rexford

Mr. Tittles asked: "These 75mmL48 APCBC rounds carry 83 grams or so of HE. I HIGHLY doubt that the detonation of this HE in the back of a hardened AP shell would shatter it beyond the very small cavity area (if that). What is your source of a Sherman AP round having over a pound of HE?" Accidentally quoted the weight of HE in an HE shell. 1.7 pounds is 75mm Sherman HE. Regardless of what you doubt or think, British and Russian tests showed that when 75mm APCBC-HE and Russian 122mm APHE penetrated the 20mm spaced plate on the PzKpfw III the HE burster in the round detonated before it reached the 50mm main armor, and the hit was defeated. The British showed that the defeat was due to the HE burster detonation because when they took out the HE and replaced it with an inert filler, the rounds penetrated the 20mm spaced plate and the 50mm main armor. So what was left of the projectile, in terms of fragments and pieces, did not have enough penetration left to get through a 50mm face-hardened plate a few inches beyond the detonation. Sounds like the round was fairly damaged if it failed against a 50mm plate. [ June 27, 2004, 03:07 PM: Message edited by: rexford ]

Both conditions cause an impact which may set off the HE burster. Why don't you do a research project with regard to whether bouncing an APCBC-HE round off the ground will set off the burster, and get back to us.

Interesting that we're talking about the Tiger mantlet and the picture refers to the 100mm front hull plates. Most defeated hits will not lodge in the armor, the penetration has to be very very close to the effective armor resistance for a lodged hit, which doesn't occur very often. Yes, a lodged round may do all sorts of things to the crew inside a tank, but no with regard to a lodged hit being the normal defeat mode.

I read a few books on the Tiger which described the impact of repeated hits by 57mm and 76mm ammo on the hull, where the shaking broke equipment free from attachments on the wall. In one case, a 76mm hit on the 102mm thick driver plate pushed the plate in far enough to hit the driver on the head and kill him. A 135mm-197mm ductile casting is going to absorb more of the hit impact energy, and cause the projectile to self-absorb more of the impact energy, than a 102mm front or 80mm side plate. Remember that as the resistance of the armor increases above the penetration of the round, more of the impact energy is used up in self-destruction of the projectile. When 37mm and 50mm rounds hit the KV-I and KV-II armor during the early battles of 1941, the rounds would bounce off the armor and the only mark would be some damage to the paint. Very little impact energy was absorbed by the tank armor. It's similar to hitting a thick wall with a hammer, the hammer bounces and does not leave much of a scar because the thick armor spreads the impact out over an immense area. The impact energy of the hammer is converted to rebound energy.

Not true, sir, on all points. The 90mm APCBC_HE was prone to detonating upon contact. The 75mm APCBC-HE worked just fine in the British tests and exploded between the plates. You also disregarded my reference to Russian tests where the 122mm APHE round detonated between the 20mm spaced plate and the 50mm main armor. I did not attempt to use the 75mm Sherman APHE round as a benchmark but presented two completely different projectiles. A 20mm plate is nothing to a 75mm APCBC round, whereas hitting the ground radically changes the flight path. The 75mm Sherman APCBC round carries 1.7 POUNDS of high explosive, which would seem to be enough to rip the round apart. That is the purpose of HE fillers in armor piercing rounds, to turn the ammo into a grenade that explodes in the tank and send fragments flying about.

Forgot the Churchill VII. Alot of heavy mantlet hits would have the potential to break things through vibration, and misalign critical components. But 135mm to 197mm of good cast armor can take quite a few hits with minimal problems.

While the Tiger is a 1942 tank, the mantlet armor would not be matched or exceeded by very many turreted tanks during the war. The Tiger mantlet ranges in effective thickness from 135mm to 197mm (while the minimum thickness is 97mm on the upper and lower edges, that armor is backed up by a spaced 100mm armor area), and is only exceeded by: King Tiger Jumbo Sherman Super Pershing The Tiger mantlet armor was high quality cast material that was capable of taking extensive punishment without severe cracking, and the castings resisted penetration like rolled armor due to the thickness. There are pictures of Tigers with 122mm rounds stuck in the mantlet, which suggests good armor toughness. IS-2 has a 110mm mantlet and 100mm turret front, Panther has a 100m mantlet. U.S. 76mm armed Shermans have 89mm mantlets. Even the standard, late war Pershings don't have as thick a mantlet. The Tiger mantlet is capable of stopping hits from U.S. 76mm APCBC and Russian 85mm AP or APBC at just about any range, and it takes the U.S. 90mm or Russian 122mm or 100mm to really score a kill with one hit. A hulldown Tiger is a difficult target for most tanks and SPG right up to the end of the war. [ June 26, 2004, 10:26 PM: Message edited by: rexford ]

