rexford
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Posts posted by rexford
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They are both multiplied by the conversion factor.Originally posted by Mr. Tittles:Thats what I thought it was. You seem to have been saying that the zone lengths were both multiplied by the factor. That would spread out the rounds and make zeroing a nightmare.
If the 50% zone is 1m high and 0.5m wide, the 90% zone is 2.44m high and 1.22m wide (1.22m left and right of center and 0.61m left and right of center).
And the doubled dispersion for the 90% zone would be 4.88m high and 2.44m wide.
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Here is a comparison of the 90% zones at 1000m for a few capped AP type rounds:
50L60 APC: 0.81m vertical and 0.73m lateral
88L56 APCBC: 0.98m vert and 0.56m lat
17 pdr APCBC: 1.19m vert and 1.01m lat
75L48 APCBC: 1.37m vert and 1.27m lat
If one doesn't double the dispersion, 90% of the 75L48 APCBC shots at 1000m are no more than 0.685m up or down from the impact center, and no more than 0.635m left or right.
In terms of feet, we're talking a max scatter from impact center (90% of the rounds) of 2.25' vertically and 2.08' laterally.
With regard to the "badness" of the scatter data for 75L48 APCBC, it is similar to the 88mm Flak 18 and 36 firing Pzgr ammo, and is much better than 2 pdr tank killers shooting AP shot.
We've looked at alot of WW II scatter data for 50% and 90% zones, and the 75L48 APCBC figures seem reasonable.
Doubling the dispersion is an attempt to take the basic constant aim scatter pattern, where nerves of steel hold fast to the aim, and mix it up with combat action where nervousness and a possible tendency to shoot before one is hit combines with possible imperfect care of the weapon system to result in not so good an aim as one might do on a proving grounds after a good night's rest and plenty of time to prime up the goods.
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If the 88mm L56 Flak APCBC (9.6 kg) round was designed to be fired at 810 m/s and the 88mm L56 Tiger round (10 kg) was designed to be fired at 780 m/s, there is a chance that they were not meant to be interchanged.
Instead of speculating on whether they were or were not interchangeable we should point out the possibility and leave it at that.
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No dimensional mistake, perhaps you have not seen the actual 50% zones before and they seem out of line for some guns.Originally posted by Mr. Tittles:I am not attacking rexford but I have my doubts about the methodology used here. It may be the Germans methods are screwy.
Basically, the 'scatter' is eliptical in nature. generally, the height difference is greater than the width difference. Since the target size is more forgiving in the width (2.5m vs. 2m), the critical data is the height variation.
If I understand what rexford claims, he is saying that 50% of the rounds could land with a box of 1 sq meter but the other 50% could be in a box of up to 8.5 sq meters or so? This is for single dispersion mind you. The target is only 5 sq. meters.
I suspect some dimensional mistake.
If 50% land within 0.5m left or right of the center, there will be a small probability that one round will land 2.0m right or left. Will almost never occur but could.
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I doubt that the British data is for actual firing tests, they usually calculated data such as Jeff presented. I will find the original report and see if they were calculated, which is what I would guess they are.Originally posted by Mr. Tittles:The above data was cut and paste from an old post by Jeff Duquette.
Note that a Tiger I is not 2mx2,5m. And niether is a Sherman tank (2.9mx2.67m?).
My point is that the German data is for a relatively small target. Antitank fire is sort of a step function in that close don't count when its a miss.
I think the casual reader show note that the German numbers that rexford posted above are calculated numbers based on data about where 50% of the rounds land (we all followed his example about the 50mmL60 APCR at 800m right?). They are using a statistical method to try to fudge in human errors and other factors.
The British data is based on actual firing under pristine conditions. Range is known and everything else is minimized. It is showing the precision of the weapon itself. Notice just how precise it is against a large target such as a TigerI.
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I dropped my internet service and don't have personal e-mail at the library.Originally posted by Andreas:Hi Lorrin
Can you drop me an email please?
Cheers
Andreas
Did you have a question or need a copy of something?
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Plot the data on a piece of graph paper.Originally posted by Mr. Tittles:I really have my doubts about how this data is being analyzed.
If you fire 10 rounds and 5 are nearly kissing each other, but the other 5 are distributed squares away; then you don't have a shot group. You don't have repeatability and you don't have a basis for zeroing. A rule of thumb is that the shot group should be smaller than the target area size!
I would really like to see raw data and am leary of some quantum leaps taking place here.
For a total single dispersion distance of 1.0m (lateral and vertically), the spread of shots is a smooth curve with 50% within 0.5m of the center. And 68% within 0.75m of the center. And 95% within 1.0m.
The shots are bunched up around the center point and the tendency of an individual round to fall further from the center falls off rapidly with distance from the center.
A bell shaped normal distribution curve means it is shaped like a bell, most of the height near the center and very little at the extremes with a rapid fall-off in height from just outside the center to the edges.
Look at a normal distribution curve and you can draw some realistic conclusions from the numbers.
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Tungsten core rounds with a ballistic shape similar to U.S. 76mm HVAP or later war German APCR (75mm and up) would lose velocity much slower than arrowhead and would be more accurate than APCBC shots, with greater accuracy advantages at short and medium ranges.Originally posted by Mr. Tittles:The US 76mm HVAP round was said to be extremely accurate also. I just wonder if they had sights that were marked for this ammo?
