rexford

Quite a few folks have e-mailed me over a several month period regarding the subject armor thickness, which is 127mm in British documents but alot less in many Russian sources. We had Vasiliy Fofanov search out current Russian figures for Model 1944 IS-2 lower front hull armor (30 degrees from vertical), and he found 90mm rolled homogeneous or 100mm cast homogeneous. The Russian Battlefield shows several drawings with 100mm at 30 degrees from vertical cast armor for IS-2 Model 1944. The thickness of the 60 degree glacis armor could also stand another close look. This subject is important and may be worth some additional study before we close the door on future CMBB patches.

Amedeo Mateucci sent me an e-mail regarding Russian cannister which seems very valid. http://www.geocities.com/Pentagon/Base/1852/57mm.html#24 lists three different cannister rounds for 45mm guns during WW II. http://www.battlefield.ru/guns/project_1.html has cannister for 45mm, 57mm and 76.2mm guns. The game system should be revised to incorporate something on 45mm cannister, and maybe 57mm cannoister. Amedeo appears to have read some things about 45mm cannister use during the GPW and the ammo appears to warrant some consideration. If more info is needed I can ask him for references and additional data. I have not discussed 57mm cannister much with Amedeo but will ask him what he knows about it.

When Russian AP hits the face-hardened armor on PzKpfw III and IV, the thin face-hardened layer is usually harder than the projectile nose. 51 to 60 Rockwell C hardness for face-hardened armor layer, about 52 average Rockwell C for Russian AP. Theory with face-hardened armor is that the layer is harder than the projectile, causing the nose of the round to crack, fracture or shatter and thereby absorb energy that otherwise would go into the destruction of the armor. With Russian APCR, projectile nose is 67 Rockwell C, which will be harder than the face-hardened armor layer. The tungsten hardness may change the equation so that the projectile gains the upper hand, but info to support such a theory is rare. The John Salt site offers a ton of penetration stats for 17 pdr APDS, and only one is associated with face-hardened armor. Hogg, in his 1997 "Tank Killers", presents a figure of 231mm penetration at 1000 yards and 30 degrees slope for 17 pdr APDS against face-hardened armor. Against homogeneous armor, the 17 pdr APDS is credited with 188mm at 30 degrees. Assuming a 30 degree slope effect of 1.24 for 17 pdr APDS yields a vertical penetration ratio at 1000 yards of 286mm face-hardened/232mm homogeneous, for 1.23. So 17 pdr APDS might penetrate 23% more face-hardened armor at 1000 yards than homogeneous. It seems realistic to assume tungsten does better against face-hardened than homogeneous. One case does not prove anything to the degree we would like. But then again, we don't know if the Russian penetration figures put forth for their APCR are against homogeneous armor, high hardness homogeneous or face-hardened armor (an issue that Miles Krogfus may address in his upcoming AFV News article). Giving tungsten core rounds a boost against face-hardened armor would help against PzKpfw IIIH and PzKpfw IVG,H and J frontal armor. But is that boost already in the stats?

Russian firing tests supposedly indicated the following results for 45mm, 57mm and 76.2mm APCR against Tiger II side armor (80mm at 25 degrees from vertical hull side); "The Russian tactics for combating the Tiger II were found in the following pamphlet written by Lt. Col. J. D. Skrobow and Lt. Col. A. N.Bukirew on ?The German heavy tank "Tiger-B" (Koenigstiger) and How To Combat It?, translated by the 17 .Armee on 4 February 1945: ... All of the anti-tank guns in the Red Army can penetrate every armor plate on the Tiger-B ____with the exception of the front plates____. ... Firing trials have revealed that the side armor on the turret and superstructure of the Koenigstiger can be penetrated at ranges up to: -0 meters by the 45 mm anti-tank gun (sub-caliber and AP) -600 meter by the 57mm anti-tank gun (sub-caliber) -400 meters by the 76 mm ZIS-3 anti-tank gun (sub caliber)" If we apply a 1.23 slope multiplier for 25 degree slope against tungsten core ammo and multiply by the 80mm side hull armor on Tiger II (superstructure side), we obtain 98mm vertical resistance. The 76mm HVAP based penetration estimates for 76.2mm APCR predict 96mm vertical penetration at 400m, which is close to the estimated resistance of the armor. 45mm APCR is predicted to penetrate 120mm at 0m in the DeMarre equation analysis, which looks high. If the 120mm DeMarre penetration estimate at 0m is multiplied by 75mm (Russian figure at 500m) divided by 86mm (DeMarre estimate at 500m), the result is 105mm which looks high unless smaller APCR has higher slope effects. If the 57mm APCR penetration is assumed to take place with a 30 degree side angle, the estimatedarmor resistance is 142mm vertical while the HVAP based penetration estimate is 150mm and the Russian figure is 135mm. The above analysis shows that there are problems with the 76mm HVAP based estimates for 45mm APCR penetration, and the 57mm APCR DeMarre estimates are not consistent with firing tests against Tiger II side armor.

