight on the original narrow mantlet IS-1 worked just fine cause the gun did not get in the way when one was sighting a moving target. I don't believe there were plans to upgun to 122mm when the IS-1 was first designed, based on the mantlet design. But only 108 or so IS-1 were built before the Russians went with 122mm guns due to inadequacy of 85mm against Tigers and Panthers. The first IS-2 with the narrow mantlet and 122mm gun with large muzzle brake fouled things up, cause the gun barrel and brake got in the gunners way when trying to lead a moving target. The mantlet width was increased so the gunner could see around the long and wide 122mm gun barrel and not be blocked by the muzzle brake. The Russian Battlefield site states that the turret armor and weight could not be increased due to the unbalanced turret weight, where the original turret design was for an 85mm gun. The much heavier 122mm gun messed up the turret balance. A post on the Yahoo!Tankers site showed a 110mm mantlet thickness stenciled on an IS-2 that the Germans had captured. British Intelligence figures on the IS-2 mantlet and turret front did not exceed 100mm, which could be due to casting variations (Russians used casting molds till they fell apart, and maybe a little while afterwards). The 160mm width may come from some British figures where the basic mantlet was shown as 100mm and there was a small lip of the turret front that extended below the mantlet left/right edges a small bit. Add the two and it is about 160mm, but the small lip would suffer from edge effects and would not really add much. Drawings of the IS-2 mantlet side view show a big thickening around the gun, which might scale as around 160mm. The "best data" appears to be the German thicknesses stenciled on captured IS-2 tanks, 110mm mantlet and 100mm turret front. Actual wartime measurements (maybe), or figures copied from Russian tank crew manuals (could be). Anyway, odds are that early IS-2 and late IS-2 had same turret and mantlet thicknesses if one takes the weight restriction commentary at face value. [ August 07, 2003, 06:56 PM: Message edited by: rexford ]

Good point.