Perhaps HVAP/APCR got a bad rap early in the war and it stuck?
The data sheets that went with the ballistic tables indicate that the 50% zones were part of a bell shaped normal distribution curve, and the multipliers which went with it are what would occur with that sort of curve.
During the German firing trials the 1500m results for 75L48 APCBC resulted in 50% of the shots falling within a 0.6m x 0.5m box. So the box was not really a square, the vertical scatter is usually larger than the lateral.
Measured from box center, 50% of the rounds are contained within plus or minus 0.3m from center (about 1 foot), and high or low within 0.25m (10 inches or so).
68.3% of the shots would be within a box about 0.9m x 0.75m (1.5 multiplier after rounding), or 0.45m up or down and 0.38m left or right.
95.5% within a box 1.8m x 1.50m, or 0.9m up/down or 0.75m left/right.
I've looked at ALOT of scatter data for WW II weapons, and the 75L48 APCBC data looks large compared to high quality guns like the 75L70, 88L56 and 88L71 but is similar to the German 76.2L51.5 and other weapons of WW II.
With regard to corrections after a miss, I've stated that the wide double dispersion figures could make good corrections difficult, on occasion, as the range increased.
I don't know if the use of double dispersions would be a good idea for the placement of follow-up shots. Never came to a conclusion on that.
I will get the HEAT and HE data for a variety of guns and ammo and post it here.
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Yes, early 50mm APCR was higher velocity but a much worse ballistic shape so it lost velocity a heck of alot faster.Originally posted by Mr. Tittles:Wasn't the early 50mmL60 APCR higher velocity than the later model (called Pzgr40/1 I believe)?
Should be on Guns and ARmor site.
Also, the 50mmL42 Pnzrg40 was made in some large numbers.
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The “burst on target” method is presented in several different gunnery manuals from WW II as an effective means of correcting for first shot misses. To use the method, the gunner observed the fall of shot in front of the target and immediately elevated and rotated the gun to place the target on the point where the ground hit was observed.
While the method provides a good means of correcting for first shot misses it has limitations:
1. High shots are not as easy to correct for, as one must deduce the height of the round as it passes over the target which would appear to be very difficult.
Graphical review of the ground hit locations from high misses suggests that even if they were observed, such as on wide shots, the perceived ground placement of a high miss would not result in effective aim adjustments.
U.S. Field Manual FM 17-12 does not discuss how one uses Burst on Target with high shots.
2. U.S. Armored Force Field Manual FM 17-12 notes that “Only where impact is on dry, open terrain can the strike of AP projectile on the ground be sensed.” The manual also notes that “Frequently the gunner will be unable to observe consecutive rounds; that is, he will see one round clearly but the next will be obscured by dust or smoke.”
3. U.S. Field Manual FM 17-12 notes that the burst on target method is effective out to 1,000 yards when visibility is good, with bracketing used beyond that range (200 yard changes after the first miss at 1500 yards or less, and 400 yard changes beyond 1500 yards). The German Fibels for Panther and Tiger crews advise them to use “fire for effect” out to 1200m, and bracketing beyond that range (200 range changes after first miss out to 2000m, and 400 changes beyond that distance).
4. Random scatter can disguise and distort the true adjustment, where some misses may have the correct range but the shot fell short due to scatter.
5. Variations could take place in placing the target on the burst point due to human error.
To test the applicability of the Burst on Target method with different guns, a computer simulation was prepared where a firing tank missed on the first shot with a given target range and aim setting, and the second shot was adjusted using Burst on Target. The stationary target was taken as 2m high by 2.5m wide, all terrain was level at the same elevation and the first shot was assumed to follow the theoretical trajectory without scatter, which simplified the mathematics.
The simulation results suggest that Burst on Target works best with higher velocity rounds and at short to medium range, and as the flight time to target increases (lower muzzle velocity) the curvature of the trajectory reduces the second shot hit percentage. Burst on Target is still an effective method to home in on a target for third and follow-up rounds from lower velocity guns but will take time.
The computer results follow, where double dispersion was applied to the follow-up shot trajectory:
SECOND SHOT HIT PROBABILITY USING BURST ON TARGET CORRECTION
1. Target at 1000m, Initial Aim at 700m (30% first shot range estimate error)
75L24 at 385 m/s, 0%
75L40 at 619 m/s, 0%
75L48 at 750 m/s, 19%
88L71 at 1000 m/s, 73%
Note: Muzzle velocities listed after gun, where all projectiles are capped steel AP.
2. Target at 1000m, Initial Aim at 800m (20% first shot range estimate error)
75L24 at 385 m/s, 0%
75L40 at 619 m/s, 11%
75L48 at 750 m/s, 42%
88L71 at 1000 m/s, 81%
3. Target at 1000m, Initial Aim at 900m (10% first shot range estimate error)
75L24 at 385 m/s, 1%
75L40 at 619 m/s, 71%
75L48 at 750 m/s, 73%
Note: Burst on Target correction accuracy significantly increases as initial round gets closer to target for medium velocity projectiles., but does not help low velocity 75L24 shots very much.
