Dispersion data for KwK 42 L/70

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Ulater
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Dispersion data for KwK 42 L/70

Postby Ulater » 04 May 2017 17:46

Does anybody know the particular values for this gun? I would be itnerested in knowing how accurate it exactly was.

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Re: Dispersion data for KwK 42 L/70

Postby Christian Ankerstjerne » 04 May 2017 21:57


Ulater
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Re: Dispersion data for KwK 42 L/70

Postby Ulater » 04 May 2017 22:07

I am aware of that one. I was looking for some horizontal and vertical dispersion, so I can compare it to other guns.

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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 04 May 2017 23:07

I found this a long time ago.
(it's a maximum error, not 50% dispersion, for 50% dispersion divide this by 3):
Tiger 88L56 0.60 m at 1000m .
Panther 75L70 0.60 m at 1000m .

But the numbers for the 88mm don't match those found elsewhere so i wouldn't count on the 75mm being correct.
It is however a starting point. If you work the accuracy numbers back to the dispersion you will get reasonably close. The problem is I tried it and for every range over 1000m they seem to grow quite a bit.

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Re: Dispersion data for KwK 42 L/70

Postby Ulater » 04 May 2017 23:15

But the numbers for the 88mm don't match those found elsewhere so i wouldn't count on the 75mm being correct.
It is however a starting point. If you work the accuracy numbers back to the dispersion you will get reasonably close. The problem is I tried it and for every range over 1000m they seem to grow quite a bit.


Ah yes, mean dispersion, thats another thing I dont get, since I dont know how does one convert mean to 50% and/or back.

Thats why I hoped that somebody would know about some book simillar to WW II Ballistics, but with a unified criteria for accuracy.

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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 05 May 2017 10:40

I also found this:
German extreme dispersion 2000m
1.75 w x 1.5h 2187yd
75mm/L70 69" / 59"

With this I can deconstruct the accuracy table if I keep the width to height ratio the same.
If it changes with range then all bets are off.
So this is the result:
...............................my calculation.................table
Range.......w /h.........dispersion/action.........dispersion/action
1000m___0.338/0.29______=100/96.8__________>100%/97%
1500m___0.563/0.484____ =98.6/72.4_________ >100%/72%
2000m___0.79/0.68______ =92.1/48.5__________>92%/49%
2500m___1.114/0.955_____=73.3/28.6__________>73%/29%
3000m___1.44/1.23_______=55.1/18.4__________>55%/18%

So pretty close. Though the extreme dispersion snipped is probably from some British W.O. document so the whole exercise may not match the German firing table at all.
Here is the Rheinmetall conversion table to convert mean average to standard deviations and 50%.
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Last edited by Mobius on 05 May 2017 12:58, edited 1 time in total.

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Re: Dispersion data for KwK 42 L/70

Postby Ulater » 05 May 2017 10:58

German extreme dispersion 2000m
1.75 w x 1.5h 2187yd
75mm/L70 69" / 59"


Where have you found this?

So this is the result:
.................................calculation.................table
Range.......w /h.........dispersion/action.........dispersion/action
1000m___0.338/0.29______=100/96.8__________>100%/97%
1500m___0.563/0.484____ =98.6/72.4_________ >100%/72%
2000m___0.79/0.68______ =92.1/48.5__________>92%/49%
2500m___1.114/0.955_____=73.3/28.6__________>73%/29%
3000m___1.44/1.23_______=55.1/18.4__________>55%/18%


So If I understand it right the dispersion is for example 0.338 m horizontally and 0.29 vertically at 1000 meters?

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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 05 May 2017 11:51

Ulater wrote:
German extreme dispersion 2000m
1.75 w x 1.5h 2187yd
75mm/L70 69" / 59"

Where have you found this??

I don't have a source for that. I just saved it when I saw it posted. It was many years ago so the site may not exist any more.
Many sites don't allow posting of images so who ever posted it had to copy it to text.

So If I understand it right the dispersion is for example 0.338 m horizontally and 0.29 vertically at 1000 meters?
Correct.

One thing is it doesn't look like "extreme" is 3 times the 50% zone value. 1.75/.79 and 1.5/.68 does not = 3x.
It is closer to 2.44 times which is exactly the 90% zone.

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Re: Dispersion data for KwK 42 L/70

Postby Yoozername » 05 May 2017 16:46

viewtopic.php?f=70&t=227062

I suppose Miles post could be used?

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Re: Dispersion data for KwK 42 L/70

Postby Ulater » 05 May 2017 22:27

viewtopic.php?f=70&t=227062

I suppose Miles post could be used?


Hmm, is there a similar firing table for KwK 42 ?

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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 06 May 2017 13:39

Ulater wrote:Hmm, is there a similar firing table for KwK 42 ?

There should be, but it hasn't been posted on the net yet.
The fact that:
1.75 w x 1.5h 2187yd
75mm/L70 69" / 59"

exists Indicates that the British may have had a copy and translated and converted it to British units to compare with their own guns. Because 2187 yds is not a typical British test distance. Maybe if no German copy exists a British Report with the data languishes in W.O. records.
Last edited by Mobius on 06 May 2017 15:42, edited 1 time in total.

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Re: Dispersion data for KwK 42 L/70

Postby Yoozername » 06 May 2017 15:22

My basic premise is that IF you accept the German methodology as explained by Miles, then we can interpolate the data and compare the FT from one gun to another.

An example would be...

http://www.panzerworld.com/7-5-cm-kw-k-42-l-70

@1000m,both AP and HE have a 100% (97%) chance of a hit. If we look at the 7.62 cm Pzgr Rot @ 500 m, we see 100% (92%). It is 100%(100%) at 400m. Interpolating between the ranges, i.e. 450m, we would get 0.35m/0.25m. Somewhat in agreement with...1000m___0.338/0.29______=100/96.8__________>100%/97%

As anecdotal 'evidence', the British did use a Panther (Cuckoo) and it was hailed as a great way to get HE in windows at range. FWIW.

Edit:
1.75 w x 1.5h 2187yd
75mm/L70 69" / 59"

Would you expect the height to be tighter than the width?

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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 06 May 2017 15:53

Yoozername wrote:Would you expect the height to be tighter than the width?

No. Not at 2000m.
I think I've only seen one German firing table where the dispersion was more in the width than the height and that was at under 2000m or so. Mostly the vertical dispersion grows faster than the lateral dispersion. Though often in Russian firing tables the lateral is equal to or more than the vertical for some reason. I don't know why.

I was really surprised that it could be solved with values at the 7/6 ratio. It shouldn't have worked out at that ratio all the way to 3000m.

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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 08 May 2017 13:52

One gun that does have width deviation larger than height is the Pak 128mm. So it does happen.
viewtopic.php?f=47&t=220123

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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 01 Jun 2017 17:58

The graph below illustrates the deviation of 75mm/L70 KwK (assuming my number are valid) and some other guns.
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