rexford
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Accuracy Data for 88mm Flak
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
Michael, Do you have the ballistic table for 88L56 Pzgr 39 fired at 800 m/s? Would it be possible for you to post the flight time and velocity figures from 0 to 2000m in 200m intervals? Or to email me a copy of the scanned page? Thanks. Lorrin 
Accuracy Data for 88mm Flak
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
100% dispersion data is not real in the sense that weird wild rounds can always be just a little further out if one goes from 1 million to 10 billion rounds. The 90% zone for 17 pdr APCBC at 1000m is 1.19m high and 1.01m wide. The corresponding 68.26% zone dimensions are 0.73m vertical and 0.61m lateral. The 50% zones for 17 pdr APCBC at 1000m would be 0.49m high and 0.41m sideways. The 50% zones for 88L56 APCBC at 1000m are 0.4m and 0.2m. Keep in mind that the German figures are averages, so many guns would be vastly superior and many would be really awful looking. 
Theoretical Hit Rates Against Hulldown Targets
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
A hulldown Panther would, in reality, have only the turret front/mantlet exposed, sometimes stuff below the gun would be hidden. For a hulldown Panther to only be hidden at lower front hull level, with the giant glacis fully seen, doesn't seem realistic. 
When one aims at the front of a Panther the hits concentrate around the center of mass, on the glacis, and hit the mantlet when they scatter about. When on aims at a hulldown Panther the mantlet center is the center of mass. But the Panther mantlet is about 2' tall compared to about 8' for the Panther, so the chances of hitting the mantlet are about onefourth of those for a hit against the entire frontal aspect (turret and hull). Computer runs for a Tiger firing on a hulldown T34 or M4A3(W)75 Sherman predict that the hulldown hit percentage will be about onethird of the hull exposed rate. Would be interesting to see if turret front hit % goes up with hulldown target even if overall hit percentage goes down. Will do it soon. Interesting points on this thread.

If one places a shot so it hits off the side of the front of the curved mantlet on a Hetzer, StuG IIIG or JagdPanther, the round may get squeezed into a channel where it comes into contact with a flat plate area. A shot trap, as was mentioned in another post on this thread. Regarding the Panther mantlet, it was not uniformly 100mm in thickness but thinned out towards the upper and lower edges, reducing to about 75mm at the edges. The IS2 mantlet also thins out towards the upper and lower edges. My analysis used 100mm at all angles, which overstated the armor resistance at some angles but works okay at the larger angles where nothing is going to penetrate anyway. When I have the time I'll adjust the armor figures for actual thickness changes with angle.

Accuracy Data for 88mm Flak
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
Great info Michael! Thanks so much. Lorrin 
Accuracy Data for 88mm Flak
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
Michael, A few questions on the terrific data you posted: The last two dispersion results have the lateral first and then the vertical: 8.8 cm Pzgr. fired from 8.8 cm Flak: 100  ? x ? 500  0,3 x 0,2 (should this be 0,2 x 0,3?) 1000  0,7 x 0,4 (lat and vert seem reversed) 1500  1,1 x 0,6 (ditto) 2000  1,6 x 0,8 (ditto) The vertical and lateral dispersion appear to be reversed for the above ammo and gun, should it be: 1000  0,4 x 0,7 1500  0,6 x 1,1 2000  0,8 x 1,6 8.8 cm Pzgr. 39 fired from 8.8 cm Flak: 100  0,1 x 0,1 500  0,3 x 0,2 (lat and vert reversed?) 1000  0,5 x 0,7 1500  0,8 x 1,1 2000  1,0 x 1,6 8.8 cm Pzgr. 39 fired from 8.8 cm Kw.K. 36: 100  0,1 x 0,1 500  0,2 x 0,2 1000  0,2 x 0,4 1500  0,3 x 0,6 2000  0,5 x 0,9 The dispersion figures for 88mm Kwk 36 firing Pzgr 39 are the same as the table listings for Pzgr 391 and 39 A1. Dou you know what major differences existed between Pzgr 39 and 391 and 39 A1? I see a FES tag on the 391 and 39 A1 ballistic table. Interesting that the 88mm Flak firing Pzgr has the same vertical dispersion as the 88mm Flak firing Pzgr 39 but less lateral dispersion. So the earlier 88mm Pzgr was more accurate than the later Pzgr 39 when fired from the 88mm Flak with a constant aim. Thanks. Lorrin 
Accuracy Data for 88mm Flak
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