If a 20mm spaced plate on the front of the PzKpfw III will detonate the HE burster on a 75mm Sherman round before the round reaches the main armor, and will do the same to the 122mm AP, it does not take much to set off the burster. There are a few inches between the spaced 20mm plate and the 50mm main armor on PzKpfw III, so AP rounds with HE bursters don't last long after the initial impact. In British firing tests, the Sherman 75mm APCBC-HE hits the PzKPfw III spaced 20mm plate at about 100 yards, say 2000 fps. It takes very little energy to pierce a 20mm hard plate at 30 degrees, say 822 fps. Which means the round leaves the 20mm plate going 1823 fps. There is about a 6" space before the round hits the main armor, so the time for the burster detonation is less than 0.5'/1823 fps, or 0.00027 seconds. Not a whole lot of time. [ June 26, 2004, 10:06 PM: Message edited by: rexford ]

The final adjustment to the range estimate brings the shot placement from the target contact with ground to the approximate midpoint, and is accomplished by measuring the height of the observed target in mils (using the gunsight triangles), and then adding twice that number times 100m. If a tank target was 3 mils high on the gun sight, half would be 1.5 and the adjustment would be an addition of 150m. If a Tiger was firing on a hulldown T34 and the turret appeared to be 0.50 mils high, the range would be estimated and the modified by an addition of 0.50 x 1/2 x 100m or 25m. I did some ballistic studies using a trajectory computer program and the method works very well. The Tiger crew would not have to remember an equation for the final adjustment, they would measure the approximate height on the sight and add half the height times 100m.

Good points. The Tiger Fibel does not say what to do if the target is hull down, or behind cover. The only instructions are for fully viewable targets, as far as I can see.

The German procedure was to set up the gun sight on the bottom of the observed target, estimate the range, and then increase the range by a certain amount so the shot would be aimed at the target middle (give or take). If the estimated range were 500m, the addition would equal 100m x (1000m/500m) or 200m, so the gun would be elevated for a 700m shot against the target bottom. This would place the shot near the target center if the initial range estimate were correct or very close. In the case brought up by MikeyD regarding a Tiger and Sherman coming face to face, perhaps the commander ordered the gunner to fire at 100m range and forgot to add the modifier (100m x 1000m/100m or a 1000m + 100m shot). It is possible that a 100m shot would bounce short, although it is hard to see why a near miss would raise the Sherman off the ground. Would an 88mm HE near miss cause a Sherman to rise off the ground? [ June 25, 2004, 04:50 PM: Message edited by: rexford ]

If a Tiger uses battle sight aim against a 2m high target at 500m it will miss quite a bit. Seeing something that close the Tiger would probably just assume a 500m range and aim for a 700m shot against the target bottom, which would bring the shot up near the middle.

JasonC said with regard to my past posts: "Anything that might endanger his beloved Tigers from the side he would resist with the greatest imaginable tower of fudge." The Tiger side and rear armor plates resisted penetration like 84.5mm average effectiveness during British, American and Russian firing tests, with a standard deviation of about 7%. So the Sherman 75mm APCBC would penetrate the 84.5mm average resistance on 31% of the perpendicular hits at 500m, and 14% at 750m. In British tests the Sherman 75mm APCBC penetrated the Tiger side armor at 800 yards, and in other tests the rounds failed at 500 yards. That's why an average is important, with a statistical standard deviation. CMBO undermodels the Tiger armor resistance by overestimating Sherman 75mm APCBC penetration (89mm at 500m instead of 81mm), only gives the Tiger 80mm side thickness (should be 81mm to 82mm), and does not model the better armor (which combines with above-design thicknesses to resist with an average resistance of 84.5mm). I don't like the way Tigers are easily penetrated in CMBO so I don't use em. Simple response. I don't expect CMBO to change and live with what is. Russian tests showed the T34 76.2mm APBC bouncing off the Tiger side armor at 200m with terrible damage to the projectiles. As I've stated many times in the past, the Russians had uncapped solid shot AP rounds designed to penetrate the Tiger side armor and super hard BR-350B APBC designed for Tiger bashing. Penetrations against Tiger II armor cannot be compared to 1943 hits on Tigers and StuG IIIG because different ammo could be in use. [ June 20, 2004, 03:03 PM: Message edited by: rexford ]

The Sherman 75mm APCBC penetrates 95mm face-hardened at 500m, so should be able to defeat the StuG III driver plate and the 50mm/51 degrees upper superstructure front beyond 500m.

