rexford

Daniel previously mentioned that a target at 500m with 2.5x gun sight magnification would appear as if it were at 250m. The actual range would be 200m (500m/2.5). A 3m x 3m vehicle at 500m using 2.5x magnification would appear to be: 3m x 12"/200m, or 0.18" (0.46cm) on each side. Using scissors scopes, the same target would appear to be: 3m x 12"/(500m/14), or 1" (2.54cm) on each side. To see what the above dimensions mean, hold an object the same size as the above calculations 12" (30.5cm) in front of your face. The above calculations are based on the relative size at 12" from the eyeball. As an aside from the above calcs; given the relatively small percentage of the general population that is able to make full use of the stereoscopic rangefinder, what are the chances that every StuG III, Nashorn or Panther crew had such a visually capable crewmember able to use the sight in a fluid, combat situation?

I'am not so sure that the scissors was used to "measure" range, since the scissors were used to observe fall of shot after "letting the cross-level settle down" (which means what?). Anyway, if scissors scopes are not used in the fully extended arms manner, which it appears they usually weren't, they would not appear to "measure" range as much as "estimate" range since the accuracy would be less than optimal. Any idea what the decrease in accuracy would be when scissors scopes are used in the normal, relatively "arms close together" manner that the pictures suggest?

And that pic shows a much shorter baseline between arms than 90cm, so the relative accuracy would be less than ideal (or as originally quoted on this thread).

And in most of the pictures the scissors scope arms seem to be very close together. Best accuracy at 90cm, how close in those pictures where the scissors are protruding above the turret or SPG top? Various sites on the German stereoscopic rangefinder indicate that a small percent of people have the needed vision, and even among those that do their power to use the scope varies widely from day to day. Between all the variables it would seem that the high accuracy quoted in the earlier posts could be a sometimes thing as opposed to the norm.

When a track link is added to highly sloped armor, the links may result in decreased ricochet forces and therefore aid in penetrating the armor. This is what the German tests suggest. Maybe the links act like shot traps. It would seem that there is not enough time or distance to really rotate the round through the track link, so helping to keep the round more horizontal may be a possible explanation for the German tests with track pieces at various angles.

There appears to be something wrong with the above analysis, and the Tiger Fibel presents a slightly different instruction which is echoed in the Panther Fibel. If a 3m high T34 is spotted at 1000m, it would appear to be 3 mils high. The German Fibel instruction for range setting is to take the perceived height, divide it by 2, multiply by 100m and add to the range estimate. So a 3m high target at 1000m would result in a 1150m final adjusted range estimate. And a 3m high target at 1050m would result in a 1200m range estimate. Check the example of crew range estimate averaging in the Tiger Fibel, page 66 or 67 I believe. The Germans show many drawings in the Fibel where the purpose of one half the perceived height times 100m is meant to hit Elvira in the navel even though the gun sight is lined up with the target bottom. For a 2m high target at 500m, the perceived height on the gun sight is 4m and 100m times half the perceived height adds 200m, for a 700m gun setting. There is a drawing in the Tiger Fibel which directly illustrates this example, 2m high Elvira at 500m and a 700m aim to put a shot through her navel. If a target is at 1000m and one aims the 88mm L56 APCBC at 1300m range and target bottom,the average trajectory will be about 2.95m above the aim point or target bottom. This will miss a T34 quite often, and will miss many other targets if some of the tank bottom is shielded by small folds or curves in the ground. If the target is at 1000m and one aims at target bottom and 1150m, as noted above, the average trajectory will be 1.46m above target bottom. 1.46m above target bottom is close to half way up on a 3m high target. Please also note that a 3m high target which appears to be 3 mils high at 1000m will look like 3.75 mils at 800m, not 4.5 mils. And that 3m high target will appear to be 2.5 mils high when it is at 1200m, not 2.25m. The perceived height at any range equals perceived height at 1000m (3 mils) times 1000m divided by actual range. [ August 04, 2004, 02:54 PM: Message edited by: rexford ]

