rexford

For the first shot by an IS-2 tank at a German 75mm anti-tank gun position, the average range estimate error would be about 25% of the range, which can also be used as the standard deviation for range errors. At 300m, 600m and 1000m range, the IS-2 would be firing, on average, at a ground point 75mm, 150m and 250m away from the actual target location. Ground scatter standard deviation for the 122mm HE round at the abovenoted ranges is 14m, 39m and 46m about the aim point, resulting in final first shot standard deviations of 76m, 155m and 255m. 122mm HE impact boxes for men standing in open would be: 75% casualty probability per man up to 10m in front of HE ground detonation 30% casualty probability from 10m to 19m in front of detonation point 5.5% casualty probability from 19m to 54m in front of detonation point Applying the final standard deviations for the first shot to the above impact distances produces: 6% probability that first shot at 300m target will fall close enough to injure men in open 3% at 600m 2% at 1000m Since the 75mm ATG gun crew may be in a dug in position shielded from fragments, and the men may be crouching, the probability that a first shot 122mm HE round will injure someone is small. Fragment related casualties are not the entire picture, since close misses may cause the gun crew to duck or may pin them for a longer time. If the 122mm HE round were fired at 10 infantry running in the open at 300m, the 6% probability would be applied to each man in turn. The outer dimensions of the impact boxes are: 10m depth x 65m width for 75% average casualties against men in open 19m depth x 129m width for 30% 54m depth x 356m width for 5.5% The above dimensions were calculated based on British 25 pdr HE area with appropriate adjustments for shell size. Many sources for HE blast area fragment densities give dimensions twice what I have used for same probability, so there is no one true figure. There were also differences in metal quality between nations Based on ground scatter considerations and 0m range estimate error, max chance for an HE hit to potentially impact troops standing in open is: 29% at 300m 12% at 600m 10% at 1000m To effectively silence a 75mm Pak, it appears that a group fire by IS-2 tanks would be required. As noted above, some sources double the depth dimension I used so the above probabilities would be roughly doubled if an alternative approach is pursued, and the size of the box might be increased if Russian 122mm HE fragmentation rounds were assumed to use more effective explosives and metal than the British 25 pdr HE.. =================================================================== The ground scatter standard deviation for direct HE fire is a function of velocity, with slower moving projectiles having less ground scatter: GROUND SCATTER STANDARD DEVIATION ALONG FIRE DIRECTION 800 m/s HE muzzle velocity (analysis of 88L56 and 122mmL46 firing tables) 14m at 300m, 39m at 600m, 50m at 1000m, 52m at 1800m 550 m/s HE muzzle velocity (German 75L48, American 75L40 super charge, 17 pdr HE) 19m at 300m, 33m at 600m, 38m at 1000m, 37m at 1800m 305 m/s HE muzzle velocity (British 95mm and 75L40) 6m at 300m, 10m at 600m, 16m at 1000m and 35m at 1800m 238 m/s HE muzzle velocity (U.S. 105mm) Same as 305m m/s except 15m at 1000m and 22m at 1800m The above stats for ground scatter indicate that if the range error were zero at 1000m and the depth of the HE impact box were similar to 122mm HE, the max injury probabilities for each HE muzzle velocity against a man standing in the open would be: 10% for 800 m/s 12% for 550 m/s 27% for 305 m/s 28% for 238 m/s Low velocity direct HE fire appears to have a benefit in terms of near misses that are close enough to cause injury or death. High velocity HE fire would, however, have a higher probability of hitting a sandbag emplacement or gun on the fly, which is not included in the above calculations. As noted above, injuries due to fragment hits are not the only source of benefit from HE blasts. Gun crews may be pinned or have their morale shaken for some time, infantry may be forced to ground or pinned so they do not fire effectively, etc. ============================================================================ British firing tests with 5.5" guns shooting 100 pound HE shells resulted in the following conclusions for indirect fire (which is more effective than direct fire in terms of lethal area dimensions) : Against German 105mm howitzer: 700 square feet lethal area to prevent accurate fire for several hours with gun in open 100 square feet lethal area for complete destruction with gun in open 300 square foot lethal area to prevent accurate fire for several hours against 20' diameter gun pit An 88mm gun in the open would have lethal areas of 1000 square feet for prevention of accurate fire for several hours and 100 square feet for complete destruction. Above results were obtained from Nigel Evans. [ June 02, 2002, 08:34 PM: Message edited by: rexford ]

