Dispersion data for KwK 42 L/70

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critical mass
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Re: Dispersion data for KwK 42 L/70

Postby critical mass » 21 Aug 2017 17:52

Firing table data reduced to standart deviation ranges for various late ww2 tank guns attached.
edit: 122mm is for BR-471B (APBC), 100mm is for BR-412B (APBC)
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Last edited by critical mass on 22 Aug 2017 12:04, edited 1 time in total.

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Mobius
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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 21 Aug 2017 18:41

critical mass wrote:Firing table data reduced to standart deviation ranges for various late ww2 tank guns attached.

In what plane is that data for? The 122mm data is essentially the values I have for horizontal std. dev. of 122mm BR-471. However, the 128mm PaK 80 seems to be an average of horizontal and vertical.

critical mass
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Re: Dispersion data for KwK 42 L/70

Postby critical mass » 21 Aug 2017 22:13

Both, dispersions in deflection and height for each gun are plotted with mean trend lines through their respective datapoints. In case of the 122mm D25T, the official FT data at 1000 and 2000m gave circular deviation patterns, resulting in uniform deviations in horizontal and vertical, thus creating a zero variance condition which requires that the mean trend curve went through the datapoints.
In variance to the official FT data for this gun, individual test data avaiable for the D25T point towards a larger dispersion in height than in deflection (as well as a more rapid raise in dispersion with range). However, test data have not been reproduced in this chart.
Similarely, ranges much closer than 800m haven´t been plotted due to the known importance of the mounting at close range in prevention of pointing errors firing a gun.

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Mobius
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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 21 Aug 2017 23:38

critical mass wrote:Both, dispersions in deflection and height for each gun are plotted with mean trend lines through their respective datapoints. In case of the 122mm D25T, the official FT data at 1000 and 2000m gave circular deviation patterns, resulting in uniform deviations in horizontal and vertical, thus creating a zero variance condition which requires that the mean trend curve went through the datapoints.

This official FT is not Table 3 of the DDR 122mm data is it? If it was table 4 it would not be circular at 2000m if it were pro-rated for range.

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Re: Dispersion data for KwK 42 L/70

Postby Yoozername » 21 Aug 2017 23:46

I'm sure most people know this pdf, but i will link it anyway

http://digitalcommons.unl.edu/cgi/viewc ... odmilintel

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Mobius
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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 22 Aug 2017 01:59

For the 122mm gun you may be referring to this pdf.
http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1164&context=usarmyresearch
This may show the incorrect Russian ballistics of 1944 that Miles mentioned. Notice the BR-471 with a muzzle velocity of 781 m/s takes only 2.7 seconds to reach 2000m.
But the DDR 1962 table BR-471 with a muzzle velocity of 781 m/s takes 3.0 seconds to reach that far. This is a discrepancy in ballistics.
http://www.panzer-war.com/Images/DDR-DSC01APC2.jpg

critical mass
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Re: Dispersion data for KwK 42 L/70

Postby critical mass » 22 Aug 2017 12:10

Official 122mm D25 FT, used for the plot:
http://tankarchives.blogspot.de/2013/08/d-25t-artillery-tables.html

BB (25% zone of deviation in height) BБ (25% zone of deviation in deflection)
BБ 1000: 0.30m; BB 1000: 0.30m
BБ 2000: 0.60m; BB 2000: 0.60m

resulting std deviations at 1000m: 0.44m & 0.44m
resulting std deviations at 2000m: 0.89m & 0.89m

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Mobius
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Re: Dispersion data for KwK 42 L/70

Postby Mobius » 22 Aug 2017 14:17

critical mass wrote:Official 122mm D25 FT, used for the plot:
http://tankarchives.blogspot.de/2013/08/d-25t-artillery-tables.html

That is probably a Cold War era FT table for a post WWII gun. (There is no date.) The WWII JS2 122mm had a MV of 781 m/s not 795 m/s.
I would pro-rate the data as in the following image.
122mmFTprorated.jpg
The deviation can not be exactly 0.6 at both 2000m and 2200m. These must be rounded numbers. So 0.6 would lie somewhere in between this range, near 2100m. Likewise 0.5 would lie near 1700m. So pro-rate 2000m from these marks gives something closer to 0.575.

They posted a series of these type FT on that site. But clues like the 85mm AP having a MV of 805 m/s when in WWII it was 792 m/s show things had changed.
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critical mass
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Re: Dispersion data for KwK 42 L/70

Postby critical mass » 22 Aug 2017 15:03

That´s fair and well, Mobius. The FT tables for BR471 AP and BR471B APBC and D25 gun are relevant.
However, I dealt only with official FT table data. Interpretation and reflection should be treated seperately. I do not intent to start a critique about present issues within the FT tables


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