The Russians did not use armor piercing caps during WW II, and if JasonC suggested they did he is wrong.

The previous accuracy figures for a 1000m aim at the observed target bottom were for a 2m high target flush with the ground. Against a 2m high T34 with 0.4m ground clearance the accuracy figures for 1000m aim at target bottom would change significantly: Target Range/hit % 100m/76% 200m/94% 300m/84% 400m/66% 500m/58% 600m/63% 700m/79% 800m/93% 900m/81% 1000m/23% Aiming at the ground level where the tracks touch raises the tank profile so the maximum trajectory height of 2.3m is slightly below the maximum tank elevation. Given the complexity involved in estimating first shot target range the use of battlesight aim would speed things up and increase the hit percentage against targets beyond 500m.

Face-hardened armor is damaged when it defeats hits, and 30mm/30mm or 30mm/50mm combinations are a maintenance headache. That's why the combo armor layouts were eventually replaced with a single plate fo 50mm or 80mm thickness. The Tiger was intended to drive into enemy positions and take tons of punishment from all sorts of guns, something that face-hardened armor would not stand up to for long. The PzKpfw IIIH and IVG situation vs Tiger is similar to the T34 vs KV-I. The T34 carried very high hardness armor that did not stand up well against large caliber hits, even if they did not penetrate. The KV-I was meant to engage in slugfests and take repeated hits, so it used armor hardnesses similar to Tiger.

JasonC stated: "Rexford knows a lot of data. But honestly trying to get at a truthful picture he is not. Anything that might endanger his beloved Tigers from the side he would resist with the greatest imaginable tower of fudge." British tests against PzKpfw IIIH showed that 30mm/30mm resisted like 69mm when all the plates are face-hardened. U.S. tests against PzKpfw IV 30mm/50mm showed that it resisted like more than 80mm with all plates face-hardened. Instead of presenting firing test data that refutes the above tests, JasonC resorts to the above nonsense. Really very silly stuff, Jason. And he is so confused. PzKpfw IIIH and PzKpfw IV carried face-hardened armor on the front, the Tiger did not use any face-hardened armor at all. There is nothing in common between T34 penetrations against face-hardened layered plates and the side armor on the Tiger. Jason, please try to argue logically and refrain from bad mouthing my efforts. Okay?

Two additional points: 1. the gunner's range estimate is given twice the weight of the commander's and driver's, which probably acknowledges the benefits of using triangles to improve the estimate. 2. after the range estimate is made, the commander must do some mental gymnastics to increase the range because the gun is aimed at the bottom of the target and an addition must be made to put the shot higher up on the target. This further complicates the range estimating process for the first shot at a target, extending the time and opening the door for possible math errors.

The 50mm Pak APC round should penetrate about 100mm at 0m and 0 degrees (homogeneous armor), while the Stuart 37mm APCBC round should penetrate about 80mm. The Stuart round is solid shot which gives it a small bonus compared to the 50mm PaK which contains a shell weakening HE cavity. The T34 76.2mm APBC slightly outpenetrates the Stuart 37mm APCBC at point blank against face-hardened and homogeneous armor. There was an uncapped Stuart 37mm AP round that penetrated about 94mm homogeneous at point blank.

"The myth that the Tiger was invincible has now been exploded." Interesting that British troops held such an opinion, since 6 pdr anti-tank guns in North Africa had knocked out one of the first Tigers met in combat. Experiences in Italy and Tunisia probably resulted in the feeling that Tigers were impossible to knock out. The most recent experience is sometimes the one that sticks in the mind even though a little research disproves the opinion.

