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rexford

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  1. The open field hit percentages in mark IV's message seem low, which is the other extreme. At ranges under 500m with the U.S. 76mm, it takes really bad range estimation to miss or an out of alignment gun. Like estimating the target at 340m is at 600m. Were the misses high/low or wide?
  2. Despite Allied combat against Tiger and Panther in Italy, and Soviet notes on their experience, Allied tankers in France seem to have acted as if they were the first to combat the heavy German armor. M10 gunners aimed at the Panther glacis instead of the vulnerable center mantlet area.
  3. In MARK IV's message, were the misses due to targets obscured by woods or were they out in the open. Trying to hit something in the woods where the aiming point may be the center of observed smoke may be alot different from something sitting in the open. Details would be appreciated. Thanks.
  4. At 500m, Sherman vertical height will appear to be 0.053" high to the naked eye. With a 2.4x magnifying gunsight like PzKpfw IVH used, the Sherman profile looks like it is 0.126" high. To maximize accuracy, gunners need to aim close to the vertical center, which is 0.063" above the bottom. That's 1/16 of an inch!! Nervous gunners, bad light, dust or other factors might lead gunners to get off shots at a point removed from the vertical center, which increases number of shots that miss. Later Panther A and all Panther G gunsights had 2.5x/5.0x gunsight magnification, which could double target height observed by gunner and would aid in getting the best accuracy possible. At long range, Panther has smaller dispersion than PzKpfw IV, flatter trajectory and less aim error and better gunsight. At 2500m, Sherman vertical height looks like 1/40 of an inch to PzKpfw IVH gunner. Imagine the difficulty in aiming at the center of something that appears to 1/40 of an inch high, especially if you are thinking that your vehicle may be hit soon by an M36 or aircraft and your hand is shaking slightly and sweat is pouring down your face in a closed down tank in the August sun and powder smoke is in your nostrils and lungs! A Panther D is reported to have hit and knocked out a T34 at over 2500m during the Kursk battle, before the Panther self-destructed. Later JagdPanthers had 10x magnification gunsights! Tiger II may have had 3x/6x. Nashorn had 5x. While Sherman at 2500m looks like it is 1/40 of an inch high to PzKpfw IVH gunner, it looks like 1/10 of an inch high to aiming member of JagdPanther crew. To get maximum accuracy one needs the proper gunsight. Early Shermans used in desert reportedly used gunsight on top of tank instead of coincident with barrel, and connection between gun barrel elevation and gunsight was prone to alignment errors. Early Shermans supposed to be inaccurate due to gunsight alignment problems, as well as poor optics if various sources are to be believed when they say that pre-war world depended on German optical glass, and once war started Allies had to struggle to make decent gunsights.
  5. We recomputed hit probabilities vs. Sherman front after reading earlier responses: PzKpfw IVH/StuG IIIG 75mmL48 APCBC 95% at 300m 93% at 400m 90% at 450m 76% at 500m Panther 75mmL70 APCBC 95% at 400m 93% at 500m 81% at 600m The guns are very different in two respects, Panther 75 has flatter trajectory due to higher speed, so less aim error per range estimate erro. Panther 75 also has considerably less shot-to-shot dispersion for a constant aim. The computed Panther and PzKpfw IV accuracies vs. range are typical by falling suddenly at a given range. Inside 450m or so, PzKpfw IV 75mm should not be significantly less effective than Panther in terms of hit probability, which suggests that alot of PzKpfw IV's in defensive position may be more effective than fewer Panthers if panzers are vulnerable to flanking. PzKpfw IVH may also have higher rate of fire if heavier and longer Panther rounds slowed fire rate Does anyone know if Panther rate of fire was less than PzKpfw IVH? A U.S report estimates 7-8 rounds per minute for Panther, which seems high but Tigers could pump out steel at close to that, at least initially when rounds were easy to grab. 75mmL48 at 450m should consistently kill Sherman front armor even with a 25° angle between hull and firer. 