4. Target at 700m, Initial Aim at 490m (30% first shot range estimate error)
75L24 at 385 m/s, 0%
75L40 at 619 m/s, 89%
75L48 at 750 m/s, 84%
Note: Reducing the range from 1000m to 700m with a 30% error on the initial range setting significantly improves Burst on Target hit probabilities. for medium velocity guns
5. Target at 700m, Initial Aim at 560m (20% first shot range estimate error)
75L24 at 385 m/s, 0%
75L40 at 619 m/s, 95%
75L48 at 750 m/s, 93%
Note: Reducing the range from 1000m to 700m with a 20% error on the initial range setting significantly improves Burst on Target hit probabilities. for medium velocity guns
6. Target at 700m, Initial Aim at 350m (50% first shot range estimate error)
88L71 at 1000m/s, 93%
Note: Burst on Target is very effective in obtaining second shot hits with the high velocity, flat trajectory 88L71 even with a 50% first shot range error as long as the range is.
7. Target at 500m, Initial Aim at 250m (50% first shot range estimate error)
75L40 at 619 m/s, 67%
Note: Short range shots result in a flatter trajectory, even with the 75L40 gun, so Burst on Target is very effective even with a 50% range error on the first shot.
8. Target at 500m, Initial Aim at 350m (30% first shot range estimate error)
75L40 at 619 m/s, 97%
The second shot accuracy with Burst on Target correction improves with muzzle velocity at a given range, and increases as the accuracy of the initial shot is improved which can occur through decreased initial range estimate errors at a given range or a shorter range with the same percent range estimate error.
The above analysis assumed that the first shot was not impacted by random scatter. During real combat half of the first shot misses would be closer to the target than the simulation assumed (resulting in a higher second hit rate in many cases), and a share of the Burst on Target corrections would be higher or lower than ideal raising or lowering the second round accuracy as the burst placement error required.
It should also be noted that Burst on Target is most or primarily effective for short misses where the ground strike can be observed by the gunner, which would make up less than half the misses as a general rule.
After a 75L24 misses the first two shots at a target with Burst on Target after the first miss, the following hit probabilities would apply to the second attempt using Burst on Target (double dispersion):
75L24 ACCURACY FOR SECOND BURST ON TARGET ATTEMPT
1000m target, 700m range estimate on first shot (30% error): 0%
1000m target, 800m range estimate on first shot (20% error): 0%
1000m target, 900m range estimate on first shot (10% error): 16%
700m target, 490m range estimate on first shot (30% error): 0%
700m target, 560m range estimate on first shot (20% error): 29%
The above data suggests that the low velocity 75L24 might be better used with bracketing on long range shots or with a large error on the first shot at any range, where the poor performance with Burst on Target is probably due to the extremely curved trajectory and relatively long time of flight
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At 1000m range the 75L48 APCBC single dispersion for 50% of shots is 0.6m vertical and 0.5m lateral. The distances to capture 68.3% of the shots is about 0.9m vert and 0.75m lat.Originally posted by Mr. Tittles:Think of Firing (DD or double Dispersion) as a good approximation of a second shot chance (gunner with training not stressed)... Especially at shorter ranges (not less than 500m where human factors can get excessive).
Dispersion might be understood as a 3rd shot chance for competant gunners that are in control.
Even a 75mmL24 could repeatbly hit a tank sized target after the third round at 1000m typically (and many tanks were larger than 2mx2.5m). After a BOT (burst on target), it could hit it almost continually! It is firing a spin stabilized massive hunk of metal. It isn't shooting spitballs with both eyes closed.
I understand that rexword is trying to get to some kind of first round fudge-about. But I think that unless similar data can be found for allied guns and the odd 75mmL48 data challenged, he may have some say in future patches/games from BTS.
PS I will reiterate my point made earlier. If you look at the 500m data, both are 100%. To me that means that Dispersion rounds are falling within 1 meter height delta. If we double that dispersion, then a 2m height delta still captures them. First round shots at 500m may certainly be influenced by many factors. It would not be a sure kill in any case.
The Germans assumed that on a battlefield the dispersion would be doubled due to out of perfect alignment guns, less than perfect gunners, etc.
So the 68.3% doubled dispersion distances would be 1.8m vertical and 1.5m lateral, and half of that is 0.9m vertical and 0.75m.
If 68.3% of the 75L48 APCBC shots at 1000m are up to 0.9m above or below the center of target aim point, and are up to 0.75m left or right of the center aim point, it is obvious that less than 100% will hit a 2m high by 2.5m wide target when the gun is aimed at 1000m range.
If one looks at the single dispersion situation, a first round hit might be due to a combination of an incorrect initial range estimate and random scatter that brings the round back onto the target. The second round could then miss, or the second round could hit and the third round might miss.
Nothing is 100% sure even if everything seems to have been done correctly, and random dispersion could mislead the gunner and commander into believing they had the correct range (when they didn't) or had a wrong range setting (when they were pretty good).
We created a computer program using random dispersion data and range setting inputs to see what a gunner would typically experience in terms of fall of shot on a series of shots, and ran the program over and over with different initial range estimates. Random dispersion messes things up, you think you're aiming high but the aim is near or on center, you hit the target but the aim is actually off the target.
Burst on Target is great in theory, but what if one cannot see where the round hits the ground in front of the target? How does one figure out which trajectory point to use on a high shot?