It turned out that majority of IS-2 tanks had rounded 100mm turret front and mantlet, compared to 120mm at 60° on glacis. So turret front/mantlet was much more vulnerable and a better shot. Russian Shermans in Russia fired at Tiger tracks, Russian anti-tank rifles fired at vision slits, hull MG mounts and the smoke dischargers on the Tiger turret. Hitting smoke discharger could cause all sorts of problems when they went off, and this is why they were discontinued. Directed aim occurred and sometimes worked. Problem is that under stress of combat, many forget everything they have been taught or learned. My favorite example is a 75mm armed Sherman face to face with a Panther. The Sherman hit the Panther glacis and continued firing at the same point cause they were getting accurate hits, even though they bounced. The Panther crew realized the first Sherman would continue the useless but accurate fire and rotated its turret to pick off another Sherman, betting that the accurate Sherman would not change target area. And it didn't. It is not so easy to think logically on a battlefield during combat.

It is good to see your posts on this site. Your review of our HE "hit" probability method is on the mark. We threw in longitudinal ground scatter due to the interaction of vertical dispersion and impact angle (range ground scatter is given on German ballistic tables we have). We have German ballistic tables for APC, APCBC and HE that give descent angles every 100 meters out to fairly good range, plus our book, WW II BALLISTICS, calculates and presents descent angles for Russian, German, U.S. and British AP, APC, APCBC and tungsten core rounds using equations we received from Alvaro Figueiras. Descent angles every 100m out to 3000m. I received your order for the WW II BALLISTICS book and are having a copy printed right now.

Currently doing some research on HE fire effectiveness against anti-tank guns, where existing system in CMBO seems to allow somewhat quick end to guns on first few shots against them. If an ATG is dug in and spotted at 600m, a 75mm or 105mm tank weapon with a 30m long HE impact area (1% to 100% lethality probability within area) would theoretically have about an 8% chance of landing the first shot close enough to do something (25% average range estimation error on first try). Came across British "lethal area" sizes for various guns which seem small for 1%-100%, especially for direct fire rounds striking ground at low angles and fairly high velocities (over 1600 fps). Does anyone have definition of British "lethal area" or a source for HE blast drawings applicable to direct fire weapons. ========================================== Recently came across an interesting site on British artillery that is aimed at a broad spectrum of users. Site name is BRITISH ARTILLERY IN WW II and was put together by Nigel Evans. Address is: http://members.tripod.com/~nigelef/index.htm One of the neat items is a system to calculate the number of rounds needed to impact a given number of troops using area fire, which is based on the 25 pdr HE impact. Conversion factors for Russian, British, German and American artillery rounds. Different levels of impact are associated with different numbers of rounds, and terrain and target posture are considered. There is considerable discussion of the model limitations and adjustments that need to be made for the various factors that influence artillery effectiveness. The Russian 122mm and 152mm HE fragmentation rounds are equivalent to 2.2 and 2.8 times the 25 pdr effect, while German 105mm and 150mm HE have multiplying factors of 1.3 and 2.8. Section on EFFECTS AND WEIGHT OF FIRE can be found at: http://members.tripod.com/~nigelef/wt_of_fire.htm The site has many different sections which deal with artillery accuracy, communications and other aspects of the artillery issue, and may prove valuable on several different levels.