65° angle hits on 38mm Sherman side armor would also go right through, and about half the hull hits at 25° hull angle to PzKpfw IV hit side hull armor. If firefight is less than 500m, PzKpfw IVH may be as lethal as Panther if panzers get first shot. Barkmann's Corner is an Advanced Squad Leader scenario where Barkmann did foot recon to spot oncoming Shermans, ran back to his Panther and then sped out of the woods and fired on Shermans, one after the other, at really close range (Shermans tried to back-out of Panther view but couldn't). If memory serves right, Barkmann got them all, and kept pumping in shots until they burned. Would Barkmann have done this in a PzKpfw IVH that might crash and burn after one Sherman hit? Probably not, so PzKpfw IVH may not always be the best bet and Panther could be superior. There is another story where a Panther in Normandy was being shot at and hit by a Sherman at close range, and the shots kept hitting about the same spot on the glacis and bouncing off. The Panther commander noticed another Sherman trying to flank his tank so the Panther rotated its turret and took out the threatening Sherman while the first Sherman kept bouncing shots off the panzer glacis. Panther commander figured correctly that Sherman was fixated on getting hits and wasn't about to change a thing. American tankers taught to aim at mid-point on vertical tank profile, which is glacis, and at close range shots will bunch about aim point. Some Sherman tanks obviously kept to their teaching exactly as taught even when continued hits in same spot did nothing. Germans aimed at turret/hull meeting point, which meant that half hits struck vulnerable turret, half hull, and aim point hits might disable turret by jamming turret ring or penetrating weak armor. Regarding range estimation errors, Tiger commanders expected to estimate range within 10%, on average, while others tried for 25%, based on German training manuals like Tiger Fibel.
  6. We have been computing shot accuracies based on typical range estimation errors (25% error) and projectile dispersion around aim point, and the results seem technically correct. However, Panthers and PzKpfw IVH's have about 100% hit probability against a fully exposed medium tank inside 500 meter range, which doesn't seem realistic. What has been your experience with medium and short range accuracy in CM, and should a cap be placed on maximum weapon accuracy to model nervous nellies, dust or glare in the eye or a gunner who sneezes at a critical point? What would the cap on max accuracy be? Should all shots hit at 200 meters? At 100 meters? At 500 meters? Never have 100% accuracy? Our calculations seem to be missing something. Thanks.
  7. Who would be attacker and defender? What type of Sherman, 76mm or 75mm? If 76 Shermans, HVAP available? 2 88's suggests Germans on defense,and 10 StuG III might take a big bite out of 17 Shermans unless terrain reduced line of sight of StuG's. We're interested in your scenario and would like more details. Thank you.
  8. U.S. went to HVAP and HEAT after war. APBC was old Russian navy round, and American pride and prejudice during McCarthy years and Red Scare probably wouldn't allow copying a communist ammo type. Naval rounds at long range strike armor at steep angle, and Russians found way to increase effectiveness. Soviets may have hid true penetration of APBC during war by publishing false penetration data that everyone seemed to accept. In desert war when M48 met Stalin III, slow rate of fire of 122mm APBC (1.5 rounds per minute) gave M48's time to bracket Stalin with HEAT and hit on third or fourth shot. First shot long, second short, third and fourth closer and closer. HEAT is slower than other rounds but bracketing improves accuracy.
