Dispersion Angle for rapid fire WW2 aircraft guns

[Crumpp]

In ideal conditions (assuming that aiming was perfect and not systematically off) dispersion is bad. But in reality during WWII aiming was nearly allways systematically wrong because there was no way to determine correct lead until early gyroscopic sights arrived (and these still required some pure aproximations for range measurement). Basicly most pilots used too little lead and aiming point was behind and below correct point specially at long range. Therefore some amount of dispersion actually improved probability of the hit and also percentage of the hits.

While you are correct in this assumption Gripen for convergence adjustments, it does not improve the chances of achieving an immediate shoot down.

It is not correct for individual weapon dispersion.  Guns are designed to be as accurate as engineering allows and eliminate as much dispersion as possible.

More individual weapon dispersion simply means more chance to waste ammunition.

Ah rgr that. An army guy I used to know told me about how a belt fed machine gun was set up on the ground to provide cover for the guys moving behind it. Initially, it discharged over too small an area, so the rifling was adjusted (bored out?) to give the gun less accuracy but distribute the bullets over a larger area, which is what was needed in this case.

I would have to throw out the BS flag on this one, beetle.  

Think about the situation, if you were moving under covering fire wouldn't you want that fire to go exactly where the gunner aims?  Or at least as close as possible?

Covering fire is only effective if you are moving closely behind it.  From my experience you want it to be accurate as possible so that the gunner knows exactly where his bullets are going.  This ensures they do not go into you or anyone else they are not supposed too.

Additionally ask any soldier what would happen if he purposely bored out his weapons barrel or damaged his weapon.  The military uses terms like "statement of charges" and "Uniform Code of Military Justice" in the answer.

All the best,

Crumpp

[gripen]

Originally posted by Crumpp
The USAF maintained a .65% loss rate due to all enemy action causes.  

Hm... US forces lost thousands of planes (fixed wing and helicopters) in Vietnam, most of them to the AA, the ZU-23 being the one of the main weapons.

gripen

[gripen]

Originally posted by Crumpp
While you are correct in this assumption Gripen for convergence adjustments, it does not improve the chances of achieving an immediate shoot down.

More hits, better chance to shoot down.

Originally posted by Crumpp
Guns are designed to be as accurate as engineering allows and eliminate as much dispersion as possible.

Some succesful guns are designed with some dispersion built in.

Originally posted by Crumpp
More individual weapon dispersion simply means more chance to waste ammunition.

No, some amount of dispersion increase probability of the hit as well as amount of hits in the deflection shooting.

gripen

[2bighorn]

Originally posted by HoHun
Interesting data point! :-) That would be a 100% dispersion circle of roughly 7.6 mil. For which type of mount is this data valid?

Wing mounted various Navy AC types. I guess they took middle value of 8 mils (hit percentage was actually 13+, I rounded the value), since they stated dispersion values from 6 to 10 mils.

Originally posted by HoHun
For my example, I'm using 4 mil for the P-38 and 6 mil for the P-47, which is a bit lower, but seems to match historical data from various sources.

Interesting how AF and Navy got different numbers.

Originally posted by HoHun
Well, banner shooting was not from the dead six position against a stationary target, but involved dynamic pursuit-curve attacks and lead estimation, so the level of difficulty is considerably higher than in my example.

True.
However, I still believe that disabling enemy plane at 800 yds with .50 cals was extremely difficult. I'm not saying it didn't happen, it's just that probability is very low.

Here in AH I get often kill with 70-80 degrees deflections shots at 400-500 yds. Even with all the practice, it seems too easy.

[Crumpp]

Hm... US forces lost thousands of planes (fixed wing and helicopters) in Vietnam, most of them to the AA, the ZU-23 being the one of the main weapons.

Sure they did but they had tens of thousands of aircraft flying and rotating through the war zone over the decades the Vietnam war was fought.

Proportionally AAA is not very effective.  Certain tactics make it a neglible threat.  It is certainly much more dangerous to be the AAA gunner than the aircraft pilot in modern war.

Most of the Ground fire casualties appear to be Helicopters.  I seriously doubt the NVA were hauling 23mm systems through the jungle.  Most likely these are just MG's from fairly close range on a pretty much stationary helicopter landing or taking off.

You have any documentation on the ZU-23 being the main weapon used?  IIRC the North Vietnamese employed a variety of AAA systems with a PK and DSHK being the most common.

All the best,

Crumpp

[Crumpp]

However, I still believe that disabling enemy plane at 800 yds with .50 cals was extremely difficult. I'm not saying it didn't happen, it's just that probability is very low.

I think that is a very true statement.  The vunerability reports, convergence charts, and dispersion patterns seem to point to that conclusion.

More hits, better chance to shoot down.

No one is arguing that Gripen.  Your statement that weapons have design purpose dispersion is not correct.

Additionally, a projectile has to capable of inflicting enough damage to a vulnerable area of the target.  The chances of randomly achieving the required number of hits from a .50 cal or below on a vulnerable area are pretty slim.

Some succesful guns are designed with some dispersion built in.

Name them.

