High Velocity AP round hit-zones

[Yoozername]

And it checks very well with the 'tripling of the 50%' data. At two sigma, they are the same. I should revise the graphic to show the zones.

But the normal distribution, and even my 'tripling of 50%', are assuming that things are conforming to math. It should be the other way around. The only real data to be had is the 50% data in the German documents. Where the other 50% land is not spelled out.

I have read that the Germans would take the horizontal and vertical components from each shot. That is, they measured how far away the shot landed away from the aimed point of impact. They probably added up the X data and Y data and divided by the number of shots. This is the data I would like to see.

I don't think a model that uses a 3 sigma approach is valid unless there is data to support it. As a educated guess, 2.5 sigma is more realistic.

[Mobius]

One wonders if they mean the dispersion box is 41" x 70" or the dispersion from point of aim is 41" by 70".

[Yoozername]

I was just looking at that data on lonesentry. Maybe a misprint? 1,200 yds?

[Mobius]

Looking at some of these old posts I find some where Lorrin is saying to use half the 50% dimensions to get the std. dev. and others where he says to use the full value. Today I changed my ballistics program to use 1/2 the 50% zone value and it no longer produces results that match firing range tests.

Per WO 291/180 live tests of the 17 pdr my ballistic program matched accuracy within 3% at 1000yd and 0.5% at 1500yds and 1% at 2000yds. That was one reason I chose his formula, because it produced realistic results. I think I'll go back to doing it the way it is written in his book not per the 2000 BF post.

[Yoozername]

I assume this is the data:

These are numbers collected by British Army Operational Research Sections during WWII (summarized in WO 291/180) Ranges are in yards, report indicates that the target is assumed to be a approximately the size of a Tiger Ie. Hit probability also assumes no crew error in line or range estimation.

Versus a Hull-Up static Target
6 pdr @ 500yrds…..100 percent chance of a First Round Hit (FRH: first round hit)
6 pdr @ 1000yrds…100 percent FRH
6 pdr @ 1500yrds…96 percent FRH
6 pdr @ 2000yrds…87 percent FRH

17 pdr @ 500yrds……100 percent FRH
17 pdr @ 1000yrds….100 percent FRH
17 pdr @ 1500yrds….100 percent FRH
17 pdr @ 2000yrds….98 percent FRH
17 pdr @ 2500yrds….93 percent FRH

Probability of a hit on first round, hull down static Tiger Ie sized target, assumed no error in line or range by crew.

Versus a Hull-down static Target
6 pdr @ 500yrds…..85 percent FRH
6 pdr @ 1000yrds…43 percent FRH
6 pdr @ 1500yrds…22 percent FRH
6 pdr @ 2000yrds…14 percent FRH

Versus a Hull-down static Target
17 pdr @ 500yrds…..88 percent FRH
17 pdr @ 1000yrds…51 percent FRH
17 pdr @ 1500yrds…29 percent FRH
17 pdr @ 2000yrds…18 percent FRH
17 pdr @ 2500yrds…12 percent FRH

[Mobius]

This part

[Yoozername]

Does that include ranging error??

[Mobius]

I assume they do as 'after first round' for the 17 pdr goes to 95% at 1000yds and 71% at 1500 yds. So if it was just dispersion there would be no change.

[Yoozername]

ORIGINAL: Mobius

I assume they do as 'after first round' for the 17 pdr goes to 95% at 1000yds and 71% at 1500 yds. So if it was just dispersion there would be no change.

I don't see that in the chart you posted.

[Mobius]

Ok, I edited the image.

[Mobius]

I don't like posting some of this research as the unique stuff always seems to end up over at the WOT forum.

[Yoozername]

So you are using data with ranging errors to check dispersion? I don't follow that at all.

Hopefully you can check my work and see if you agree.

The thread is actually in regards to using zone-fire to bypass these ranging errors. Perhaps this side discussion would be better in a separate thread?

[Mobius]

ORIGINAL: Yoozername
So you are using data with ranging errors to check dispersion? I don't follow that at all.

No. To check the final output. The dispersion is needed for the calculations but unless the formula produces real world results it's academic.

ORIGINAL: Yoozername
Hopefully you can check my work and see if you agree.
The thread is actually in regards to using zone-fire to bypass these ranging errors. Perhaps this side discussion would be better in a separate thread?

Give me some examples of guns with zones and I'll run the odds through my ballistics program.

[Yoozername]

WO 291/180
Do you have the conditions and methodology used in this report? What is the ranging error used? How many rounds were fired for each ranged test? What dispersion information is there? Basically you are saying that your program can achieve agreement with these two guns against TigerIe sized targets under the conditions tested? (stationary, hull up and down)

[Yoozername]

Give me some examples of guns with zones and I'll run the odds through my ballistics program.

Run the program for the conditions in the first post. That is, 75mmL48 firing APCR. T34/85 stationary face-on @300m. From 0-500 meters, what are the probabilities of being hit with 30% range estimation error in both directions (210m and 390m). If you could, explain how it's calculated in words if you do not want to reveal too much.

[Yoozername]

I found the report in an old post

WW2 hit probabilities
WO 291/180, Accuracy of anti-tank gunnery
Ranges in yards, target assumed to be Pz VI size.
Probability (%) of hitting static hull-up target with first round:
Gun OK for... 500 1000 1500 2000 2500
6 pdr line 100 100 96 87
range 87 33 13 3
both (hit) 87 33 12 3
17 pdr line 100 100 100 98 93
range 98 46 20 10 5
both (hit) 98 46 20 10 5
Probability (%) of hitting static hull-up target after first round:
Gun 500 1000 1500 2000 2500
6 pdr 100 86 59 41
17 pdr 100 94 71 50 36
Probability (%) of hitting moving target (direct-crossing at 15 mph) after first round:
Gun 500 1000 1500 2000 2500
17 pdr 86 48 26(e) 16
Probability (%) of hitting hull-down target with first round:
Gun 500 1000
17 pdr 59 18
Probability (%) of hitting static hull-down target after first round:
Gun 500 1000 1500 2000 2500
6 pdr 85 43 22 14
17 pdr 88 51 29 18 12
Comments and corrections
These values are those plotted on the graphs in the report; the value marked (e) is interpolated from
other data points. The overall shape of the fitted curves in each case is sinusoidal.
This report recommends that the maximum range of engagement for 6-pdr and 17-pdr ATk guns be
considered 800 and 1000 yards respectively. The criteria stated for maximum range of engagement for a
statically-sited ATk gun are:
50% chance of first-round hit on a static hull-up target;
90% chance of subsequent rounds hitting a static hull-up target;
50% hits on a hull-up direct-crossing target moving at 15 mph after MPI roughly corrected;
50% hits on a static hull-down target after MPI roughly corrected.
The first table clearly shows that errors in range have a much more important effect on accuracy than
errors in line.

[Mobius]

The block is using the unadjusted Bird-Livingston formula.
The range number is the target distance. The aim is the point of aim with error.
The P(Hit)% is the percent chance of hitting.
Firing height=7ft.

[Yoozername]

Is that 30% or 20%? Also, I believe a Hetzer had a 1 meter gun height



Example
Range 411
Aim 505

505-411=94m

94/411=0.2287

It looks like 22.9% over-range to me

[Mobius]

It's the way they handle the range error. It is the std deviation of the error. So 30% it would be 22.7%.

[Yoozername]

Most range error data just states +/- XX meters.

From the report WO 291/180...

These values are those plotted on the graphs in the report; the value marked (e) is interpolated from
other data points. The overall shape of the fitted curves in each case is sinusoidal.

I suppose that if it sinusoidal, it might look like this...