  9. ACHTUNG! Highly technical stuff follows! We have collected and analyzed firing test and battlefield reports for about 25 years, and have tons of reports from NTIS and other sources that date from WW II. U.S. report on nose hardness effects address shatter gap and penetration increase as nose gets harder. 20mm Test Projectile Velocity Nose at Hardness Complete Penetration* 63.5 Rockwell C 1930 fps 61.5 Rockwell C 2055 fps 56.0 Rockwell C 2185 fps --------------------------- 52.0 Rockwell C 2350 fps (estimated from extrapolated curve, 52 Rockwell C is Soviet ammo hardness from U.S. tests on rounds given to U.S. by Russia during war). German APCBC and APC nose hardnesses were analyzed by British during war, captured rounds,and results follow: 75mm Pak 40 58.5 Rockwell C 75L70 57.5 88L71 60.0 50 APC 61.5 50 APC 61.5 88L71 61.8 75L48 64.0 ------------------ Average = 60.7 U.S. ammo about 56 Rockwell C,a nd British rounds had about the same penetration in tests so we assume effective hardness of British ammo equals U.S. German rounds averaging 60.7 Rockwell C nose hardness should outpenetrate U.S. ammo by about 7%, based on above data for penetration velocity vs. hardness when data is converted to equivalent thickness using DeMarre equation: If it takes softer nose 2030 fps to defeat armor when harder nose does it in 1930 fps, harder nose would penetrate 7.5% [(2030/1930)raised to 1.4283 power] more armor at same velocity. A British table gave 75L70 and 88L56 penetration at 30° versus British plate, which is roughly equivalent to U.S test plate. We converted the figures to 0° penetration using slope effects and T/D ratio and it came to 190mm at 0° and 0m against U.S. quality test plate (3068 fps). U.S. 75mm APCBC weighs the same as 75L70 APCBC but was shot at 2030 fps. Using DeMarre equation, if Panther 75mm was same hardness and quality as U.S. 75mm it would penetrate 91 x[(3068/2030)raised to 1.4283 power], or 164mm at 0°/0m. 190/164 => German ammo about 15.8% better, so it exceeds prediction from U.S. tests with 20mm ammo, which makes sense since using small ammo to predict large stuff is risky. U.S. compared German 75mm penetratin against Sherman 75mm in a test against same plate at same velocity, German rounds penetrated more armor ("somewhat more armor penetrated"). Germans estimate 168mm/0°/0m penetration for 75L70 APCBC, German test plate about 10% stronger than U.S., for 185mm penetration by 75L70 against U.S. plate. If 75L48 APCBC were same quality and hardness as U.S. 75mm, it would penetrate 91 x [(2460/2030]raised to 1.4283 power], or 120mm at 0m/0°. Comparing penetration ranges to penetration and armor data, 75L48 penetration should be more like 139mm at point blank. We have done research on how armor loses effectiveness due to high hardness, casting, flaws and have various graphs that are based on the T/D ratio and other factors. The above analysis is speculative in nature but we try to support estimates and conclusions by cross-checking penetration range reports and other sources. The research also picked up on some unusual tank, armor and projectile characteristics, such as: Panther A and D used face-hardened armor on front lower hull and side hull armor (upper and lower), which increased vulnerability to APCBC and APC, although front nose could only be penetrated a short distance by 76mm APCBC. Panther D glacis was face-hardened, based on data we've seen. T34 used high hardness armor and lost 24% of resistance when hit by 75mm APCBC. Published data for Soviet AP and APBC is based on face-hardened penetration figures, and may not represent what ammo was capable of. Russian APBC had unbelievable effectiveness against sloped armor due to flat nose. Pointed noses may bend when sloped armor is hit, and since rounds penetrate sloped armor by going thru hole in downward direction for upward armor slope, noses tend to get in way and retard penetration as they bang against sides of hole. Sloped armor is defeated by driving a plug of armor out of the material, the round then slips through the opening. 122mm AP penetrated Panther mantlet to 700m in combat, 122mm APBC penetrated beyond 2500m due to ballistic cap and superior performance against sloped armor.Valera Potapov has a big article on IS-2 and IS-2m at http://military.virtualave.net/is2_1.html See British report PENETRATION OF ARMOUR PLATE for more on flat head ammo, how rounds penetrate sloped armor, shatter gap and other topics. The report indicates that shatter gap with 2 pounder AP occurred at less than 2600 fps. Since 76mm APCBC shatter failed against Tiger front beyond 300 yards and was fired at 2600 fps, this suggests that capped rounds do suffer from shatter gap and at velocities below 2600 fps. Uneven resistance of Panther glacis against repeated hits by same round at same range due to flaws. At Isigny, France, Allied test firing during August 1944 showed that 2 of 3 Panther glacis cracked after defeating hits due to flaws and brittle behavior, follow-up hits near cracks penetrated. U.S. armor prior to October 1943 prone to flaws.