It is very difficult to tell what the trajectory height is at the point where the round just passes over the target tank. If one uses the maximum trajectory height that may be way off the mark. Remember, we're talking about rounds fired at targets 1000m away and the total flight time for 75L48 APCBC is less than 2 seconds.
If there are trees in back of the target and the tracer isn't observed too well for any number of reasons, burst on target goes out the window on high misses.
On low misses that bounce in the dirt or on the grass, the estimated height of the trajectory may be much lower at the target than where the round hit the ground, so one can be off on low misses too.
Burst on target is not a 100% surefire follow-up shot technique.
[ August 21, 2004, 09:40 AM: Message edited by: rexford ]
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British evidence shows that the Tiger 88mm L56 and the Flak 88mm L56 fired different APCBC rounds at least through late 1944. Tiger used small capacity round, 88mm Flak used large capacity round.Originally posted by Mr. Tittles:I find it difficult to believe that the Germans would not try to standardize the two applications of the 88mmL56 (no other vehicle used this weapon).
Tiger 88mm APCBC had 0.59% of weight as HE burster, 88mm Flak ammo had 1.65%.
German 75mm APCBC had 0.20% of weight as HE burster, one of the smallest percentages for a WW II armor piercing round with a burster.
88L71 APCBC has same percentage as Tiger round, 0.59%.
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Our book shows two 88mm Flak rounds at 9.54 kg, an early war version and a later war improved version:
"The 88mm Flak APCBC which fought the KV and T34 tanks during 1941 and early 1942 was less effective than the round fired by the Tiger E. A British firing report shows that the later 88mm Flak round with a large capacity HE burster (and 9.54 kg weight) penetrated 8% less than the Tiger E APCBC, but the above data shows about a 23% average inferiority for early 88mm Flak ammo."
Based on our research the Germans continued to produce the 9.54 kg Pzgr APCBC round for their 88mm L56 Flak units, and the Tiger used the slightly more effective Pzgr 39 APCBC ammo at 10.0 kg (Tiger APCBC has more penetration, due in part, to a smaller HE burster).
Our conclusions may be different from Mr. Jentz , since we have good reason to believe there was an improved Pzgr large HE capacity APCBC round fired by 88mm Flak units and the improved round was used by the British in their firing tests with German 75mm and 88mm APCBC ammo against oblique targets.
There is definite evidence of an improved Pzgr round, at around 9.6 kg, which shows up in many of the British documents that we have. Not just one report. And it appears that the improved Pzgr round was produced through 1944 and was not replaced with the 10 kg smaller HE capacity round fired by Tiger.
We've done quite a bit of research on the APCBC round fired by the Flak guns using British intelligence reports, data that the British captured from the Germans and British firing tests.
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It appears that the Germans still were using the 9.6 kg large capacity rounds in the 88mm Flak 36 guns during late 1944, which seems to be a fact.Originally posted by Mr. Tittles:I think the number of Tiger Is and 88mm Flak need to be considered. There were probably never more than a few hundred Tiger Is operational at most times. 88mm Flak were in the thousands. Granted many Flak guns were guarding cities, many were also in Army field Flak battalions.
My thought would be that there would be no need to continue producing a sub standard AP round. Both weapons would probably use the improved 88mm AP in the field. Any old AP would be relegated to home guard or other non-front units.
The British did not say that the Flak guns originally used Pzgr, then switched to Pzgr 39, and then were found using Pzgr.
There are many factors that lead to somewhat off looking WW II decisions which we are not aware of, and may never know much about.
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FIRST ROUND ACCURACY OF GERMAN TUNGSTEN CORE AMMO
This article looks at the basic ballistic characteristics of the German tungsten core APCR (Armor Piercing Composite Rigid) rounds, estimates first round hit probability against a 2m high by 2.5m wide target and compares APCR to APC and APCBC results.
APCR is a full caliber projectile which encloses a small, high density tungsten core penetrator in a light weight carrier.
The following table presents the hit percentages against a 2m high by 2.5m wide target when the aim is at the center of a stationary object with a known range, where misses are due to twice the firing trial random scatter: (source is German set of ballistic tables for tungsten core and other projectiles):
HIT PERCENTAGE AT A KNOWN RANGE
TUNGSTEN CORE AMMUNITION
DOUBLED DISPERSION
RANGE...50L60...75L48...88L56...88L71
100m..........100......100........100.......100
300m..........100......100........100.......100
500m............98........99........100.......100
700m............84........88..........95.........98
900m........................69..........87.........93
1100m......................52..........74.........85
1300m......................37..........63.........76
1500m......................25..........52.........66
1700m......................19.......................58
1900m......................14.......................50
Notes:
All rounds are later type tungsten core ammo , no arrowhead types
Misses due to doubled random scatter
Calculated by Germans from vertical and lateral scatter data
German ballistic tables provide data for 100m range increments
The 75L48 scatter beyond 700m is markedly inferior (wider spread) to both 88mm rounds., which is similar to the comparison of APCBC results.