The basic BR-350, BR-350A and Br-350B APBC rounds are all similar in shape (flat nose) and nose hardness, and they do not have an armor piercing cap. They have a ballistic cap which is a thin collapsible wind screen to reduce air resistance. American 75mm APCBC penetrates 95mm face-hardened at 500m while BR-350B penetrates about 83mm of the same armor at 0m. The difference is due to: 1. American 75mm APCBC is at 54.5 Rockwell C nose hardness, Russian 76.2mm APBC is at 50 Rockwell C. Softer rounds penetrate less. 2. American APCBC has an armor piercing cap which protects the nose from the damaging effects of face-hardened armor, while Russian 76.2mm APBC does not have an armor piercing cap. Face-hardened armor depends upon significant damage to the projectile nose to defeat hits, that's how it works. Anything that protects the ammo from break-up or shatter increases the penetration of face-hardened armor. Homogeneous armor depends upon energy absorption to stop hits, that's why the armor is softer than face-hardened so rounds can partially penetrate and use energy pushing armor out of the way. An armor piercing cap uses up more energy penetrating homogeneous armor than it contributes, and that's why the Sherman 75mm APCBC penetrates 82mm homogeneous at 500m and 95mm face-hardened. The Russians did not use armor piercing caps during WW II. During late 1943, the Russians super hardened the BR-350B rounds and increased the penetration by about 10%. Limited production. Probably not in CMBB. The Russians also made 76.2mm solid shot with a pointy nose, which was designed to penetrate the Tiger side armor. Limited production, and probably doesn't show up in CMBB. CMBB does not present both homogeneous and face-hardened armor penetration stats for guns, which can be confusing.

Originally posted by c3k: "I've repeatedly argued/held that the wonderful game modelling by BF.C consistently falls short in the realm of sights. It seems that the in-depth optics knowledge by a BF.C member has somewhat blinded them to the large advantage to be gained by different reticles and sights." The Germans seemed to have done alot of things right, and the Americans appear to have suffered through a period of goofs and corrections. The Sherman gunnery tech manual acknowledges that the early Sherman sighting system, with a periscope atop the turret, was prone to misalignment which would ruin or at least inhibit hit chances. "The German method of adjusting the gun so the sight is always centered on the target seems better than the allied method of adjusting the sight to the target." It does seem easier to aim at the middle of the target, or any other special area, when the cross hairs stay in one place. "(A note on your accuracy tables: I certainly cannot argue with any of the figures, however, the high miss-rate at low ranges may be misleading. In sub-800 meter engagements, I would expect the range estimates to be pretty close (10% to 50% would still produce more hits). The 1,000 meter range preset would be advantageous in situations where the range is not so obvious, would it not?)" The accuracy tables were based on the 1000m aim at target bottom, and it probably would not take long for a Tiger crew to realize something was wrong with the graph. Since the Tiger crews tended to be elite and hand picked, especially in the earlier periods, seeing a target at 500m would probably result in the use of the visual range estimate method since 500m is not that far. Your comment is correct though, at 400m to 600m the range estimate errors would probably be small. "Thanks, Ken" Thank you for the response.

By basing the visual range estimate on an averaging system, the Tiger would gain over vehicles and tanks that used a single crewmen's estimate. Using an average range estimate error of 25%, which is consistent with British trials and tests conducted by our group, the following summarizes the impact of averaging the range estimates of one, two and three men on 1000m targets: 1 man: 25% average error 2 men: 17.2% average error 3 men: 15.1% average error The data was generated by assuming a bell shaped distribution and running 100 trials allowing random range estimates. In terms of first shot hit probability at 1000m against a 2m high x 2.5m target, the range estimates would result in: 1 man estimate: 25% hit chance 2 men with average of estimates: 35% hit chance 3 men with average of estimates: 40% hit chance Everything else being equal, the Tiger Fibel method of estimating range would result in a 60% higher first shot hit chance over a one man prediction. The advantage would be somewhat higher if the Tiger gunner used the triangles to estimate range based on the observed target size.