Good info and glad you joined the discussion. Do you know the breakdown of 88mm Pzgr 39 rounds used by the Tiger in terms of Pzgr 39 vs Pzgr 391 and Pzgr 39 A1, and when the various rounds would have been used. The ballistic table I have is for the 88mm PZgr 391 and 39 A1, with a 10 kg round fired at 780 m/s. It is good news to hear that the 800 m/s muzzle velocity and 10.2 kg weight are appropriate for 88mm Pzgr 39 but how common was Pzgr 39 relative to the other two projectiles (391 and 39 A1). With an 800 m/s muzzle velocity and a 10.2 kg round, the Tiger trajectory to 1000m would attain a maximum height of about 2.14m as opposed to 2.25m for a 780 m/s muzzle velocity. A little better. Do you know if the German Tiger crews actively used a sort of battlesight aim (aim gun at target bottom, set gun for 800m to 1000m range and then hit all 2m tall targets between gun and range setting? Did they actively use the gun sight triangles for range estimation? I figured all along that the 88mm L56 Flak would not have the same dispersion as the Tiger tank gun based on the stability of the mount. Thanks for the great info, it's appreciated. Lorrin 
What Tiger Vets Say About Range Estimation
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
Battlesight aim works by aiming at the target bottom and then elevating for an 800m to 1000m shot, which is how my calculations went earlier in this thread. If one elevated the gun for an 800m to 1000m shot and then pointed at the target bottom they would probably end up with the same situation as doing it in the reverse fashion. One is basically adding the angle from gun to target bottom to the elevation needed for an 800m to 1000m shot, and it would seem that the order would not be important. 
The cast mantlet on the Hetzer, JagdPanther and StuG IIIG appears to present an inpenetratable angle to incoming rounds over most of the area that would be hit on a frontal shot with no side angle.

There are two types of curved armor on tanks, in general. Many mantlets assume a circular shape, going from a 0 degree from vertical angle at the center to close to 80 degrees from vertical at the upper and lower edges. And there are the rounded mantlets (Saukopf) where the angle goes from 0 degrees from vertical to a high value very quickly. For the Panther mantlet, assume a half circle, and the following impact angle distribution applies for even spread of shots across the height (vertical resistance to 17 pdr APCBC hits is in brackets and is taken at angle half way thru angle range, and cast armor resists with quality factor of 0.95 so 100m cast = 95mm rolled): 9% strike at 5 degrees or less (95mm vertical) 8% at 5 to 10 degrees (96mm) 9% at 10 to 15 degrees (98mm) 8% at 15 to 20 degrees (101mm) 8% at 20 to 25 degrees (106mm) 8% at 25 to 30 degrees (113mm) 7% at 30 to 35 (124mm) 7% at 35 to 40 (138mm) 7% at 40 to 45 (158mm) 6% at 45 to 50 (186mm) 5% at 50 to 55 (226mm) 5% at 55 to 60 (282mm) 4% at 60 to 65 (359mm) 3% at 65 to 70 (467mm) 3% at 70 to 75 (602mm) 1% at 75 to 80 (824mm) 2% at 80 to 85 (1324mm) 0% at 85 to 90 If 17 pdr APCBC hits are evenly spaced across the vertical height of the Panther mantlet, there is no side angle from gun to armor facing and the round penetrates 160mm at a given range, 29% of the hits will have less than a 50% chance of penetrating, about 25% will never penetrate and about 57% or so will always completely penetrate. Note that the 30 degree resistance is not a good model for the rounded mantlet resistance, because using 30 degrees results in an estimate of 113mm which is penetrated all the time by 17 pdr APCBC and U.S. 76mm APCBC hits, while using the full angle complement results in less than a 100% success rate. I never said 30 degrees was a good angle to use for rounded armor and have always suggested that a distribution be used.

What Tiger Vets Say About Range Estimation
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
JasonC's point about aim variations is on the mark with regard to battlesight aim, the major problem is trying to guess how large the factor would be. The high accuracies that are predicted with perfect aim at target bottom would be lowered if the aim point were allowed to vary about the bottom of the target, which would be expected in real life. On another subject and this is the last time I will say it, the Germans were aware (published ballistic tables) that if they aimed the 88L56 at the bottom of a 2m tall target and set the range to 900m, they would have a good chance of hitting the target at all ranges from 0m to just under 900m. Battlesight aim in everything but name. 