An American report entitled REVIEW OF SOVIET ORDNANCE METALLURGY, by A. Hurlich and dated April 1953, provides data on the diameter and weight of the 45mm APCR round and tungsten core. The 45mm tungsten core weighed 0.25 kg and was 18.7mm in diameter, the entire projectile weighted 0.85 kg. Based on muzzle velocities of 970 m/s and 1070 m/s for 45mm APCR, use of a trajectory computer program by Jurens and Okun, and a DeMarre penetration estimate from U.S. 76mm HVAP, the following penetration estimates were prepared for 45mm APCR against medium hardness rolled homogeneous armor: 45mm APCR from 45mm L46 gun =========================== 000m, 120mm 050m, 116mm 100m, 113mm 150m, 109mm 200m, 106mm 250m, 102mm 500m, 86mm 750m, 73mm 45mm APCR from 45mm L66 gun =========================== 000m, 138mm 050m, 134mm 100m, 130mm 150m, 126mm 200m, 123mm 250m, 118mm 500m, 100mm 750m, 085mm Official Russian firing test data predicts 75mm penetration for 45mm L46 APCR at 500m, which is quite a bit below the above estimates. There is a possibility that the tungsten cores in 45mm APCR may have been "inferior" to 57mm, 76.2mm and 85mm cores, or the core dimensions given in the report may have been for later post-WW II projectiles and a smaller less effective APCR was used in 45mm gun during WW II. Since the Hurlich report shows that 45mm APCR did not differ much from the other Russian APCR cores in terms of chemical composition and nose hardness (86 Rockwell C), it would seem that a smaller WW II core may be responsible for reported penetration during WW II but this is speculation at this point. The 45mm tungsten core is superior to the 76.2mm core in terms of penetrator density, or weight divided by core diameter cubed. 45mm density equals 0.25 kg/18.7mm cubed or 0.00003823, while the 76.2mm core is 0.48 kg/27.9mm cubed for 0.00002210. Since one of the terms in the DeMarre penetration equation equals the relative density raised to the 0.7143 power, the 45mm core density results in an 48% penetration advantage for 45mm APCR due to relative density. The relative density advantage of 45mm APCR over 76.2mm APCR is offset by the smaller diameter core, which results in a penetration multiplier of (18.7/27.9) raised to the 1.07143 or 0.65. The Russian penetration estimates for 45mm APCR fired from the T70 gun display some penetration losses with range that bring the figures into question: 45mm L46 APCR ============= 0500m, 75mm vertical penetration, 60mm at 30 degrees from vertical 1000m, 59mm vertical penetration, 54mm at 30 degrees from vertical 1500m, 54mm vertical penetration, 51mm at 30 degrees from vertical If the round losses 16mm vertical penetration from 500m to 1000m, it should lose more than 5mm from 1000m to 1500m based on my velocity estimates. It appears that the Russians may have used questionable velocity-vs-range figures. It appears that all WW II Russian APCR contained mercury compounds which would release toxic gases inside a vehicle after penetration.

