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About rexford

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  1. 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 e-mail me a copy of the scanned page? Thanks. Lorrin
  2. 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.
  3. 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.
  4. 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 one-fourth 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 one-third 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.
  5. 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 IS-2 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.
  6. 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 39-1 and 39 A1. Dou you know what major differences existed between Pzgr 39 and 39-1 and 39 A1? I see a FES tag on the 39-1 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
  7. 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 39-1 and Pzgr 39 A1, and when the various rounds would have been used. The ballistic table I have is for the 88mm PZgr 39-1 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 (39-1 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
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. "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 mid-point. 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 ]
  13. 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 0-900m range interval will result in a high hit probability against 2m tall targets with 900m aim 88L71 APCBC: 2m trajectory height or less at 0-1200m 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 anti-tank 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.
  14. 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 ]
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