  10. Robert Livingston found a scaled drawing of the Tiger I mantlet in Culver and Feist Tiger I, with the OKH mark (Wa Pruf 6). His figures are based on that drawing. Later Tiger mantlets added 35mm around holes to bolster openings. Figure around 140mm minimum resistance on any area.
  11. American and British rounds with armor piercing caps also shattered,and at velocities below 2600 fps. British 2 pounder AP shattered below 2600 fps. The published research does not appear to tell the whole story.
  12. Cast armor is weaker than rolled because rolling armor changes the structure and gives it better impact resistance. Thick castings absorb impact better so they are less inferior to rolled armor, lots of material spreads the impact around. Cast inferiority is function of T/D ratio, where T is cast thickness and D is steel projectile diameter. Panther mantlet is cast, Tiger mantlet is cast, M4A1 hull is cast, Shermans have cast nose armor and 56° glacis Shermans have about half cast armor on glacis. Sherman and Pershing turret is cast. Pershing hull may be cast. When 80mm thick Pershing cast glacis is hit by 88mm L71 APCBC from Nashorn, it will be about 10% less resistant than rolled armor. Tiger mantlet is so thick that it is not very different from rolled armor when it is hit by 76mm APCBC or 90mm APCBC, maybe 1% less resistant for 140mm thickness.
  13. U.S. penetration data for WW II ammo is documented in TM 9-1900, providing penetration data at angles from 0° to 75°. Data for each projectile may provide different angles beyond 0°, and homogeneous and face-hardened armor are treated. Using 37 APCBC data from TM 9-1900 the following ranges would apply for 50% penetration success when a Stuart or 37mm anti-tank gun directly fires on the front of PzKpfw IVH: Cupola : none Turret front: 1500m Driver plate: 50m Glacis : none Nose : none One problem with Marder and Nashorn is that their gun sight has an 8° field of view, compared to 25° for PzKpfw IVH and 28° for Panther. StuG IIIG, JgPz IV, Elefant and Jagd Panther also had about 8° gun sight viewing. Limited gunsight fields might hurt when moving targets have to be tracked at close range. By the time the gun is rotated onto the target the target has moved out of the gunners sight. Best to set up those self-propelled and anti-tank vehicles so the guns cover likely approach avenues. Sight data also suggests that turretless guns may be best used for medium and long range fire. Regarding turret rotation speeds, Tiger and Panther are generally pointted out as slow spinners, but PzKpfw IVH and IVJ are even worse: TURRET ROTATION TANK SPEED Panther 20°/sec. high speed rotation Panther 12°/sec. U.S. tests in Europe Tiger I,II 18°/sec. high speed rotation Tiger I 6°/sec. test data for 1 tank Sherman 24°/sec. PzKpfw IVH 14°/sec. PzKpfw IVJ 7°/sec.
  14. An article by Robert Livingston in AFV NEWS several years ago pointed out that Tiger I mantley was actually thicker than most publications listed. A drawing by Livingston showed that Tiger I mantlet was 140mm to 145mm thick through most of mantlet, 175mm over sight holes and 97mm to 127mm on upper and lower edges but backed by 100 turret front bar. 110mm left and right edges were backed by turret side wall. A hull down Tiger I would be a most difficult target for 76mm APCBC, a point that has been noted in several books.
  15. Shatter gap is documented in U.S. tests on projectile nose hardness effects, where harder noses penetrated more armor. German ammo was harder than others, and in U.S. tests 75mm Pak round out-penetrated U.S. 75mm from Sherman at same velocity and weight. U.S. penetration data from Naval sources also documents shatter gap failure. It is called a shatter gap because the round penetrates, then it fails, then it penetrates again, as velocity increases. The definition of penetration data also works to panzer benefit. When penetration equals armor resistance, half the hits succeed and half fail. This is U.S. Navy Ballistic Limit. When 75mm APCBC ammo from Sherman exactly matches driver plate on PzKpfw IVH, 50% survival rate. To obtain 100% penetration success rounds have to exceed armor resistance by at least 10%, which is in middle of shatter gap region. British put armor piercing caps on their solid shot to reduce shatter gap tendencies, which they were forced to acknowledge in North Africa. British tests with best quality ammo showed that armor piercing caps reduced shatter gap effect to almost zero. However, British firing tests against captured Tiger with various of their APCBC resulted in shatter failures where penetration should have occurred.