The German APC and APCBC hit percentage at a known range against a stationary 2m by 2.5m target is presented for comparison purposes:
HIT PERCENTAGE AT A KNOWN RANGE
APC AND APCBC AMMUNITION
DOUBLED DISPERSION
RANGE...50L60...75L48...88L56...88L71
100m..........100......100........100.......100
300m..........100......100........100.......100
500m..........100......100........100.......100
700m..........100........92..........99.........97
900m.......... 98........75..........96.........90
1100m..........92........58..........90.........81
1300m..........81........44..........82.........71
1500m..........68........33..........74.........61
1700m......................24..........64.........53
1900m......................18..........56.........46
Notes:
50L60 firing APC, others fire APCBC
Misses due to doubled random scatter
Calculated by Germans from vertical and lateral scatter data
While the random scatter of the tungsten core ammo is greater and the hit percentages at constant aim are lower for 50L60, 75L48 and 88L56 rounds, the scatter pattern for 88L71 Pzgr 40/43 is smaller than the APCBC dispersion. (resulting in a higher hit rate).
Combining the scatter data with a 25% average range estimate error (bell shaped error curve) results in the following first round hit probabilities for German tungsten core ammo against a stationary 2m x 2.5m target:
FIRST ROUND HIT PROBABILITY BY TUNGSTEN CORE AMMO
25% AVERAGE RANGE ESTIMATE ERROR
RANGE...50L60...75L48...88L56...88L71
500m.......... 86........86.........88.........97
800m...........43........39.........48.........65
1100m.........18........16.........26.........38
1400m.......................8.........15.........22
Note:
Muzzle velocities are 1130 m/s for 50L60 and 88L71, and 930 m/s for 75L48 and 88L56
The following table presents the computed hit probabilities for the APC and APCBC ammo fired by the same guns against a stationary 2m x 2.5m target with 25% average range error:
FIRST ROUND HIT PROBABILITY BY APC AND APCBC CORE AMMO
25% AVERAGE RANGE ESTIMATE ERROR
RANGE...50L60...75L48...88L56...88L71
500m.......... 81........73.........81.........93
800m...........35........33.........39.........57
1100m.........17........15.........20.........32
1400m.........10..........7.........12.........18
Note: 50mm gun firing APC, others firing APCBC.
Although the accuracy of tungsten core ammo beyond close range is often downplayed due to the greater velocity loss with range compared to APCBC ammunition, the 75mm and 88mm guns are more accurate firing tungsten core due to the higher velocities and flatter trajectory.
The basis for the computed hit percentages against a stationary 2m by 2.5m target is a statistical analysis using the vertical and lateral scatter patterns obtained from firing tests. The 50% zone for the scatter follows (50% of scatter with a constant aim within the stated distance):
50% ZONES FOR VERTICAL AND LATERAL SCATTER
VERTICAL/LATERAL ZONE LENGTH FOR CONSTANT AIM
SINGLE VALUES OF DISPERSION
50L60 TUNGSTEN CORE
100m....0.05m/0.05m
300m....0.17m/0.16m
500m....0.30m/0.28m
800m....0.51m/0.49m
Note:
At 800m range, 50% of the rounds fired at a constant aim will be within a box that is 0.51m high and 0.49m wide, which corresponds to a vertical distance of 0.26m above or below the mean impact point and a lateral distance of 0.25m right or left.
50L60 APC
100m....0.03m/0.03m
300m....0.09m/0.09m
500m....0.15m/0.15m
800m....0.26m/0.24m
1000m..0.33m/0.30m
1300m..0.47m/0.41m
1500m..0.58m/0.50m
75L48 TUNGSTEN CORE
100m....0.1m/0.0m
300m....0.2m/0.1m
500m....0.3m/0.3m
800m....0.5m/0.4m
1000m..0.7m/0.6m
1300m..1.0m/0.8m
1500m..1.2m/1.0m
2000m..1.8m/1.5m
Note:
When only one decimal point is provided the figure has been rounded up or down. The actual figure may be up to 0.049m above or below the listed number.
75L48 APCBC
100m....0.1m/0.0m
300m....0.2m/0.2m
500m....0.3m/0.2m
800m....0.4m/0.4m
1000m..0.6m/0.5m
1300m..0.8m/0.7m
1500m..1.0m/0.9m
2000m..1.6m/1.3m
2500m..2.4m/1.8m
3000m..3.3m/2.3m
88L56 TUNGSTEN CORE
100m....0.1m/0.1m
300m....0.2m/0.1m
500m....0.2m/0.1m
800m....0.4m/0.2m
1000m..0.5m/0.3m
1300m..0.7m/0.4m
1500m..0.8m/0.5m
88L56 APCBC
100m....0.1m/0.1m
300m....0.2m/0.1m
500m....0.2m/0.2m
800m....0.3m/0.2m
1000m..0.4m/0.2m
1300m..0.5m/0.3m
1500m..0.6m/0.3m
2000m..0.9m/0.5m
2500m..1.2m/0.7m
3000m..1.7m/1.0m
Note:
The remarkable aspect of the Tiger 88mm firing APCBC is that 50% of the constant aim rounds at 1000m will be within 0.1m or 10cm (4 inches) right or left of the mean impact point, and equal to or less than 0.2m or 20cm (8 inches) above or below the average impact, after rounding to the nearest tenth of a meter. The Tiger rounds had unusual repeatability.
