Dispersion Angle for rapid fire WW2 aircraft guns

[HoHun]

Hi 2bighorn,

>Your definition of a mil wasn't used in ww2. That came later.

>ww2:
>mil equal to 1/1000 right angle, or 0.09° (5.4 moa)

>NATO after ww2:
>mil equal to 1/1600 right angle, or 0.05625° (3.375 moa)

Hm, that would of course overthrow my results for the US guns!

It would also invalidate my weapon dispersion table since it is based on the assumption that the historic dispersion would be expressed in identical units.

However, going back to the old thread, I found that two different definitions were used by the US in WW2, with one being 1/1000 of a right angle, and the other being 1/1000 of a radian, which is exactly the 0.0573° of the 1/1000 of range definition.

(The Germans used the fraction of range definition, too, and I would be suprised if the US weapons had that much more dispersion.)

So I'll continue to use the 0.0573° for now, but I'll keep my eyes peeled for an example where range and deviation are named in absolute figures so we can cross-check it!

Regards,

Henning (HoHun)

[Sable]

Originally posted by 2bighorn

During World War II the U. S. Army often used a mil equal to 1/1000 of a right angle, 0.1 grad, 0.09°, or 5.4 arcminutes.
One mil equals 1 foot at 1000' and 35' wingspan at 1000' equals 35 mils.

For example, outer ring on standard gunsight was 100 mils and inner ring was 50 mils, refective gunsight pipper itself was 2.5 mils or 5 mils, depends on gunsight.

So if we say:

a= size of object in feet
b= distance to object in feet
x= size of practice target or model in feet
y= mils
z= distance of practice target or model from viewer in feet

Then we can use 1000ft/b * a = y to determine the mils of the object we want to simulate, and then z/1000ft * y = x to determine the distance we need to place our model at from the viewer to simulate the object.

So if we use a Bf109, and a 1:48 scale Bf109 model then we know

a= 32.5ft (Bf109 wingspan)
b= 300ft (100yds)
x= .677ft or 8.125" (wingspan of 1:48 Bf109)


Then we can say 1000ft/300ft * 32.5ft = 108.3 mils

and

z/1000ft * 108.3 mils = .677ft

Z = 6.25ft

So we can say that a 1:48 scale Bf109 viewed from 6.25ft looks the same as a real Bf109 at 100 yards?  Does that math look right?

[HoHun]

Hi Crumpp,

>IIRC The US Military defines effective range as the point at which an average shooter can achieve 50% hit probability.

Thanks a lot! :-)

That's quite interesting because it fits very well with the US Navy idea of effective range being just beyond convergence range. As I pointed out above, you are not going to get more than 50% hits once the bullet streams from both wings start to diverge noticably, and if 50% was indeed the criterion, that would coincede with my explanation attempt.

Regards,

Henning (HoHun)

[2bighorn]

Originally posted by HoHun
Hi 2bighorn,
However, going back to the old thread, I found that two different definitions were used by the US in WW2, with one being 1/1000 of a right angle, and the other being 1/1000 of a radian, which is exactly the 0.0573° of the 1/1000 of range definition.

(The Germans used the fraction of range definition, too, and I would be suprised if the US weapons had that much more dispersion.)

So I'll continue to use the 0.0573° for now, but I'll keep my eyes peeled for an example where range and deviation are named in absolute figures so we can cross-check it!

Regards,

Henning (HoHun)

Yes, it gets confusing because of different definitions. Some ww2 documents have clear definitions of a mil, some don't.
Either way, values given by me were already calculated, so the differences in results are more or less differences in approach by USAF and Navy, like dispersion values for example.
On the other side, difference  in dispersion in mils by USAF (4 mils for .50) or by Navy (6-10) might be because of different mil definitions.
Taking off 30% from average Navy value of 8 would bring it down to 5.6 which better corresponds with USAF values. The rest might be contributed to stricter Navy standards.

[gripen]

Originally posted by Crumpp
In otherwords, you cannot prove it and do not have the documentation.

I have given the source ie thousands of ZU-23s around the world. If you want to check if my claims (or zorstorer's) are true, just go and check one.

Basicly the source is given it's up to your footwork to check it, normal academic procedure.

Originally posted by Crumpp
Say so and state it is a theory of your own making.

Actually if you examine the thread claimed by beet1e in the opening of this thread, it's me who showed to HoHun how to calculate probabilities of shooting.

And it's not my theory, just basic statistics.

Originally posted by HoHun  
Anyway, the result of complex random events is not an even distribution as the one in your original example, but one with a noticable peak around the average value, which - due to the marksman's efforts - is the position in the centre of the sight.