All the best,

Crumpp

[gripen]

Originally posted by Crumpp

You have any documentation on the ZU-23 being the main weapon used?  IIRC the North Vietnamese employed a variety of AAA systems with a PK and DSHK being the most common.

http://www.ausairpower.net/TE-Helo-Mar-05-P.pdf

"After the Vietnam experience
where thousands of UH-1/AH-1 family helicopters
were lost to a combination of AK-47/AKM rifles, ZPU, ZU-23
and ZSU-23-4P guns and MANPADS, the US embarked on a
major rethink of helicopter design."

Note that the gun itself is same in the ZU-23 and ZSU-23-4.

Originally posted by Crumpp

Your statement that weapons have design purpose dispersion is not correct.

The ZU-23 is designed with built in dispersion and for a rational reason.

gripen

[Crumpp]

After the Vietnam experiencewhere thousands of UH-1/AH-1 family helicopters were lost to a combination of AK-47/AKM rifles, ZPU, ZU-23
and ZSU-23-4P guns and MANPADS, the US embarked on a
major rethink of helicopter design."

Hardly proof of the Zu-23's effectiveness.

The ZU-23 is designed with built in dispersion and for a rational reason.

Yes, you have claimed this earlier.  And I replied that I doubted the dispersion was "built in" to increase hit probability.  More likely the mount is flexible to reduce the force of recoil so that it does not crack the mount.

All the best,

Crumpp

[gripen]

Originally posted by Crumpp
Hardly proof of the Zu-23's effectiveness.
 

http://www.globalsecurity.org/military/library/report/1984/CSJ.htm

" What can be seen can be hit."  For attack helicopter
pilots these words suddenly had real meaning in 1973.  The
event that gave meaning to these words was the 1973 Mid-East
War; the weapon was the ZSU-23-4.  During that conflict,
nearly one-half of all the aircraft that the Israeli forces
lost were to the ZSU-23-4.1  The significance of that
accomplishment was not lost on the attack helicopter com-
munity.  No single event has had such a profound effect on
the tactics of the AH-1.
     The ZSU-23-4 is the backbone of a Soviet maneuver
echelon's formidable air defense system.  Although it first
appeared in the mid-sixties, it was not until the 1973
Mid-East War that the ZSU's capabilities became widely known
and appreciated.  It immediately became apparent that the
ZSU-23-4 was a deadly threat to any low flying helicopter
that came within its sight and range.  This disconcerting
development quickly became a source of concern to attack-
helicopter pilots who had previously enjoyed a relatively
free rein during the Vietnam conflict.  As a result of that
concern, radical changes in tactics and increased emphasis
on survivability equipment evolved."

Originally posted by Crumpp
Yes, you have claimed this earlier.  And I replied that I doubted the dispersion was "built in" to increase hit probability.  More likely the mount is flexible to reduce the force of recoil so that it does not crack the mount.

It's 100% certainly built with loosenes in the support points to give some amount of dispersion. Go and check one.

gripen

[zorstorer]

Originally posted by gripen
http://www.globalsecurity.org/military/library/report/1984/CSJ.htm

" What can be seen can be hit."  For attack helicopter
pilots these words suddenly had real meaning in 1973.  The
event that gave meaning to these words was the 1973 Mid-East
War; the weapon was the ZSU-23-4.  During that conflict,
nearly one-half of all the aircraft that the Israeli forces
lost were to the ZSU-23-4.1  The significance of that
accomplishment was not lost on the attack helicopter com-
munity.  No single event has had such a profound effect on
the tactics of the AH-1.
     The ZSU-23-4 is the backbone of a Soviet maneuver
echelon's formidable air defense system.  Although it first
appeared in the mid-sixties, it was not until the 1973
Mid-East War that the ZSU's capabilities became widely known
and appreciated.  It immediately became apparent that the
ZSU-23-4 was a deadly threat to any low flying helicopter
that came within its sight and range.  This disconcerting
development quickly became a source of concern to attack-
helicopter pilots who had previously enjoyed a relatively
free rein during the Vietnam conflict.  As a result of that
concern, radical changes in tactics and increased emphasis
on survivability equipment evolved."

 

It's 100% certainly built with loosenes in the support points to give some amount of dispersion. Go and check one.

gripen

CC Grippen....

I can only speak about my time in the Army as a gunner in a M2A2 ODS Bradley.  The 25mm M242 Bushmaster chaingun had a built in flexability in the mounting.  This was done (as told to me by our master gunners) to aid in supression of the enemy and our secondary ability (anti-air).  If anyone remembers seeing the AH-64 attack on the guy under the truck you can see the circular pattern that the 30mm shells make (the M242 was designed as a smaller version of the AH-64's cannon).  That being said I only found that firing at a stationary target at 1500m my grouping was usually less than 3ft.  Not sure what you number crunchers out there can make of it  I'll try to dig out some pics.

[Squire]

Big difference between the campaign in the North vs fixed targets and the missions flown in the south. Crew served weapons were not a big part of the VC or NVA arsenal in S. Vietnam, at least, not prior to 1973.