What Tiger Vets Say About Range Estimation
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
"Since the German gunners supposedly aimed at the target bottom anyway, it can not be assumed that they were using battlefield sight." The standard gun setting procedure for the Germans was to aim the gun at the target bottom and then add to the initial range estimate to bring the trajectory up to the target midpoint. The adjustment was based on half the perceived target height in mils times 100m. I've said this many, many times. Battlesight aim and standard targeting are NOT the same for the Germans. Not the same. If the range is set at 800m to 1000m for the first shot and the aim is at target bottom, it is battlesight aim. This procedure is noted in the German ballistic tables. CG on the Yahoo! Tankers site brought up an action during which T34's were charging Wittmann's Tiger (T34's were charging Tigers to ram them, and they had damaged one Tiger earlier in the action), and the gunner used a constant range estimate against the Russian tanks to get off as many shots as possible in the time they had. Battlesight aim in the above action would consist of setting the range setting to one figure and then repositioning the triangle do it was at the bottom of the next T34 to be fired upon. I do not care to speculate as to whether the triangles were moved up or down to adjust ranges since there does not appear to be any reason to suspect that it was done other than some gamers in Panzer Elite. Do you have something solid upon which you speculation is based? [ September 08, 2004, 01:09 PM: Message edited by: rexford ] 
What Tiger Vets Say About Range Estimation
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
It is worth noting that neither the Tiger or Panther Fibels provides any direct advice regarding the use of battlesight aim. However, the effective range for use of the battlesight aim technique against a 2m high target is indicated in the German ballistic tables for every armor piercing and HEAT round: 50L60 APC, 75L48 APCBC and 88L56 APCBC: 2m trajectory height or less at 0900m range interval will result in a high hit probability against 2m tall targets with 900m aim 88L71 APCBC: 2m trajectory height or less at 01200m range interval will result in a high hit probability against 2m tall targets with 1200m aim It cannot be stated at this point with certainty that battlesight aim was very prevalent and was used as a common tactic among panzer troops and antitank gun crews, although the research has just started and will be continued. It is likely that the best gunners may have used the technique with good results, and the Panzertactik book indicates that crews routinely loaded armor piercing rounds and set the gun for 800m to 1000m ranges prior to initial contact with the enemy, which suggests battlesight aim was used widely. 
What Tiger Vets Say About Range Estimation
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
What's the point? The issue here is a firing technique where the gun is initially aimed at target bottom, and then is elevated a given amount for a 1000m shot (8.9 mils or 0.5 degrees). I already showed that regardless of gun elevation, if one aims at the target bottom at a given range and elevates thegun above the initial angle for a 1000m shot, the height above target bottom will be the same. If you would examine my physics calculations and show me a mistake or incorrect assumption I will be glad to revisit this topic in the future. [ September 07, 2004, 06:45 PM: Message edited by: rexford ] 
First Round Accuracy of German Tungsten Core Ammo
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
“In Tiger TanksGreen on pg 46, there is a report from British testing of a Tiger I gun. Its stated that a 5 shot group of 16in by 18in was obtained. Note that it is not saying that is the 50% zone, its saying that all 5 rounds landed in that area at 1200 yards (1100m).” Range is close to 1100m. All 5 test rounds land within a rectangle of 0.41m lateral by 0.46m vertical. German dispersion data has a 50% zone at 1100m of 0.44m vertical by 0.26m lateral. So it would seem, at first glance, that the Tiger test mentioned above was an aboveaverage weapon or the ammunition it fired was better than average, interms of vertical dispersion. The lateral dispersion isn't out of line with a 50% zone of 0.26m at 1100m. 5 rounds does not prove anything because even a poor gun with large dispersion could conceivably place 5 rounds in the small area. It also has to be remembered, as shown in the test with five Churchills, that wide variations could occur from one tank to another and that the average dispersion would not apply to most tanks. “Krupp’s Main Range, Meppen For guns required to be very accurate (eg. tank and antitank guns), about 95 per cent of rounds fell within a rectangle 60 cm. high and 30 cm. wide on a vertical target at 1,000 metres. It was stated that the dispersion for line is less than for height. The ratio of lateral to vertical dispersion remains substantially constant at all "flattrajectory" ranges for any gun. The angular dispersion also remains nearly constant with range in the flattrajectory region.” 95% of rounds expected to land within a 0.60m vertical x 0.30m lateral box at 1000m. Tiger dispersion data at 1000m has 50% zone of 0.40m vertical and 0.23m lateral, which relates to a 68.26% zone of 0.60m vertical and 0.345m lateral. 95% zone based on Tiger dispersion data for 50% zone works out to 0.60m x 1.96 or 1.18m vertical, and 0.345m x 1.96 or 0.68m lateral. Looking at the 95% zone from the German 50% zone data and the statement in quotations, it seems that the author of the above statement forgot to double the 0.60m x 0.30m figure, which probably represented the bottom or top half of the target rectangle instead of the entire upper and lower halves. I would also guess that his statement was an approximation. 0.6m x 0.3m. It is obvious that the 75L48 APCBC could not come close to the 0.6m x 0.3m 95% zone. British 17 pdr APCBC has a 90% zone of 4.1 minutes vertical and 3.46 minutes lateral, which is much greater than 0.6m x 0.3m at 1000m. I question the above statement and feel it is the half size box. 