Some time ago a generous fellow e-mailed me three pages from a U.S. handbook that included some interesting info about American smoke rounds. The following info answers some of the questions I have been raising on various sites (source of text and drawings has been lost, and would appreciate reference if fellow who sent material reads this): HC SMOKE SHELLS (Base Emission) Shell is used by bouncing it off the ground about 100 to 300 yards away from intended aim point (ricochet fire), useful range is 850 to 1600 yards. Paraphrasing the text: Single tank use of smoke is not going to be effective, it takes a section or entire platoon to smoke a small area. "The section or platoon fires three or four rounds per gun in about one and one-half minutes to screen a suspected area. It takes one to two minutes to build a good screen." The text mentions that tanks generally carry a small load of smoke rounds, and smoke application should be left to tank battalion assault guns and mortars Based on the above, smoke is not going to help much against Panthers at 500m unless one can land a shell on the turret front that stays put. Firing smoke rounds at a Panther or Tiger for one to two minutes would certainly leave one open to quite a few rounds in return before the smoke screen really reduced Sherman vulnerability. The reason for the ricochet range to target, and 850-1600 yards useful range, is not clear. Does the smoke effect take place after the round comes to a stop? WHITE PHOSPHORUS SMOKE SHELL Paraphrasing text: Less screening effect than HC shell due to pillar effect, but "produces an immediate screen on impact, causes wounds and starts fires". White phosphorus would seem to be effective for screening at any range, and might be more effective at close range due to less random scatter along the line of fire. The above suggests that a white phosphorus round fired at the ground in front of a Tiger II might still not block the view needed for a return shot if the pillar is not precisely placed or a gust comes along. The drawings show white phosphorus rounds being used to drive German soldiers out of trenches, pillboxes, bunkers, anti-tank gun emplacements and other defensive positions. GENERAL NOTES ON SMOKE ROUND USE "Smoke is most effective at dawn or dusk on open terrain, in overcast weather and in steady low velocity winds" "A cross wind of from three to six miles per hous is ideal. When the wind velocity is high (15 mph), the rate of fire must be faster than in a slow wind. A wind blowing toward the enemy is desirable during an attack since the smoke blows over the hostile rear areas, blinding the supporting weapons." The above suggests that firing smoke on a bright sunny day will be less effective than dark day use. ===================================== From a wargame viewpoint, Advanced Squad Leader treated smoke rounds as line of sight impediments that reduced hit probability but did not eliminate the chance, and effective smoke application was far from a certainty.

U.S. metallurgical analysis of IS-2 armor found in Berlin ruins discovered that hits on turret would probably crack the turret ring, disabling the tank. There were problems with the armor production. T34 and KV-I armor analyzed by Allies had problems. On other hand, Allies put out how many 56 degree glacis Shermans with armor that was famous for the types of flaws and brittleness it could contain. Russian Battlefield has analysis of T34 and KV-I where 76.2mm round penetrates Sherman front at 1100 meters and American engineers say nasty things about Sherman armor. Armor goes bad for many reasons.

The IS-2 development article on the Russian Battlefield site has info on how brittle IS-2 armor initially was. Tests with 76.2mm ammo at 500 to 600 meters resulted in IS-2 armor penetrations at all angles, and while only a few rounds went completely through, most created lethal fragments inside the turret. So serious armor problems continued throughout the war even if they were not continuous. If Russia used their skilled steelworkers to fill out the army, it is possible those left behind to make the tanks may have less skill and make more mistakes. T34 is high hardness armor, which will fragment more on the inside than a Sherman. One of the interviews with Russian vets discusses how glancing hits on T34 were more dangerous than against Shermans. Stalin supposedly made a statement that poor quality tanks were okay cause the life of a tank was short anyway (and most kills came on side armor hits, where armor quality has little impact on survival). There is another story, put forth by John Waters some time ago (I believer), where IS-3 tanks were running over a cross country course during tests and the weld line on the glacis front broke open. Quality can be elusive.

The question you ask was answered by Vasiliy Fofanov some time ago on the Yahoo!Tankers forum as to BR-365. Early war BR-365 was uncapped AP as shown in drawing, later war BR-365 was APBC is how Vasiliy addressed the issue. My book gives the source of the drawings on the second page of the special note which follows page 63. Source is given as UXO IS book, U.S. Army/National Guard Ground Intelligence center.