How a pilot, (marksman or novice) can aim in long range deflection shooting without systematical error if there is no way to determine correct aiming point?

gripen

[straffo]

Originally posted by gripen

How a pilot, (marksman or novice) can aim in long range deflection shooting without systematical error if there is no way to determine correct aiming point?

gripen

Because he is aiming with punctiform sight not considering the spread of the bullets.
And luckily this point is at the apex of the gauss curve

[Tony Williams]

A quote from the article on the .5" Vickers on my website, concerning the four-gun naval mounting:

"The four-barrel mounting had its guns adjusted to provide a spread of fire, amounting to 60 feet wide and 50 feet high at 1,000 yards (15-18 m at 915 m)."

That showed a touching if misplaced faith in the destructive capability of a .5" calibre bullet...

Tony Williams: Military gun and ammunition website and discussion forum

[Crumpp]

You calimed to have the manual and knowledge of a specific design detail of the ZU-23.  

Gripen says:
And the reason for the loosenes is actually described in the documentation.

You then admit you do not have specific design detail knowledge but are simply taking a guess.

Gripen says:
Generally I have no need to prove something in practice if I can prove it with theory.

And you admit you do not have access to the material in the first place when you made your calim.

Gripen says:
nd documentation is training material of Finnish army, not available in the net nor trough me.

And it's not my theory, just basic statistics.

It is your theory on the ZU-23.

All the best,

Crumpp

[gripen]

Originally posted by straffo
Because he is aiming with punctiform sight not considering the spread of the bullets.
And luckily this point is at the apex of the gauss curve

That is the situation in his example ie stationary target, no lead needed.

But I'm asking about the situation when some lead is needed (deflection shooting). Why the apex of the gauss curve should be the same as correct aim point then?

Originally posted by Crumpp

You calimed to have the manual and knowledge of a specific design detail of the ZU-23.

No, such claim I have not done. I have seen training material of Finnish army which states that (as well as our instructors BTW). And I do have knowledge on the ZU-23 because I served in the AA of the Finnish army and the ZU-23 was one of the weapons we got training for. I have put it to pieces and assembled it, I have done aerial shooting as well as ground target shooting with it.

Originally posted by Crumpp

It is your theory on the ZU-23.

Actually the theory has nothing directly to do with the ZU-23, the built in dispersion in it just utilizes theoretical fact that some amount of dispersion gives better probability of the hit as well as more hits if there is some error in aiming.

gripen

[Crumpp]

No, such claim I have not done.

Ok then you do not know.

Actually the theory has nothing directly to do with the ZU-23, the built in dispersion in it just utilizes theoretical fact that some amount of dispersion gives better probability of the hit as well as more hits if there is some error in aiming.

So far you have no shown one individual weapon which has "built in" dispersion.

All the best,

Crumpp

[Tony Williams]

Originally posted by Crumpp
So far you have no shown one individual weapon which has "built in" dispersion.

You could get different barrel clamps for the M61A1, which gave different dispersion patterns (including a wide one) by varying the spacing between the barrels. Don't know if that saw any use, though.

Tony Williams: Military gun and ammunition website and discussion forum

[gripen]

Originally posted by Crumpp
Ok then you do not know.

Hm... I do know what I learn during my service and I wonder why you try claim otherwise.

gripen

[Crumpp]

You could get different barrel clamps for the M61A1, which gave different dispersion patterns (including a wide one) by varying the spacing between the barrels. Don't know if that saw any use, though.

Hi Tony!

You got a link or documentation showing this was done specifically for the purpose of adding dispersion and not some other engineering purpose?

Hm... I do know what I learn during my service and I wonder why you try claim otherwise.

I guarantee you Gripen those pins are there for the exact same reason, ease of deployment or removal.  Although they add dispersion that is a flaw not a feature.

The ZAP 23 cannons have plenty of dispersion just due to the fact they are mass manufactured automatic weapons firing mass production ammunition.

The M2 is considered a very flat trajectory MG and very accurate.  It has a 4 mil dispersion cone.

All the best,

Crumpp

[straffo]

Originally posted by Crumpp
The M2 is considered a very flat trajectory MG and very accurate.  It has a 4 mil dispersion cone.

All the best,

Crumpp

sustened fire ?
what king of mounting ?

[Crumpp]

sustened fire ?

Yes.  I assume that is at max rounds per burst.  "Sustained" rpb is 10 rpb every 30 seconds for a maximum of 21 consecutive bursts.

Mounted in the wing of a P51D.

Picture hanger ever comes back up I can post a slew of documents on this subject.

All the best,

Crumpp