First Round Accuracy of German Tungsten Core Ammo
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
British 90% zone for 17 pdr APCBC is 4.1 minutes vertical and 3.46 minutes lateral at 1000m. Compare that to 88L56 APCBC 50% zone at 1000m and see which is better. 
First Round Accuracy of German Tungsten Core Ammo
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
They were not testing for dispersion, they were checking the mean point of impact and a short range was effective because dispersion would be so small as to be a nonfactor. 
What Tiger Vets Say About Range Estimation
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
"Are you using the same superelevation (that is, firing at 1000m) as a 2m tall gun as a 0.5m tall gun." Yes, it should be clear from the math in my previous examples. "It would seem that there would be a shift downward all along the trajectory line which would move the '1000m' shot much shorter. Ie, it would need more superelevation then." No. Analysis of many trajectory runs on the computer shows that the changes are insignificant (very small)and can be disregarded. "For the case where the gun is actually at zero height, there is no correction from deptressing the barrel at targets that are closer. This effect essentially disappears." Don't understand your point. When the gun is at 0m (same elevation as target bottom) it is initially aimed at the target bottom at the start, and would be elevated 8.9 mils for a 1000m shot. What effect disappears? "Like the StuG example above, the non dispersion gravity driven ballistic flight will exceed 2m." I already stated in the initial posts that the trajectory for 75L48 and 88L56 shots will exceed a 2m height for 1000m aimed shots and would miss a 2m high target at quite a few ranges between 0m and 1000m. The previous examples show that battlesight aim does not depend upon the relative height of the gun barrel with respect to the target bottom. The gun is aimed at the target bottom, it is then elevated for a 1000m shot and the rest is physics. Do you understand how the German gun sight worked? Please look at the Tiger Fibel drawing, first one places the aiming triangle just under the target bottom and then one adjusts the aim range setting which is on the outside of the sight. 
Theoretical Hit Rates Against Hulldown Targets
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
The calculations were based on the Tiger aiming at the center of the observed target area. Using the standard German practice, the aim would initially be aimed at the bottom of the observed target and then half the perceived height in mils times 100m would be added to the range estimate. A 0.7m turret at 800m looks like 1 mil, so add 50m to the 800m range and obtain 850m for the mean point of impact. Aiming at 850m with an 800m target results in a shot 0.37m from the bottom, which is close to the midpoint at 0.35m. The aim at bottom without range adjustment worked for fully or mostly exposed targets, and would not work very well for hulldown targets. 
What Tiger Vets Say About Range Estimation
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
No, the height of the Tiger gun above the ground is not a factor as long as it doesn't become radical (like on top of a 20 story building). For a 200m battlesight aim shot at a T34 where the Tiger gun is 0.5m above the T34 bottom: The angle from Tiger gun to T34 bottom becomes minus 0.143 degrees, the gun is elevated plus 8.9 mils (+0.50 degrees) above the initial aim for 1000m and the overall angle after elevation is +0.357 degrees. The elevation of the round at 200m equals: 200m x tangent(0.357 degrees)  0.5 x 9.81 x 0.26squared, or 0.91m above the gun, which when added to the gun elevation (0.5m) becomes 1.41m above the T34 hull bottom. Same result whether the Tiger gun is 2m above the ground, or 0.5m above the ground. If the Tiger gun is 2m below the T34 bottom, the gun is initially aimed at plus 0.573 degrees, and is then elevated 0.50 degrees for a 1000m shot, so the final angle is 1.073 degrees. Shot elevation at 200m distant T34 equals: 2m + 200m x tangent(1.073 degrees)  0.5 x 9.81 x 0.26squared = 1.41m above the T34 bottom. Same ole 1.41m above the T34 bottom. Like I said some time ago, the actual height of the Tiger gun is not an issue relative to the T34 bottom aim in most cases. 