I have read where T34 turret seats were stationary, and as turret rotated crew had to get off the seat and move.

Untrue. All 76mm armed T34 had two man turrets. T34 M43 hexagonal turret was bigger, which might allow for more efficiency and a higher rate of fire (more elbow room). T34 was well known for awful vision to sides and rear prior to implementation of a cupola. Little slits in turret side walls often had bubbles in them and were not magnifying glass.

British report WO 291/491 presents comparative dispersion data for British 3" and German 8cm mortar rounds. Ground dispersion of German 8cm was about 2/3 of the 3" figure. Based on the data, German 8cm mortar would range onto targets faster than British 3" and drop a higher percentage of effective rounds. More data from report is posted on John Salt site for weapons effectiveness.

There were four different HEAT rounds for 75L24, only one was capable of penetrating T34 front hull and that projectile defeats 115mm of vertical plate while T34 front hull puts up: 45mm thickness x HEAT slope effect (1/cosine(60°)) x resistance factor based on hardness. A graph in one of Ogorkiewicz's books gave data on effective thickness of armor hardnesses against HEAT, and harder armor makes plate more resistant to HEAT. For T34 high hardness armor the increase is about 8%, so T34 front hull resists like 97mm of vertical plate when hit by HEAT. In a complete turnaround, T34 high hardness armor loses resistance when hit by steel armor piercing rounds due to brittleness, but gains resistance against HEAT cause brittle behavior does not play a role, only hardness. Hardness, as measured by standard tests where a ball is driven into the plate and hardness depends upon indentation depth and diameter, really is the force that binds molecules together and makes them difficult to move (or tear apart). So the harder the steel the more resistance to melting by shaped charges.

Paul Lakowski noted on Russian Battlefield site that 155mm round dropping at 70 degree angle from horizon has 10 times the effective blast area of the same round at 10 degrees, due to sensitivity of fragment spread to impact angle.

The mortar is often described as one of the primary casualty makers of WW II, and TM9-1907 suggests that mortar effectiveness may be underestimated if one goes on the basis of shell size alone. Comparing the 1 hit-per-10 square feet blast area drawings for an 81mm mortar (M56 shell) and direct fire 155mm M107 HE shells after ground contact detonation, the mortar covers more ground with lethal fragments. When a Sherman 75mm HE round detonates 30' in the air, the 81mm mortar round covers about 3 times the area with lethal fragments (1 hit-in-10 square feet), which seems remarkable. While the above results seem surprising, consideration of blast direction suggests that the drawings may make sense when contact angle is considered. When 155mm HE rounds quick fuze detonate on direct fire attempts or Sherman shells detonate in the air, the majority of the fragments appear to be thrown out at an angle that is close to being perpendicular to the shell sides. Pieces that are driven down or up (the majority) from the 155mm ground blast would not pose much of a threat to low level soldiers or equipment, and much of the explosive fragment effect would be lost. On the Sherman air burst, fragments heading upwards or to the sides would be lost against targets close to being under the round. Since a mortar round is coming down almost vertically (about 70° from horizon), fragments that move perpendicular from the sides would form a roughly circular pattern of lethality close to ground level. The percentage of mortar fragments that may potentially strike low level targets in the open would be higher than a 155mm HE direct fire hit or a Sherman 75mm ricochet air burst, making the mortar round more efficient. This is not to say that an 81mm mortar round is the best under all circumstances, since the advantage would be maximum against un-entrenched targets in the open. Against dug-in infantry or bunkers, one would probably want to use ricochet 75mm HE attempts or 105mm direct fire HE. What the above suggests is that HE rounds should probably have different ratings against different target types. Against an infantry attack across a field, the mortar with its high rate of fire and nearly circular fragment pattern might be significantly more effective than an SU 152 or 105mm Sherman (the Su 152 HE round is roughly the same as U.S. 155mm in terms of total and HE filler weight).