88L71 TUNGSTEN CORE
100m....0.0m/0.0m
300m....0.1m/0.1m
500m....0.2m/0.2m
800m....0.3m/0.3m
1000m..0.4m/0.3m
1300m..0.5m/0.4m
1500m..0.6m/0.5m
2000m..0.8m/0.7m
3000m..1.2m/1.0m
88L71 APCBC
100m....0.1m/0.0m
300m....0.1m/0.1m
500m....0.2m/0.2m
800m....0.4m/0.3m
1000m..0.5m/0.3m
1300m..0.6m/0.4m
1500m..0.7m/0.5m
2000m..0.9m/0.7m
2500m..1.1m/0.9m
3000m..1.4m/1.0m
3500m..1.6m/1.2m
4000m..1.8m/1.4m
Since the above data is for the 50% zone and is based on a bell shaped normal distribution curve, the following multipliers would be used to convert to other coverages:
50% zone includes half of the random scatter and equals the listed distance
68.26% zone equals 1.48 times the 50% zone lengths (68.26% is one standard deviation)
75% zone covers 1.71 times the 50% zone lengths
80% zone covers 1.90 times the 50% zone dimensions and includes 80% of shots
85% zone includes 2.14 times the 50% zone lengths
90% zone covers a distance 2.44 times as large as the 50% zone
95% zone covers 2.91times the 50% zone size
For double dispersion, the listed 50% zone dimensions would be doubled.
The Germans used the above 50% zone figures to compute the hit percentages against a 2m high by 2.5m wide target assuming constant aim at a known range. As an example of use we'll look at the case for an 800m shot by 50mm L60 APCR using doubled dispersion.
The doubled dispersion 50% zone for APCR at 800m is 1.02m high and 0.98m wide. Dividing the vertical target height of 2m by 1.02m equals 1.96 times the doubled 50% zone height. Dividing 2.5m by the 0.98m 50% zone width results in 2.55.
The above calculations result in vertical and lateral hit probabilities of 81.4% and 91.5%, which are multiplied together to obtain an overall hit percentage of 74% after rounding. The German ballistic table for 50L50 APCR presents a 74% hit chance against a 2m x 2.5m target at 800m with doubled dispersion and constant aim. It appears that the Germans used dispersion data with two decimal places when they calculated the hit probability against a 2m by 2.5m target even though they usually only show one decimal place in the tables.
The German ballistic tables which were used as a reference for this article contain trajectory information for APC, APCBC, APCR, HEAT and HE rounds, use 100m range increments and provide data for flight time, gun elevation, descent angle, 50% zones for vertical and lateral scatter and ground impact of round, velocity at range, maximum trajectory height and battlesight aim range against a 2m high target.
VELOCITY VS RANGE DATA FOR GERMAN APCR
RANGE..50L60..75L48..88L56..88L71
0m.....1130.....930......930......1130
100m...1074.....910......916......1116
500m....862.....832......863......1061
800m....717.....775......824......1020
1000m...........739......798........994
1500m...........651......736........928
RETAIN..........70%.......79%.......82%
Weight.1.07.....4.1...... 7.3.......7.3
Note:
Velocity in m/s
Weight refers to total projectile kg
RETAIN refers to percentage of muzzle velocity available at 1500m
VELOCITY VS RANGE DATA FOR GERMAN APC AND APCBC
RANGE..50L60...75L48....88L56......88L71
0m......835.....750......780.......1000
100m....809.....738......770........990
500m....707.....691......734........952
800m....636.....659......707........924
1000m...591.....637......690........906
1500m.. 491.....585......647........860
2000m...........536......607........815
3000m...........451......532........729
4000m....................................648
RETAIN..58%.....78%.......83%.......86%
Weight.2.06.....6.8......10.0......10.16
Note:
50mm round is APC, others are APCBC
RETAIN refers to percentage of muzzle velocity available at 1500m
The difference in velocity loss percentage at 1500m between APCR and APCBC rounds is less than -5% for 88mm ammo and is about -10% for 75mm APCR. The 75mm and 88mm APCR rounds also possess a higher velocity at 1500m than APCBC, which results in a flatter more accurate trajectory for APCR and contributes to a higher hit percentage.
MAXIMUM TRAJECTORY HEIGHT
APCR VS APC/APCBC AMMO
RANGE..50L60.....75L48....88L56...88L71
500m...0.3/0.5..0.4/0.6..0.4/0.5..0.3/0.3
800m...1.0/1.5..1.1/1.5..1.0/1.4..0.7/0.9
1000m..............1.8/2.5..1.7/2.3..1.1/1.4
1500m..............4.5/6.3..4.0/5.5..2.7/3.2
Notes:
Max trajectory heights in meters
Slash separates APCR/AP trajectory data
Applying a curve of best fit approach to the German base data for 0m to 1000m shots, the vertical and lateral 50% zones for 88L56 APCBC were estimated to two decimal places:
50% DISPERSION ZONES FOR 88L56 APCBC
VERTICAL AND LATERAL DISTANCES
RANGE…VERTICAL..LATERAL
100m………0.10m………0.09m
200m………0.13m………0.11m
300m………0.16m………0.12m
400m………0.19m………0.14m
500m………0.21m………0.15m
600m………0.24m………0.17m
700m………0.27m………0.18m
800m………0.30m………0.19m
900m………0.34m………0.21m
1000m...0.37m………0.22m
On constant aim shots at 1000m, half of the 88mm rounds would vary from the mean impact point by less than 7.3 inches vertically and 4.4 inches laterally during the firing tests (single dispersion).