I have seen several books on the percentage of hit in 1972 for SA-2s and 57mm and 85mm AAA guns, and it would seem the AAA guns are actually more effective, and less costly, over the long run, when deployed in large #s.  

Of course that changes over time, with technology, but its interesting to note that many of the Coalitions losses suffered in 1991 were as a result of "blind fire" AAA, and not the very expensive, and vulnerable SAM systems that so many governments spent billions on.  

The SA-6s in 1973 (Arab-Israeli), had a "sweet time" where they were a novelty. A mobile, high end SAM system. After countermeasures technology started coming into its own, and tactics changed, they were reduced in effectiveness greatly. In the 1982 Bekaa Valley campaign, they were taken out completely.

As for the ZSU-23-4 gun system, again, its impressive untill you jam it with countermasures, and its radar cant lock on to targets. Then its just a big target on tracks. To a UH-1 with no countermeasures im sure its a dangerous foe, but things change. Same with shoulder fired I-SAMs, they scare commercial airline pilots, not attack pilots. I think during the Falklands war a stinger managed to down a single Pucara turboprop...  

Since 1973, SAMs have not delivered the goods. They promise much and often fall short. Just an observation. Im not saying they dont belong in militaries, just pointing out they have not done nearly as well as advertised.

[Crumpp]

It's 100% certainly built with loosenes in the support points to give some amount of dispersion. Go and check one.

I have seen plenty of them Gripen.

The ZU-23 is a large caliber gun on a very light mount.  When it is fired, the weapon jumps around considerably.  

Yes the looseness of the mount adds dispersion.  It was NOT designed to add dispersion.

It is a flaw not feature when it comes to accuracy.  It my very well be an engineering feature designed to mitigate other parameters.

Show some documentation proving this was a "design feature" to add dispersion.  You said you had it.

Notice the definition of Ballistic Dispersion:

BALLISTIC DISPERSION— The variation of a path of a bomb or projectile which is attributed to physical tolerances in the weapon dimensions and to the stability of the weapon. The error produced by this variability is commonly stated as standard deviation in range and deflection of the error with respect to the mean point of impact.

Notice it does not say "the feature" produced.

http://www.fas.org/irp/doddir/usaf/afpam14-210/part14.htm

Employment Of The AH-1T (Tow) Against The ZSU-23-4
CSC 1984
SUBJECT AREA Strategic Issues
                     EMPLOYMENT OF THE AH-1T(TOW) AGAINST
                                 THE ZSU-23-4
                                 Submitted to
                                  Dr. Berens
                    In Partial Fulfillment of Requirements
                           for Written Communication
                  The Marine Corps Command and Staff College
                              Quantico, Virginia
                            Major S. J. Cobain, Jr.
                          United States Marine Corps
                                 April 6, 1984
            EMPLOYMENT OF THE AH-1T(TOW) AGAINST
                        THE ZSU-23-4
                           Outline
Thesis Sentence:  The AH-1T(TOW) is well suited to counter
                  the ZSU-23-4 on the modern battlefield.

I think that is a true statement borne out by experience in Vietnam, Aghanistan, and Iraq.

http://www.globalsecurity.org/military/library/report/1984/CSJ.htm

All the best,

Crumpp

[Crumpp]

The 25mm M242 Bushmaster chaingun had a built in flexability in the mounting.

Whoever told you that fed you some BS.  Sounds cool though.

The M242 needs 12mm of recoil movement in order to cycle the gun.  The mount is flexible to allow the gun to move that 12 mm.  

Served quite a few years in Uncle Sugar's Ain't Released Me Yet....

Check FM 3-22-1.

All the best,

Crumpp

[zorstorer]

Originally posted by Crumpp
Whoever told you that fed you some BS.  Sounds cool though.

The M242 needs 12mm of recoil movement in order to cycle the gun.  The mount is flexible to allow the gun to move that 12 mm.  

Served quite a few years in Uncle Sugar's Ain't Released Me Yet....

Check FM 3-22-1.

All the best,

Crumpp

CC it does need the 12mm of recoil movement to the rear to allow the gun to cycle.  If it doesn't the gun knows that a round didn't fire and stops the firing cycle.  BUT this recoil is to the rear, inline with the barrel.  The play I am taking about is in the mounting pins on the bottom front of the mounting.  You know the one you tore up your hands trying to release

So were you a crunchy when you were in?  

[Tony Williams]

Whether SAMs or AAA shoot many planes down isn't necessarily the issue. What does matter is that their existence makes the job of pilots much harder, forcing them to adopt tactics which reduce their ability to attack the targets they're after. So they can be effective even if they shoot nothing down.

Of course, if there's a big technology imbalance between attacker and defender, the pilots can overcome this - to some extent - with SEAD. Even so, that doesn't work against manually aimed guns like the ZU-23 (as opposed to the ZSU), which remain a serious threat to low-flying helos in particular. After all, if a burst of small arms fire can force an entire unit of AH-64s to retreat in disarray, think what ZU-23s could have done to them...

Tony Williams: Military gun and ammunition website and discussion forum