Tom Rodwell indicated that the StuG IIIA scissor scope had 5X magnification, and could be used for range estimation. Wittmann primarily used the scissor scope to hide in ambush and look over the vegetation hiding his StuG. One web site had a modern stereoscopic range finder with 14x magnification, 3 degree FOV and 90cm width, which seems consistent with an earlier post. From what was said on this thread, scissor scopes are not range finders unless both arms are horizontal, which seems to be what several web sites I looked also suggested. In the pictures of tank, StuG and JgPz use the scissor scopes are not horizontal, which suggests that they would not and could not be used for range estimation. So with little door openings with scissor scopes protruding above the vehicle top, scissors scopes would have a limited use and benefit. A book on Tiger tanks indicated some Tiger E's had a stereoscopic range finder holder built on top of the turret. There are many pictures of 88mm Flak crewmembers holding and looking through a stereoscopic range finder which appears to be about 90cm wide. The range finder has both arms horizontal in all the pictures I've seen.

Daniel, Where did you get the idea about setting the gun range setting default to 1000m and aiming below the tank to bring the trajectory onto the target? Is this tactic limited to German tanks in WW II-Online? We have been discussing whether the Germans used a "battlesight" type aim during the war, where the gun range would be set to 800m and shots would be aimed at target bottom, resulting in a trajectory below or close to the target height at all ranges. The Tiger 88L56 firing APCBC would score over 92% average accuracy against a 2m high target from 0m to 700m if the range were set at 800m with target bottom aim. The Panzertaktik book states that German tanks would carry an AP round in the gun and the range set to 800m or 1000m. Our calculations indicate that those range settings together with target bottom aim would result in a high average hit probability at the following ranges: For APC or APCBC ammo: Over 90% from 0m to 700m, over 70% from 700m to 800m: 50L60, 75L48, 75L46 and 88L56 Over 90% from 0m to 800m, over 70% from 800m to 1000m: 88L71 and 75L70 Lorrin

To be strictly picky and pickily strict, the book does not actually say that the first shot would be fired at the pre-set range. By way of analogy, the SLR I carried in my TA days had sights adjustable to 200, 300, 400, 500 or 600 metres. The sights were, as a matter of routine, set to 300 metres. That did not mean that you were not expected to make a correct sight-setting if firing at a different range. I wonder if similar thinking was behind the British early-war practice of aiming at the bottom of a tank target. The Royal Armoured Corps abandoned this practice and adopted the current on of aiming at the centre of mass, and I believe their gunnery standards improved as a result. All the best, John. </font>

Analysis of that 100mm round casting between T34 nose and glacis showed it to be junk, full of bubbles and very poor resistance. We speculate that the 75mm thick T34 driver hatch was high hardened to 440 Brinell like the rolled armor, and we think that 440 Brinell would resist the same whether rolled or cast.

AFV Interiors indicates that the scissors periscope was occasionally found in tanks.

"It is also stated that the gunner is trained to open fire on his own initiative, with the possibility of being overruled by the TC. Mention is also made of using AP as the usual "battle-carry" round, and a range of 800 or 1000 metres already set on the sights." That's it! Set the range for 800m or 1000m before the target comes into view, and then adjust fire onto the target and use that one range for all shots from point blank to 800m. That is what I was looking for. Our calculations showed that using a range setting of about 800m with aim at target bottom would result in a high percentage of first round hits from point blank to 800m against 2m high or taller targets. 800m would work great for 50L60, 75L48 and 88L56, and 1000m for 88L71. 1000m range setting would probably catch most 2m high targets from 800m to 1000m.

Thanks John. Interesting that there is no mention of range estimate averaging by the tank commander (gunner estimate weighted twice as much), as included in Tiger Fibel. [ August 02, 2004, 01:51 PM: Message edited by: rexford ]

My claim about Panther accuracy is not incorrect, just applies to the first shot when the range is not precisely known. I think you may be a little quick to disregard opinions sometimes. ;o) The Tiger Fibel has considerable write-up on the range estimation averaging method, and even if the driver were excluded by the situation the commander and gunner together would produce a better estimate than one guy alone. I don't see how a scissors scope is going to allow range finding like with a stereoscopic range finder. Could you provide some details to help me understand what would happen? Tom Rodwell did an analysis of Michael Wittmann's heroics with a StuG IIIA or B against T34's, where he used the scissors scope to ambush the enemy and produce better range estimates. Tom's reasoning on the scissors scope impact on range estimation was that the stereoscopic view (two eyes) allowed the user to better estimate range than with the normal gunner's sight (one eyeball). Interesting issue. Lorrin Thanks. Lorrin