Canadian Radley-Walters and his crew killed a ton of Panthers on FRONTAL SHOTS by bouncing rounds off the mantlet bottom and through the hull roof onto the driver or bow machine gunner. He aimed for the exact point needed to precisely get the result he wanted, which was a small area. And he did it with a 75mm armed Sherman!!!!!! Look for The Valour and the Horror web site and there is alot of info on Radley-Walters. I don't have the address after ruining my favorite sites listing. [ April 28, 2002, 07:52 AM: Message edited by: rexford ]

37mm APCBC is a tiny, light round without an HE burster inside, so if it doesn't hit anything vital its presence might be ignored. It might have went in and out of the Puma, making continued Puma use even more possible.

Following looks at 88L56 and 75L48 performance against Sherman "driver plate" (glacis) using data in our booK: If Tiger I is firing on good quality Sherman front glacis hull plate at a 30 degrees side angle, which is what German tables generally look at, the plate is 63.5mm at 47 vertical degrees hit at 30 degrees side angle. So 63.5mm hit at 54 degrees combined angle. T/D ratio is 63.5/88, or 0.72, slope multiplier is 2.33. 63.5 x 2.33 equals 149mm vertical. Tiger 88mm penetrates at 570m. Against Sherman with 50.8mm at 56 degrees driver plate, T/D is 50.8/88 for 0.58 and combined angle on 30 degree side hit is 61 degrees, Slope multiplier is 2.9, so vertical resistance of good armor is 50.8 x 2.9 for 147, which Tiger 88 APCBC penetrates at 650m. If Sherman 56 degree glacis armor is flawed, which is likely, resistance drops by multiplying factor of 0.83 x 147mm for 122mm, which Tiger 88mm APCBC penetrates at 1700m. U.S. did not mandate improved quality control and armor quenching procedures until October 1943, so most 56 degree Shermans had good chance of flaws and 47 degree Shermans tended to be good quality armor. 56 degree glacis Shermans also used multi-piece glacis arrangements with lower resistance cast plates and weld lines. There is a German report which Miles Krogfus shared with us years ago where panzer crewmen indicated that 75L48 could not penetrate 47 degree glacis at 1000m. T/D ratio for 75mm hit on 47 degree glacis is 63.5/75 for 0.85, slope multiplier is 1.86 so 47 degree glacis resists like 118mm vertical, which 75L48 APCBC penetrates at 700m on half the hits. At 1000m, 75L48 penetration is 109mm and penetration probability against 47 degree glacis with no side angle to hit is about 2%. Lorrin

The following site has some interesting material on the Russian 45mm APCR: http://www.geocities.com/Pentagon/Base/1852/57mm.html#29 The interesting paragraph follows: "The tungsten carbide core is surrounded by very toxic mercury chloride HgCl2 or Hg2Cl2. This white to gray substance builds small balls of metallic mercury when heated, it was used to securely fix the hard metal core to the outer shell in the first place. Second, in the moment of impact, these substances change their chemical and thermodynamic properties and act like a liquid lubricant with high density and viscosity under the energetic shock of impact. This helps the core to separate smoothly from the outer shell. The third, and a most welcomed by-effect, is the high toxic nature of the HgCl2 and Hg2Cl2. These are very toxic in their solid property (0,2-0,4g fatal dose), but when they evaporate in the heat as the core is penetrating, they form a very toxic cloud of mercury vapors inside the hit vehicle, killing or severely damaging the health of the crew. If the tank or armored vehicle was not completely destroyed by fragments hitting fuel or ammo, the vehicle could be restored safely after a short period of time, because the mercury vapors disappeared trough the hatches. Remnants of metallic mercury are not too hazardous. Similar Russian hard-core AP projectiles exist from 37mm to bejond 100mm. Because of the very toxic nature of the Mercury- Chloride, one should refraim from opening these shells." I guess a penetration from those tiny 45mm APCR tungsten cores might be more lethal than one would imagine.