Go to following site for some neat stuff about 45mm cannister: http://www.geocities.com/Pentagon/Base/1852/57mm.html#24 Also be sure to note existence of 45mm cannister rounds during WW II in three varieties. Following site notes that 45mm gun was used with great effect against infantry in Korea, which may be due to cannister(?): http://www.rt66.com/~korteng/SmallArms/rok5.htm [ March 28, 2003, 06:12 PM: Message edited by: rexford ]

Go to following site for some neat stuff about 45mm APCR: http://www.geocities.com/Pentagon/Base/1852/57mm.html#24 45mm APCR round contained solid mercury compounds that were converted to a toxic gas upon penetration. Bad for crew of penetrated panzer. I don't know if 57mm, 76.2mm and 85mm APCR contained that mercury mix, but the small core in a 45mm APCR projectile would become quite lethal if it released toxic flumes. Also be sure to note existence of 45mm cannister rounds. Following site notes that 45mm gun was used with great effect against infantry in Korea, which may be due to cannister(?): http://www.rt66.com/~korteng/SmallArms/rok5.htm

If the Russian figures at 100m, 500m and 1000m for 57mm APCR are extrapolated, the estimates become: 0m, 206mm 50m, 199mm 100m, 192mm 150m, 185mm 200m, 179mm 250m, 172mm 500m, 145mm 750m, 121mm 1000m, 102mm The tungsten core round fired by 57mm L73 guns can sure defeat thick armor, being able to take on the Tiger frontally at 500m and piere just about any armor area. And the round should have lots of energy left once it gets inside a panzer. On the other hand, the 57mm tungsten core is less than an inch across, and tungsten rounds had a tendency to shatter on hits with any kind of angle.

Gathering up as much info as was available and making adjustments to trajectory model for arrowhead APCR yields following penetration figures, based on a DeMarre estimate from U.S. 76mm HVAP (247mm penetration with 38.1mm core diameter, 1.76 kg core weight and 1037 m/s muzzle velocity): =================================== 57mm APCR 24.13mm tungsten core diameter, 0.51 kg core weight. 1200 m/s muzzle velocity, Penetration estimate might be reduced below following figures due to material ahead of nose which acts as armor piercing cap (and windscreen): 000m, 205mm penetration of rolled homogeneous armor plate 050m, 200mm 100m, 195mm 150m, 190mm 200m, 185mm 250m, 180mm 500m, 158mm 750m, 138mm 1000m, 120mm Russian figures show 190mm at 100m, 145mm at 500m and 105mm at 1000m, about 15mm lower than DeMarre estimates. If the Russian figures are extrapolated to 0m the result is 206mm (76mm HVAP based estimate for 0m is 205mm). ================================== 76.2mm APCR 27.94mm tungsten core diameter, 0.48 kg core weight. 965 m/s muzzle velocity, Nose of tungsten core is not shielded by solid material used as a cap. 000m, 123mm penetration of rolled homogeneous armor plate 050m, 119mm 100m, 116mm 150m, 112mm 200m, 109mm 250m, 105mm 500m, 090mm 750m, 076mm 1000m, 063mm Above figures consistent with Russian data, 92mm at 500m and 62mm at 1000m. ================================= 85mm APCR 27.51mm tungsten core diameter, 0.64 kg core weight. 1050 m/s muzzle velocity, Penetration estimate might be reduced below following figures due to material ahead of nose which acts as armor piercing cap (and windscreen): 000m, 173mm penetration of rolled homogeneous armor plate 050m, 170mm 100m, 166mm 150m, 163mm 200m, 160mm 250m, 157mm 500m, 142mm 750m, 128mm 1000m, 115mm Russian figures show 140mm at 500m and 118mm at 1000m. =============================== DeMarre estimates from U.S. 76mm HVAP are close to Russian firing test figures for 76.2mm and 85mm APCR. Size of tungsten cores is unusual, 76.2mm and 85mm APCR have about the same diameter core, and 57mm APCR core is heavier than 76.2mm core although the 57mm core is smaller in diameter. Would appreciate following information on 45mm APCR, tungsten core diameter and weight nose length in terms of projectile diameter (a drawing would be best). Thank you. Velocities used in DeMarre equation derived from trajectory computer program prepared by Bill Jurens and Nathan Okun. Information on program inputs will be furnished upon request. Data on Russian APCR projectiles and cores taken from Yahoo!Tankers files, particulars available upon request. The above figures for 76.2mm and 85mm APCR are lower than what the game uses. Net Surfer Bird