"The T-34 also had the drivers hatch in the sloped front, reachable by shots (as opposed to other tanks who have the hatch at the top). You can upgrade the nose armor all you want, the hatch will always be a weak point. so it makes more sense to invest the weight elsewhere." The driver hatch on the T34 was 75mm thick, which made it inpenetratable to Tiger hits at any range unless they landed near or on the edges. German penetration drawings for Tiger 88mm ammo against the T34 front show that hits on the driver hatch were not expected to defeat the armor. Sounds like the Russians wanted to spare as many drivers as possible, and the bow machine gunner and turret crew were secondary in terms of armor protection to the driver. My guess as to why the T34 front armor was not seriously ungraded: the tank was intended to quickly blow through infantry lines and do all sorts of damage and adding armor to protect against PzKpfw IV's and Tigers would get in the way of the main T34 mission. We read some time back that Stalin was talking about quantity versus quality, and he stated that the life span of a tank was short and quality didn't matter much in the long run. German tactics also stressed knocking out T34 from the side to reduce the number of return shots, and 76.2mm HE was very lethal against anti-tank guns. Putting all that plate on the front hull would save some T34 but endanger the rest by slowing them down and allowing more flank hots by the panzertruppen.

There is firing test proof that thin armor plates can radically change the direction of big rounds. U.S. tests with thin plates showed that 90mm solid shot rounds were deflected enough to damage the ammo and greatly decrease their ability to penetrate spaced plates behind the thin armor. The Panther Fibel photo's show that a horizontal round penetrating a sloped plate pierces the armor heading downward, which shows that hitting things at an angle can result in a major change to the projectile flight path. If the Panther Fibel photo's showed a second plate sloped at the same angle as the front plate, the penetration of the first plate would actually result in the round being rotated closer to the perpendicular of the second plate. While I don't know that much about the Russian Battlefield discussion, spaced armor can deflect and rotate penetrating rounds enough to do all sorts of things.

A very good point. We were sent some data a long time ago about German firing tests against armor with added track links for protection. While I don't remember the specifics very well the track links added to the resistance at one set of angles, did nothing at the intermediate set of angles and actually degraded the armor resistance at the remaining angles. From what the above post indicates it is a good bet that the track links decreased the resistance at high angles by rotating the round so it was closer to the armor perpendicular. Addding stuff on top of armor is not always a good idea, as Mike points out. We have never found any firing tests that apply to high hardness armor placed on top of other high hardness armor, which is what would occur with T34's. Firing tests against medium hardness homogeneous armor show that 15mm welded to 45mm would resist like less than a 60mm thick single plate (although two face-hardened plates in contact with resist like more than the combined thickness).

I was told that the Panzertaktik book has a discussion on page 487 of a German technique that allows quicker fire with a high hit %. The technique would be similar to U.S. Battlesight aim, where guns would be aimed at a range where the trajectory height never exceeds the target tank height. Is the books' discussion worth buying the book? We have German ballistic tables where the 50L60 APC, and APCBC for 75L48 and 88L56 guns, would not exceed a 2m flight path height if they were aimed for 900m shots at the target bottom. This suggests that a "Battlesight" aim technique may have been used by the Germans, resulting in higher rate of fire and increased hit probabilities. We were also told that one of Patrick Agte's books has something on a similar panzer crew tactic for aiming at a range where the trajectory height does not exceed the target height, but the specific book was not identified. May have been something about German Tiger Commanders. Anyone familiar with the Agte series of books? Thanks for helping out on this stuff. Lorrin

Here are the DeMarre estimates for 90mm HVAP from 76mm HVAP at ranges out to 2000 yards: 0 yards, 3350 fps, Actual is 315mm, DeMarre is 317mm 500 yards, 3125 fps, actual is 284mm and DeMarre is 287mm 1000 yards, 2915 fps, actual is 257mm and DeMarre is 260mm 1500 yards, 2700 fps, actual is 229mm and DeMarre is 233mm 2000 yards, 2500 fps, actual is 203mm and DeMarre is 209mm Not as close as with Russian 85mm HVAP but less than 2% error to 1500 yards. Interesting to note that Russian 85mm HVAP tungsten core is 27.8mm diameter and 0.65 kg weight while U.S. 90mm HVAP core is 47.8mm diameter and 3.62 kg. U.S. rather generous in use of tungsten. Russian 76.2mm HVAP combined a tungsten core and a steel follow-up plug to increase total weight of penetrator while conserving tungsten. Lorrin