When we did the background research for our book, we did not have access to Internet and assumed Russian uncapped AP would penetrate about 10% less than Allied rounds. The 122mm APHE round at 2600 fps would penetrate, by DeMarre from U.S. 75mm M72 AP (solid shot), 257mm if it were exactly the same as M72. Multiply by 0.88 for HE burster in 122mm APHE, for 226mm. Multiply by 0.87 for "quality" relative to M72, to obtain 197mm penetration. Russian Battlefield figures for 122mm AP converted to 50% success result in 173mm penetration at around 2600 fps, 173/226 results in 0.77 "quality" multiplier. Above analysis suggests that Russian AP penetrates about 23% less than Allied AP, after adjustment for HE bursters. Russian projectiles had lower nose and shoulder hardness than Allied uncapped AP, which appears to account for some of the difference. Differences in projectile metallurgy may also be a factor. Interesting aspect of figures on Russian Battlefield, which are similar to those presented by Vasiliy Fofanov on Yahoo!Tankers site, is superior penetration of blunt nose APBC compared to uncapped AP. Russian 122mm uncapped AP penetrates about 173mm at 0m and 0 degrees when data is extrapolated, 122mm APBC penetrates about 206mm under same conditions. Russian Battlefield has a curve where 122mm APBC penetrates over 210mm at point blank See: http://www.battlefield.ru/library/archives/weapons/weapons6.html Russian Battlefield figure for 85mm AP at 0m/0 degrees is about 125mm extrapolated, prediction from 122mm APBC data and curve on Russian Battlefield shows about 144mm for 85mm APBC. The above suggests that APBC could significantly outpenetrate uncapped AP rounds, which is not what we would have expected (standard rule of thumb gives sharp noses better penetration performance at low angle than blunt nose). The "battering ram" appears to be better than the lance, at times, when it comes to defeat of thick armor (and castle doors). Lorrin

You can e-mail me directly and I will provide all the data and equations you will need. Lorrin (Rexford) Bird

Poor performance of 45mm anti-tank guns against 30mm German plates during 1941 can be supported without assumption of ammunition problems or inferior quality. Basic premise, as put forward by Vasiliy Fofanov, is that great majority of 45mm ammunition was uncapped AP rounds. Russian Battlefield presents test data (80%) success for 45mm L46 uncapped AP, which was converted to 50% success criteria against rolled homogeneous armor: 54mm at 100m 40mm at 500m 27mm at 1000m 19mm at 1500m Above data is fairly consistent with DeMarre estimates from Russian Battlefield test data for 85mm, 100mm and 122mm AP at 50% success. It is also worth noting that Russian Battlefield penetration figures for 45mm uncapped AP display a greater drop-off in velocity and penetration with range than predicted by William Juren's ballistic analysis methodology, which is also consistent with information provided by Mr. Fofanov. Penetration against face-hardened armor can be estimated by comparison to other AP rounds, using the Krupp equation, and following figures apply for 45mm L46 uncapped AP: 42mm at 100m 32mm at 500m 23mm at 1000m 17mm at 1500m Above figures are based on standard quality projectile with same metal and nose characteristics as 85mm, 100mm and 122mm AP. Penetration range for 45mm L46 against 30mm/10 degree face-hardened driver plate on PzkPfw IIIG would be exactly 500m if no horizontal side angle exists, and appears to be consistent with combat reports noted by Mr. Fofanov. Following figures apply to uncapped AP fired by 45mm L66 gun: Rolled Homogeneous 60mm at 100m 45mm at 500m 31mm at 1000m 21mm at 1500m Face-Hardened 47mm at 100m 36mm at 500m 26mm at 1000m 19mm at 1500m In view of above analysis, Armor and Gunnery book requires revision to include 45mm uncapped AP if combat against panzers is to be correctly modeled. Numbers provided by Mr. Fofanov suggest that 45mm uncapped AP was primary round for that gun during 1940 and 1941. Information provided on other sites suggests that initial stocks of uncapped AP may have been rapidly depleted as Germans overran ammunition stockpiles or ammo was used. It is not known at this point if ratio of AP to APBC rounds changed as war progressed and Germans overran Russia.

What is the source of the above information? Thanks. Lorrin