I've read of Grants in the desert that aimed at and hit 88mm Flak gun shields. Hitting the shield of a properly dug-in gun is not so easy, but it did happen. Since HE rounds throw out many of the fragments to the side of the impact point, one good aiming tactic would seem to have guns aiming to the side of the target gun. This way bursts could sweep the crew in back of the shield. But this is mostly speculation since I haven't read that much on the subject. One Russian field gun crewman wrote that they had one man at a time attending to the gun (either loading or aiming/firing) while the others hid in their holes. This way only one trained crewmen was lost when the gun was hit, a lesson learned at Kursk after too many trained and competent men were lost while they camped around the gun. Following passage deals with direct hits on guns, where German tanks had good skills in hitting Russian guns, and is found at: http://www.iremember.ru/artillerymen/monyushko/monyushko2.htm "Of course, not only artillery participated in the fighting for the bridgehead, and representatives of other branches of military service, other military specializations, saw everything that went on differently, from different points of view. To me and, as I can judge from converstaions with comrades, to the soldiers of my regiment the scheme of the fighting was the following: After short but powerful artillery raids the Germans would attack with their armor. Heavy AFVs, Tigers and Ferdinands, ascended hills deep inside the German positions and stopped 1-1.5 kilometers from our own positions. The lighter and more maneuverable Pz.IV's continued to advance together with small numbers of infantry. It made little sense for us to fire at the AFVs deployed in the rear. Even in case of a direct hit the shell couldn't cause serious damage at such range. But German tankers waited until our anti-tank battery was forced to open fire at the tanks advancing in the front. A gun that opened fire, exposed itself, immediately fell victim to a well aimed shot from the stationary heavy AFVs. It must be noted that Tigers had very precise sights and very accurate 88mm guns. This explains the advice that I received about not opening fire until the last moment. When opening fire from a "pistol shot range" you could expect to hit with the first or, in an extreme case, the second shell, and then, even if the gun was destroyed, you could still get an "exchange of figures" disadvantageous to the Germans - a tank for a light gun. But if you exposed your position prematurely the gun most probably would've been lost in vain. This also explained the additional changes introduced to a typical structure of an artillery ditch. Two holes were made to the left and right of a gun's wheels - one for the gunner, the other for the loader. Practically, ZIS-3 guns didn't require simultaneous presence of the entire crew near the gun. Moreover, it was usually enough for only one person to be present. The gunner, after firing, could hide himself in his hole while the loader would drive the next shell into the barrel. Now the gunner could take his place, aim, and fire, and the loader would be taking cover at that time. Even after a direct hit into the gun at least one of the two had a chance to survive. The other crew members were spread out through the holes, side "pockets" of the trench. Practical experience, which was being accumulated in this regiment starting as far back as the Batttle of the Kursk Salient, allowed to minimize casualties. Over the one and a half months of fighting in the bridgehead, the regiment replaced its equipment three times, getting new and repaired guns to replace damaged and destroyed ones, and kept its fighting efficiency while getting almost no replacements in men."

Go to following site for a very intelligent discussion of tank combat in general, and Tigers in one case: http://www.iremember.ru/tankers/loza/loza1.html Note the following tactic used to defeat Tigers with TWO RUSSIAN SHERMANS, something the Allies never thought of!!!!!!!!!!!!!!! "What would you like to say about the German Tiger? - It was an extremely heavy vehicle. The Sherman could never defeat a Tiger with a frontal shot. We had to force the Tiger to expose its flank. If we were defending and the Germans were attacking, we had a special tactic. Two Shermans were designated for each Tiger. The first Sherman fired at the track and broke it. For a brief space of time the heavy vehicle still moved forward on one track, which caused it to turn. At this moment the second Sherman shot it in the side, trying to hit the fuel cell. This is how we did it. One German tank was defeated by two of ours, therefore the victory was credited to both crews. There is a story about this entitled "Hunting With Borzois" in my book." Russians out thought and out fought the Americans and Allies in the above case when it came to Tigers! Allies expected to lose several Shermans getting a Tiger, Russians tried not to lose any!