It is worth noting that the muzzle velocities for German 75L48 and 88L56 APCR are lower than the corresponding velocities for the tungsten core rounds used by the Americans (76mm at 1037 m/s and 90mm HVAP at 1021 m/s) and Russians (76.2mm at 965 m/s and 85mm HVAP at 1050 m/s).
Even though the early arrowhead tungsten core rounds (APCR) had a relatively poor ballistic shape and sometimes became stuck in the barrel of German guns, the later war APCR appears to have possessed good ballistic characteristics and was more accurate than the 75mm and 88mm APCBC rounds.
[ August 21, 2004, 07:55 AM: Message edited by: rexford ]
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You obviously have not looked at the physics and optics problems that are involved.Originally posted by Mr. Tittles:I think the following need to be considered:
1. The device does NOT have to be fully splayed out to see stereoscopically. There are ample photos showing in use when it is not fully splayed out or strait up. In other words, why splay it out at all if not all the way?
2. The means of focusing the 3D image, whether fully splayed out or not, could be correlated to range. So if the same IPD was set and the operator learned the range of values that corresponded to ranges; he would have some means of determining range.
basically I see the SF (not TF) lengthening the abilities of the tank crewmen from sub 1000m to out to 2000m or so.
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"Firing tests show the expected percentage of projectiles that will hit a 2.5m × 2m target by a gunner during practice firing on a gun range. It is obtained by doubling the dispersion pattern obtained from the dispersion test data."
As noted in my previous post, the Germans first fired their guns and ammo against targets, then they analyzed the data statistically to determine the 50% zones.
Then they applied the 50% zone data to compute the hit % against a 2m x 2.5m target using single and doubled dispersion. That is the correct explanation of what the data means.
We have had the German ballistic tables with dispersion 50% zones and computed hit %'s against a 2m x 2.5m target for over twenty years, and have studied the heck out of the info.
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I guess you didn't read my earlier posts close enough. Suggest you go back to them and get up to speed on what I said.Originally posted by Mr. Tittles:No. The guns are aimed at a given range and the vertical and lateral dispersion patterns are measured and analyzed using statistics.
The German ballistic tables present the 50% zone for single dispersion, the vertical and lateral distances that capture 50% of the shots.
This differs from what the website says of course (Gus and Armor). I really doubt what rexfolk says.
I have the original German documents where the hit percentages against a 2m high x 2.5m wide target were estimated. The base data for the calculations is the 50% zone for vertical and lateral dispersion as measured on a firing range.
The firing range did not use a 2m x 2.5m target, so the estimated hit %'s against that target size are estimated. I have a British BIOS on the methods used to determine weapon and ammo dispersion zones, and they did not use a 2m x 2.5m target.
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The known range accuracy for 88mm Flak 18, 36 and 37 against a 2m x 2.5m target are (doubled dispersion):
500m, 98% (100%)
1000m, 64% (93%)
1500m, 38% (74%)
2000m, 23% (50%)
2500m, 15% (31%)
3000m, 10% (19%)
Quite a bit less than the Tiger 88 at most ranges (Tiger dispersion hit % in brackets).
The 88mm Flak fired a large HE capacity Pzgr APCBC round weighing 9.6 kg through November 1944, according to a British report I have (PRO holds the report by number WO 194/749). Tiger 88mm fired a smaller HE capacity APCBC round (Pzgr 39).
It is difficult to match the above stats for 88mm Flak rounds with a known range against the stories from North Africa where British crews would sometimes bail out if an 88mm Flak MISS came close, cause they were sure the next round would be on target.
Doubling the dispersion kinda kills the accuracy with a known range, and it is probable that the best crews were able to put their rounds in a consistent fashion closer to the intended aim point (a combination of better gun sight settings and good weapon alignment/maintenance would be needed here).
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Sit down and draw a picture of the stereoscopic range finder with arms horizontal. Horizontal angle that aligns vision is measured by turning dial, where calibration is based on distance between lenses.Originally posted by Mr. Tittles:Where exactly do you think this dial for pupil setting is?
Now draw the arms in periscope position, about 25cm apart, and note direction that lens will turn when dial is rotated. VERY DIFFICULT to focus device because angle which changes is no longer horizontal but is at a very odd angle.
And remember that due to the 25cm lens difference the accuracy and image sharpness is going to be seriously degraded.
If you draw the device in horizontal arm position and think about how the angle changes are related to the sight triangle needed to align the views, the great difficulty which follows from the periscopic position may be easier to understand.
The change in angle when the range dial is turned is perpendicular to the arm length, not perpendicular to the horizon or vertical.
There really is nothing more that can be said to explain what is going on short of posting a drawing of my own which illustrates the above noted situation.
Until someone comes up with a manual or document or explanation or something that shows how the TF 14 can be used for stereoscopic range measurement in periscope position, my view is that the physics of the situation makes that result (range measurements in periscope position) highly unlikely.