  16. Marders and PzKpfw IVH's are the equal of Panther at close range when it comes to penetrating Shermans and M10's, and lots of tinny panzers may have been needed to stop lots of Shermans. 10 Shermans trying to flank 7 PzKpfw IVH's in defensive positions is more difficult than 10 Shermans against 2 Panthers. Panzers benefitted from two factors that are little known but significant. When penetration exceeds effective armor resistance by 5% to 25%, above 25% hits succeed due to momentum. Projectile nose may shatter in 5% to 25% excess penetration range and hit may fail. This is referred to as shatter gap. Shatter gap occurs because back pressure on nose exceeds allowable limits for lower nose hardnesses used by Americans, British and Soviets. When penetration equals armor resistance, half of the hits succeed and there will be certain back pressure due to movement of armor material. When penetration reaches 5% above armor resistance, back pressure causes shatter fail which continues until penetration exceeds armor resistance by 25%. Then pieces and fragments start to penetrate again. 75mm APCBC from Sherman will shatter fail against PzKpfw IVH driver plate out to 300m, and then will penetrate. So at close bocage ranges 75mm APCBC from Sherman fails to penetrate 80mm driver plate on StuG and PzKpfw IVH. Some penetrations might occur when nose hardness exceeds shatter gap area, since actual projectile hardnesses in field would vary from design value. 76mm APCBC from M10 and Sherman should penetrate Tiger driver plate at 1000m, however, in France it was reported that hits failed beyond 300 yards. Blame it on shatter gap. British reported on shatter gap in North Africa, where 2 pounder would penetrate out to a certain range, then would fail over some distance,and then would penetrate again. Or 2 pounder would fail to penetrate at close range and then penetrate further out. German ammo nose hardness was usually above the shatter gap region. The other factor favoring panzers is that at close range hits tend to bunch around the aim point, which is often right in the mid section of the upper hull front or glacis. We calculated that range estimation errors and shot-to-shot dispersion would result in the following % of turret hits when M10 fired on the front of a Panther: 100m 2.5% of hits on turret 200m 12.5% of hits on turret 300m 25% of hits on turret When these close range hits strike the turret they tend to land on the lower areas and avoid the vulnerable mantlet center which is almost vertical. The 899th Tank Destroyer Bn reported on initial battles with Panther in Normandy, using M10. No penetrations of Panther front armor occurred, a few penetrations occurred through MG port and a few hitson mantlet bounced through hull top armor. This supports the concepts presented in this message. Unusual phenomena came to the aid of the panzers.
  17. <BLOCKQUOTE>quote:</font><HR>Originally posted by Big Time Software: We are planning on adding some vehicles in the future. FYI we have a VERY nice looking set of Sturmtiger pics (how all models start out!), but there are way too many other things on the list ahead of it. The most oddball, rare vehicle that will be in CM is the M26 Pershing. We just put the rough model and texture set Sunday. Just watched it duke it out with a Nashorn. Hint... if the Nashorn gets off the first shot on the flank, the Pershing can just forget about getting off a shot! But it is funny to see 88s bounce off the front. Damn fine tank! And if you have about $160k and a very big garage, I know where you can buy one too Steve<HR></BLOCKQUOTE> Observations: Nashorn 88mmL71 should be able to penetrate Pershing glacis plate out to 2000m. Pershing hull front is cast armor, which is less resistant than rolled armor. Pershing round mantlet is 113mm cast, 88mmL71 might find this fairly easy pickens on a high percentage of mantlet hits. There was a Super Pershing that had a Panther glacis plate fixed to the frontal armor and the Super Pershing used an extra long 90mm gun. According to Hunnicutt's Pershing, it looked for but never found a Tiger II for a joust.
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