TIGER FIBEL NOTES ON WEAPON ACCURACY AND USE The Tiger Fibel presents a wealth of information about the gunnery procedures used by Tiger crews, and the following notes discuss the Fibel guidance relative to 88L56 APCBC accuracy (the Tiger Fibel is available on line at http://tiger1.info/fibel/). The Fibel material is also compared to the instructions in ARMORED FORCE FIELD MANUAL (Tank Gunnery) , April 22, 1943, for 75mm armed Shermans as a means of showing relative strengths and weaknesses. 1. GUN SIGHT RANGE MARKINGS: Page 66 in the Fibel The Tiger sight fixes the top point of a triangle against the intended aim point, and the circular range dial slides by an arrow as the gun is elevated. Ranges are marked in 100m increments. In comparison, the Sherman gun sight has range markings in yards at 0, 600, 1000, 1500, 2000, etc.. The Tiger sight would seem to promote greater accuracy due to less guesswork on range settings. 2. RANGE FINDING USING PERCEIVED WIDTH OR HEIGHT: Pages 67, 70 and 88 in Fibel A line of triangles on the Tiger gun sight define 4 mil increments of lateral angle, and 2 to 4 mils of vertical angle (1 mil of arc creates a 1m wide pie slice at 1000m range). The triangles can be used to estimate range since the 3m front width of a T34 will appear 3 mils wide at 1000m, 1.5 mils at 2000m, 4 mils at 750m, 6 mils at 500m, etc., and the 6m side will appear twice as wide at those ranges. The Sherman manual notes that the coaxial machine gun can be used to estimate range by rolling shots onto the target starting from the initial range estimate. While the ranging coax machine gun method may work it could also give the Sherman position away, as could the other ranging method where one tank in the platoon opens fire and the rest join in after the range is determined from a hit. The triangle method for range estimation would work, though not with high precision, against the 6m side of a T34 even if the firing weapon were angled at 0 to 65 degrees from the armor facing. 3. VISUAL RANGE ESTIMATION: Page 69 in the Fibel For Tiger crews, visual range estimation for the first shot at a target is a group effort where the commander (panzerfuhrer), driver (fahrer) and gunner (richtschutze) each estimate target range and the commander averages the figures. The use of three independent range estimates may provide some advantages over the Sherman in terms of improved accuracy, where the Sherman commander alone provides the initial weapon range. With practice one might expect the Tiger averaging process to proceed without unusual delay, although some Russian reports note that Tigers were often slow to fire. The range estimates used in the Fibel example suggest that individual Tiger crewmen were not expected to estimate target range to within 10% of actual, as has been suggested in some references. 4. BATTLE SIGHT AIM: Page 72 in the Fibel By aiming the gun at the target bottom and setting the weapon elevation for 1000m, the Fibel predicts that the trajectory will fall onto a 2m high target at all ranges out to 1000m. In practice, the method would appear to result in less than 100% hit probability due to random scatter and a maximum trajectory height which is over 2m (the following calculations assume infinite target width and represent vertical hit %): 88L56 APCBC Mean Trajectory Height Above Target Bottom 2m High Target 1000m Aim Range ================================= 0.77m at 100m (all hit) 1.41m at 200m (all hit) 1.86m at 300m (73% hit) 2.14m at 400m (31% hit) 2.25m at 500m (22% hit) 2.17m at 600m (32% hit) 1.94m at 700m (56% hit) 1.47m at 800m (88% hit) 0.83m at 900m (94% hit) 0.00m at 1000m (half miss low) The German ballistic table for 88L56 APCBC indicates a maximum trajectory height of 2.3m with 1000m aim, which is consistent with the above results. In view of the relatively low hit percentages from 400m to 600m, the highest first shot hit probabilities at those ranges would probably be obtained with the triangle based range finder or visual range estimation. Improvements to the above noted first shot accuracies might be obtained by correcting the range for misses (add 150m if low, deduct 150m if high). The optimum hit percentages would be obtained by setting the gun for an 850m range and aiming at target bottom, as the following hit probabilities show (the 1.62m maximum trajectory height allows for hits on a 2m high target when the scatter is up): 88L56 APCBC Mean Trajectory Height Above Target Bottom 2m High Target 850m Aim Range ================================= 0.65m at 100m (99% hit probability) 1.14m at 200m (99%) 1.46m at 300m (99%) 1.61m at 400m (92%) 1.59m at 500m (90%) 1.38m at 600m (96%) 0.97m at 700m (99%) 0.38m at 800m (80%) 0.00m at 850m (50%) 5. CONCLUSIONS The procedures and gun sight layout which are discussed in the Tiger Fibel present a system that appears to be superior to the Sherman tank (75mm gun), and the Fibel does not include other advantages such as the superior light gathering characteristics of German optical glass. In one recorded case, a Tiger was able to target and hit massing T34’s through a fog due to the excellent sights while the Russian tank crews were unable to locate the source of the fire. The Americans also noted in a report to General Eisenhower that their tank optics were inferior to the Germans during reduced light conditions. 6. INTERESTING ASIDE ON TIGER TURNING RADIUS While not related to weapon accuracy, one of the Fibel pages shows a series of turning radius for the Tiger, and the tank was able to change its facing by 90 degrees within a lateral distance of 4m (4m turn radius). American sources note that the Sherman required a good sized field to accomplish a 90 degree turn compared to the distance used by a Tiger.