The following site has an interesting discussion of how Tigers were used against anti-tank guns, and Russian comments on Tiger tank optics quality and gun accuracy: http://www.iremember.ru/artillerymen/monyushko/monyushko2.htm "After short but powerful artillery raids the Germans would attack with their armor. Heavy AFVs, Tigers and Ferdinands, ascended hills deep inside the German positions and stopped 1-1.5 kilometers from our own positions. The lighter and more maneuverable Pz.IV's continued to advance together with small numbers of infantry. It made little sense for us to fire at the AFVs deployed in the rear. Even in case of a direct hit the shell couldn't cause serious damage at such range. But German tankers waited until our anti-tank battery was forced to open fire at the tanks advancing in the front. A gun that opened fire, exposed itself, immediately fell victim to a well aimed shot from the stationary heavy AFVs. It must be noted that Tigers had very precise sights and very accurate 88mm guns." Given a long clear line of fire, it appears that Tigers could be very effective against guns. Reports of Tiger damage to Russian forces usually include a healthy number of guns, tanks and motor vehicles. The Tiger fired HE rounds at 810 m/s, which is higher than the Panther (700 m/s) and Tiger II (750 m/s), which might account for the accuracy against guns.

The following site has an interesting discussion of how Tigers were used against anti-tank guns, and Russian comments on Tiger tank optics quality and gun accuracy: http://www.iremember.ru/artillerymen/monyushko/monyushko2.htm "After short but powerful artillery raids the Germans would attack with their armor. Heavy AFVs, Tigers and Ferdinands, ascended hills deep inside the German positions and stopped 1-1.5 kilometers from our own positions. The lighter and more maneuverable Pz.IV's continued to advance together with small numbers of infantry. It made little sense for us to fire at the AFVs deployed in the rear. Even in case of a direct hit the shell couldn't cause serious damage at such range. But German tankers waited until our anti-tank battery was forced to open fire at the tanks advancing in the front. A gun that opened fire, exposed itself, immediately fell victim to a well aimed shot from the stationary heavy AFVs. It must be noted that Tigers had very precise sights and very accurate 88mm guns." Given a long clear line of fire, it appears that Tigers could be very effective against guns. Reports of Tiger damage to Russian forces usually include a healthy number of guns, tanks and motor vehicles. The Tiger fired HE rounds at 810 m/s, which is higher than the Panther (700 m/s) and Tiger II (750 m/s), which might account for the accuracy against guns.

The Tiger Fibel presents a method of aiming at 2m high targets that suggests a high percentage of first shot hits (see http://www.geocities.com/tigerfibel/tigerfibel.htm and look in the section on Elvira wird erschossen, under Richtschuetze). Setting the gun elevation for a 940m range and aiming at the bottom of the target results in a mean trajectory that will never be more than 2m above the target bottom, suggesting that every shot hits the target. While the use of the above aim process suggests a very high first shot accuracy, center of mass aim with a range estimate for each situation can be more effective over a wide range of target distances. The aiming method described in the Tiger Fibel for targets to 940m range, which is sometimes referred to as battlesight aim, was compared to center of mass aim by computing the first shot hit percentage. Random round to round scatter was applied to the theoretical trajectory, and center of mass aim was based on average range estimation errors of 10% (what Tiger crew was expected to attain) and 25% (average crew level). Averaging the hit probability at each range from 200m to 940m in 100m increments shows that center of mass aim with 10% average range estimate error is superior to the other cases: Battlesight aim, 75% average hit probability from 200m to 940m Center of mass aim with 10% average range error, 92% average hit chance Center of mass aim with 25% average range error, 71% average hit percentage The less than 100% hit chance with battlesight aim is due to the large number of shots where the mean trajectory is near the bottom or top of the target and scatter drives the shot off the target. The following table shows that for targets at 400m to 600m range, and 900m to 940m, the trajectory is very close to the target edge. Battlesight trajectory over bottom of 2m high target, 940m aim at bottom of target =========================================================== 200m, 1.31m trajectory height over target bottom at range 300m, 1.72m 400m, 1.95m 500m, 2.00m 600m, 1.87m 700m, 1.56m 800m, 1.05m 900m, 0.35m 940m, 0.00m 1000m, -0.55m 1100m, -1.65m If the average hit probability is computed from 200m to 1100m, which takes into account targets beyond 940m that are estimated to be within 940m, the disadvantage of battlesight aim to center of mass aim with 10% range error becomes even more pronounced: Battlesight aim, 63% average hit percentage from 200m to 1100m Center of mass aim with 25% average range error, 63% average hit chance Center of mass aim with 10% average range error, 86% average hit probability A Tiger crew with better than average range estimation error would find alot more of their first shots hitting with center of mass aim. One of the main advantages of battlesight aim is the reduction in time spent on first shot range estimation, since one only has to decide if the target is within 940m of the Tiger (which provides a possible error).