Theoretical Hit Rates Against Hulldown Targets
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
Hulldown suggests nothing but the turret is visible, which was measured at about 0.70m from some scale models. It worked out to about onethird the total height for T34 and Shermans. Against a "hulldown" Marder, where 0.82m of the vehicle is visible over the ground, a T34 firing APBC would have a 14% first round success rate at 800m once the Marder was clearly seen. But at 800m, 0.82m of the Marder would appear to be 0.75mm tall, or 0.03", even after T34 gun sight magnification is considered. Hold out a ruler at one foot from the face and look at a 1mm line, and then picture a 0.75mm tall Marder figure poking out from behind a small hill. A 0.75mm high figure (measured at 12" from the eye) is small, and the T34's might have trouble locating the tank apart from the dust and smoke associated with the shooting, especially if there is elevated ground behind the Marder so it is not standing out against the top of a hill. 
Quite a bit of past discussion has centered around the chances of hitting hulldown targets, and I've seen hull hidden Marders die quickly at the hands of far off T34's. So, we did some calculations for first round hit rates against hulldown Shermans and T34's (assume 20% average range estimate error for first shot): T34 Tiger 88L56 vs fully exposed T34 at 800m, 49% Tiger 88L56 vs Hulldown T34 at 800m, 18% M4A3(W)75 Sherman Tiger 88L56 vs fully exposed M4A3 at 800m, 54% Tiger 88L56 vs Hulldown M4A3 at 800m, 18% The hit percentages against a hulldown target vary from 33% to 37% of the hull exposed target case. The above analysis did not consider hits upon highly sloped turret surfaces where a hit would probably bounce off without significant impact or damage. The above estimates are ideal hit scores for a crew that does everything right, uses single dispersion and does not include "sloppiness" modifiers (or double vision effects).

What Tiger Vets Say About Range Estimation
rexford replied to rexford's topic in Combat Mission: Barbarossa to Berlin
See pages 25 and 26 in the Panther Fibel, the trajectory height is measured with regard to the line between the gun and the target bottom. We'll assume the Tiger gun is 2m above the bottom of the 2m high T34, ground is everywhere level, and the gun barrel is initially aimed straight at the T34 bottom. The initial angle from 88mm to target bottom, for a 200m target range, is arc tangent (2m/200m) or 0.573 degrees. For a 1000m shot the gun would be superelevated above the initial aim by 9.4 mils or +0.529 degrees, according to the German ballistic data sheet. So the final aim angle is close to zero degrees, being 0.044 degrees. A slightly downward tilt to the gun. A 200m target takes 0.26 seconds. So, a quick and dirty trajectory estimate for this case is: 200m x tangent (.044 degrees)  0.5 x 9.81 x 0.26 squared or 0.485m. So the Tiger 88 shot at 200m with aim at T34 bottom is about .485m below the Tiger gun or 1.5m above the T34 bottom. My calculations used in the hit percentage estimates assumed that the Tiger shot elevation for a 1000m range setting round aimed at the bottom of a 200m distant T34 target would be 1.41m above the T34 bottom. The difference between the two calculations is due to the use of 9.4 mils for the 88mm aim at 1000m, which is what the Germans list but appears to be high based on my trajectory program computer runs. My ballistic calculations indicated an 8.9 mil superelevation for 1000m shots by the Tiger, which relates to +0.50 degrees. Which raises the initial gun barrel angle to 0.573 + 0.50 or 0.073 degrees for 1000m shots aimed at the T34 bottom. And the simple trajectory equation becomes: 200m x tangent(0.073 degrees)  0.5 x 9.81 x 0.26 squared or 0.59m. Which results in an 88m round trajectory height of 1.41m above the T34 bottom at 200m (0.59m below the Tiger gun which is 2m above the ground). Which is what my battlesight aim hit rate estimates assumed. I trust the above analysis shows that my estimates and statements are on a firm footing and can withstand close scrutiny. 
The Tiger and Panther Fibels show that the range estimate is adjusted by adding 100m times half the perceived height in mils. I think this is the same thing you are saying. If the perceived target height is 3 mils, the range setting is adjusted by adding 3 mils x 1/2 x 100m or 150m to the initial range estimate.