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I have a British reported dated November 18, 1944, where the 88mm Flak fires the 88mm Pzgr APCBC round at 9.6 kg. Report held by PRO as WO194/749, on German 75mm and 88mm APCBC against oblique armour.Originally posted by Mr. Tittles:http://gva.freeweb.hu/weapons/german_accuracy7.html
Footnotes
1. 8,8cm Flak 18, 36 & 37. Source: Jentz, Thomas L: Tank Combat in North Africa. Note that there is a significant difference in accuracy between the early Pzgr. and the later Pzgr.39 fired from the 8,8cm Kw.K.36. [up]
2. 8,8cm Kw.K.36. Source: Jentz, Thomas L: Germany’s Tiger Tanks. Tiger I & II: Combat Tactics. Although the 8,8cm Flak 18, 36 & 37 is ballistically the same as the Kw.K.36, the accuracy is specified only for the Kw.K.36 in the reference. It is likely that the accuracy for the 8,8cm Flak would be similar for these ammunition types. [up]
3. 8,8cm Kw.K.43. Source: Jentz, Thomas L: Germany’s Tiger Tanks. Tiger I & II: Combat Tactics. Although the 8,8cm Pak 43 and 8,8cm Pak 43/41 are ballistically the same as the Kw.K.43, the accuracy is specified only for the Kw.K.43 in the reference. It is likely that the accuracy for the 8,8cm Pak 43 and 43/41 would be similar. [up]
So it seems that the 88mm Pzgr APCBC fired by the Flak 36 was not just an early war round, but was being made for that gun through late 1944. Different APCBC were made for the 88mm tank guns.
While this is speculation, it seemed that the greater dispersion when the 88mm Flak fired, as opposed to the Tiger 88mm, might have due to the characteristics of the flak gun, which does not provide as stable a platform as a Tiger tank.
Or maybe the Tiger gun was just different enough to be much better.
The Pzgr round fired by the Flak 36 was a large capacity round with an extra large HE burster.
[ August 16, 2004, 01:19 PM: Message edited by: rexford ]
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Thanks for identifying the material and sources.Originally posted by Mr. Tittles:http://gva.freeweb.hu/weapons/german_accuracy7.html
Footnotes
1. 8,8cm Flak 18, 36 & 37. Source: Jentz, Thomas L: Tank Combat in North Africa. Note that there is a significant difference in accuracy between the early Pzgr. and the later Pzgr.39 fired from the 8,8cm Kw.K.36. [up]
2. 8,8cm Kw.K.36. Source: Jentz, Thomas L: Germany’s Tiger Tanks. Tiger I & II: Combat Tactics. Although the 8,8cm Flak 18, 36 & 37 is ballistically the same as the Kw.K.36, the accuracy is specified only for the Kw.K.36 in the reference. It is likely that the accuracy for the 8,8cm Flak would be similar for these ammunition types. [up]
3. 8,8cm Kw.K.43. Source: Jentz, Thomas L: Germany’s Tiger Tanks. Tiger I & II: Combat Tactics. Although the 8,8cm Pak 43 and 8,8cm Pak 43/41 are ballistically the same as the Kw.K.43, the accuracy is specified only for the Kw.K.43 in the reference. It is likely that the accuracy for the 8,8cm Pak 43 and 43/41 would be similar. [up]
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A whole lot of assumptions regarding the possible measurement of angle/range in the periscopic mode while the physics of the situation suggests that it can't be done.Originally posted by Mr. Tittles:A few sources support that the SF did not have to be all the way to see stereoscopic images. Most do state that the further apart they are, the more 3D the images appear (some describe the effect as people appearing to be sculpted). Its apparent then that since there IS just one knob that adjusts this stereo effect (maybe Rexford needs to go back and look again), and that knob does have markings which must be the range scale, there could be a way to correlate those knob readings to actual ranges. Ideally, it would be a linear correlation.
The combination of the clarity of image, depth of perception, graticle and knob readings makes me lean towards range finding with this device.
Someone posted accuracy data before from Spielberger for this device. I would not assume that would be for the end of the scale. It would probably be for the median values on the interpupillary distance.
Suggest that you reread my past posts and get up to speed on the physics and optics problems involved when a device designed for horizontal angle measurement with a range dial calibrated for horizontal arm distance has the arms close to vertical. With arms near vertical, the change in angle per dial turn is neither vertical or horizontal.
And I never said there were two knobs for stereoscopic range changes, just one. The other dial was for the pupil distance.
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No. The guns are aimed at a given range and the vertical and lateral dispersion patterns are measured and analyzed using statistics.Originally posted by Mr. Tittles:If I understand this correctly, the guns are put in a test fixture and fired so as to get the dispersion spread against a 2 x2.5 m target? Then this dispersion is doubled (in both height/width)?
The German ballistic tables present the 50% zone for single dispersion, the vertical and lateral distances that capture 50% of the shots.
I converted the 50% zones into 68% zones, and then calculated the hit % against a 2m high by 2.5m wide target using the twice the test results for lateral and vertical scatter pattern statistics. Vertical dispersion is usually greater than lateral dispersion.
Accuracy Data for 88mm Flak
in Combat Mission: Barbarossa to Berlin
Posted
wherefrom could someone get the idea that they could be interchanged ? Have you ever looked at the different cartridges ? It´s pretty clear that no FLAK 18/36/37 88/L56 could in any case exchange its ammo with the KwK 88/L56.
FLAK and KwK differed significantly in size and form of the chamber. They both had the same caliber length, but that does not mean they could exchange ammo.
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