Forgot how to delete a response. [ February 23, 2003, 07:51 AM: Message edited by: rexford ]

My fault, too early in the morning. [ February 23, 2003, 07:55 AM: Message edited by: rexford ]

The Tiger Fibel presents a method of aiming at 2m high targets that suggests a high percentage of first shot hits (see http://www.geocities.com/tigerfibel/tigerfibel.htm and look in the section on Elvira wird erschossen, under Richtschuetze). Setting the gun elevation for a 940m range and aiming at the bottom of the target results in a mean trajectory that will never be more than 2m above the target bottom, suggesting that every shot hits the target. While the use of the above aim process suggests a very high first shot accuracy, center of mass aim with a range estimate for each situation can be more effective over a wide range of target distances. The aiming method described in the Tiger Fibel for targets to 940m range, which is sometimes referred to as battlesight aim, was compared to center of mass aim by computing the first shot hit percentage. Random round to round scatter was applied to the theoretical trajectory, and center of mass aim was based on average range estimation errors of 10% (what Tiger crew was expected to attain) and 25% (average crew level). Averaging the hit probability at each range from 200m to 940m in 100m increments shows that center of mass aim with 10% average range estimate error is superior to the other cases: Battlesight aim, 75% average hit probability from 200m to 940m Center of mass aim with 10% average range error, 92% average hit chance Center of mass aim with 25% average range error, 71% average hit percentage The less than 100% hit chance with battlesight aim is due to the large number of shots where the mean trajectory is near the bottom or top of the target and scatter drives the shot off the target. The following table shows that for targets at 400m to 600m range, and 900m to 940m, the trajectory is very close to the target edge. Battlesight trajectory over bottom of 2m high target, 940m aim at bottom of target =========================================================== 200m, 1.31m trajectory height over target bottom at range 300m, 1.72m 400m, 1.95m 500m, 2.00m 600m, 1.87m 700m, 1.56m 800m, 1.05m 900m, 0.35m 940m, 0.00m 1000m, -0.55m 1100m, -1.65m If the average hit probability is computed from 200m to 1100m, which takes into account targets beyond 940m that are estimated to be within 940m, the disadvantage of battlesight aim to center of mass aim with 10% range error becomes even more pronounced: Battlesight aim, 63% average hit percentage from 200m to 1100m Center of mass aim with 25% average range error, 63% average hit chance Center of mass aim with 10% average range error, 86% average hit probability A Tiger crew with better than average range estimation error would find alot more of their first shots hitting with center of mass aim. One of the main advantages of battlesight aim is the reduction in time spent on first shot range estimation, since one only has to decide if the target is within 940m of the Tiger (which provide an error).

The following site has an interesting discussion of how Tigers were used against anti-tank guns, and Russian comments on Tiger tank optics quality and gun accuracy: http://www.iremember.ru/artillerymen/monyushko/monyushko2.htm "After short but powerful artillery raids the Germans would attack with their armor. Heavy AFVs, Tigers and Ferdinands, ascended hills deep inside the German positions and stopped 1-1.5 kilometers from our own positions. The lighter and more maneuverable Pz.IV's continued to advance together with small numbers of infantry. It made little sense for us to fire at the AFVs deployed in the rear. Even in case of a direct hit the shell couldn't cause serious damage at such range. But German tankers waited until our anti-tank battery was forced to open fire at the tanks advancing in the front. A gun that opened fire, exposed itself, immediately fell victim to a well aimed shot from the stationary heavy AFVs. It must be noted that Tigers had very precise sights and very accurate 88mm guns." The article further states that the losses to anti-tank gun crews at Kursk lead one regiment to pursue a tactic where only one crew member would be near the gun at a time, with the rest in holes away from the gun. While that tactic would reduce the rate of fire, it was noted for its' ability to conserve trained crew members.