Good point. At 400 yards the HVAP round with 17 pdr APCBC propellant would probably do the range in 0.4 seconds or so, with a gravity drop of about 0.8 meters. I guess they didn't really look at the situation like you did, cause it sure does seem like an exact range setting would not be needed to hit the glacis plate. Sounds like they were bureaucrats and didn't like any loose ends no matter how insignificant. On the other hand, a definite sight setting would allow aiming at the nose armor and the spread of shots would indicate relative accuracy. A round that drops 0.8m or so in 400 yards could miss the nose armor unless the range setting was close to the target area center. You're the first one to ever ask why a range setting would be needed at the ranges which were involved with the hybrid ammo types (HVAP with 17 pdr propellant).

The German definition of a complete penetration that I used in my posts came from the British BIOS report, where they interviewed captured German arms and armament workers, researchers and theorists during and after the war. Very interesting that a partial penetration could result in significant crew injuries within a tank. Did not know that. One other interesting point is that British firing tests with German 75mm and 88mm APCBC showed that the HE burster was not working on 45° and 55° angled hits (measured from perpendicular or vertical). Penetration of highly sloped plate results in a large cross stress on the projectile body, since they are first rotated upwards as in a ricochet and then they turn downwards and penetrate in a downward motion nose first as the plate gives way. Page 15 in the Panther Fibel presents some photo's of rounds penetrating plate at various angles, and the 45° pictures show how the round is first moved upward and then passes through the plate moving downwards. The penetration at 30° from vertical also changes direction from upwards upon initial impact to horizontal after penetration.

Phil Gollin posted the following data on the AFV News site: "Weight of core 8 lbs, diameter 1.88 inches, total projectile weight 16.8 lbs. According to the report : "Contray to British practice, the tungsten core of the American 90mm composite rigid shot has no steel sheath nor other protective devices to give good spaced plate performance."" If the U.S. 76mm HVAP round penetrates 247mm at 0 degrees and 3400 fps with a 3.9 pound tungsten core (1.5 inch core diameter), the DeMarre equation predicts that 90mm HVAP would penetrate 317mm at 0 degrees and 3350 fps. The actual is around 313mm.

CMAK is more accurate in quite a few ways, after going through the stats and the results. CMBO penetration for 75mm APCBC fired by Sherman is higher than it should be against homogeneous armor (Tiger, for instance), and lower than it should be against face-hardened armor (PzKpfw IVH and StuG IIIG fronts, for instance). CMAK takes into account the different penetration stats for rounds against face-hardened and homogeneous armor, which makes a BIG difference in many cases. Sherman 75mm APCBC penetrates about 81mm homogeneous armor at 500 meters and 0 degrees, but about 95mm of face-hardened armor at the same range and angle. The armor piercing cap on Sherman 75mm APCBC was designed especially for face-hardened armor destruction (the cap protects the projectile nose), but the armor piercing cap also decreases homogeneous penetration by absorbing more energy in the cap break-up than it contributes to armor defeat. CMBO also takes into account projectile size and HE burster after it gets into a tank, so 37mm APCBC which is solid shot does less damage after penetrating a Panther than 75mm APCBC which has a nice fat HE burster designed to explode after penetration. There are pictures of Valentine tanks that took MANY 50mm hits and penetrations and kept on fighting. How many 122mm hits could the same tank take? Lorrin

There does seem to be a question mark over correct sighting being used: "Insufficient firing was conducted with 76mm HVAP projectile with 17pdr APCBC and 17pdr SABOT propellant to determine definite sight settings for a conclusive accuracy test." </font>

Maybe I wasn't too clear because I meant something else. The following will hopefully clear up what I meant. The German criteria during their penetration tests was that the round had to penetrate the plate with the HE burster intact and capable of detonating. If the round penetrated and the HE burster was damaged the round was not credited with a penetration.