The Tiger turret side and rear is curved, which will add some additional protection on a percentage of hits.

Curved armor is usually the weakest point on a target cause it is cast, and is usually on the front of the turret where weight and thickness have to be held down. With center of target mass aim, the bottom of the mantlet gets hit more often than the middle section. We've seen many German pictures of IS-2 tanks with holes in the turret front from 88L71 hits at 2000m. But the German pictures do not show the hits that bounced off an IS-2 and allowed the 122mm gun to zero in on the 88L71 Pak or Nashorn.

It seemed that 8mm armor would be less resistant than 40mm armor at the same Thickness/Diameter ratio, where 380mm rounds hit the 40mm and 75mm hit the 8mm. So we're talking large ammo against really thin plates, but at a very long range. At normal combat ranges the lowered resistance of thin plates should not be a factor against big projectiles. For small projectiles like machine guns and anti-tank rifles, the penetration data is against thin plates so no big change. So the thin plate effect should not really have much impact on CMBO or CMBB.

Same person. Thanks for nice words.

Robert Livingston has noted that scale effects may lead to greater resistance of an 80mm plate as opposed to 16mm armor. U.S. analysis of firing test results theorized that the surfaces on a plate offer less resistance than the interior areas, since the outer surfaces are not tightly supported and are relatively free to move vertically and laterally. This would suggest that an 80mm plate would outperform a 16mm plate when both were hit at the same angle and T/D ratio. The above explanation appears to offer a reasonable explanation of the deviations from our curves.

Robert Livingston has noted that scale effects may lead to greater resistance of an 80mm plate as opposed to 16mm armor. U.S. analysis of firing test results theorized that the surfaces on a plate offer less resistance than the interior areas, since the outer surfaces are not tightly supported and are relatively free to move vertically and laterally. This would suggest that an 80mm plate would outperform a 16mm plate when both were hit at the same angle and T/D ratio. The above explanation appears to offer a reasonable explanation of the deviations from our curves.

The following web site has some penetration vs angle curves for German 380mm APCBC ammo, which brings up an interesting aspect of slope effect analysis. http://www.warships1.com/W-INRO/INRO_Hood_p2.htm Our base data for APCBC slope effects is limited to a range where the T/D ratio ranges from low to high figures, but does not really reach very low ratio's. I have read where thin plate gains added resistance from stretching, which suggests that our slope multiplier vs T/D ratio's for each angle may not work well at very low T/D. Here is an analysis of 380mm APCBC slope effects vs T/D ratio with comparison to estimates using our equations; 380mm APCBC at 250 m/s penetrates 200mm at vertical and 80mm at 57 degrees from vertical 2.50 slope multiplier when T/D = 0.211 (80mm/380mm) If U.S. 75mm APCBC hit 16mm at 57 degree armor (T/D = 0.211), the slope effect would be about 1.88 from our equations. 380mm APCBC at 170 m/s penetrates 120mm at vertical and 40mm at 67 degrees from vertical 3.00 slope multiplier when T/D = 0.105 (40mm/380mm) If U.S. 75mm APCBC hit 8mm plate at 67 degrees (T/D = 0.105), the slope effect would be 2.13 from our equations. 380mm APCBC at 120 m/s penetrates 80mm at vertical and 40mm at 57.5 degrees from vertical 2.00 slope multiplier when T/D = 0.105 (40mm/380mm) U.S. 75mm APCBC against 8mm at 57.5 (T/D = 0.105) would have a slope effect of 1.63 from our equations. It may be that our models don't consider hits on very thin armor where the stretching of the plate comes into play. Our base data may not go to really low T/D ratio's.