[REPORTED]Gun Dispersion

[Aries144]

Has gun spread/accuracy been examined by the team yet?

 

Has Belsimtek reviewed the issue and made a determination? I know they're probably loaded with work, but it's a bit of a glaring issue. The current modeling really doesn't reflect the Northrup document for gun accuracy.

 

If lack of an original source for what a "mil" equates to is an issue (it's surprisingly hard to find!), I'm including a link to a US military sniper's manual that states that 1 mil is equal to 1m diameter at 1000m (or 10cm diameter at 100m, 50cm at 500m, etc). The relevant information is in the paragraph and picture on page 43.

 

Currently, the F-5's gun spread is about 30-40 mil (equivalent to a 300-400cm diameter group at 100m). According to the Northrup document, 80% of shots should fall in an 8 mil area (equivalent to a 80cm diameter group at 100m).

 

 

 

I hope this information is helpful!

Edited May 12, 2017 by Aries144

[LazerPotatoe]

"Hi guys!

We will examine this issue in detail and correct the problem.

Many thanks."

https://forums.eagle.ru/showthread.php?p=3030394#post3030394

[johnv2pt0]

That post was 4 months ago...hardly seems to a laymen that it should take that long to fix. Kind of feels like they are just allocating their time elsewhere which is very frustrating. I love their products but it seems like there are things on each of their modules that they simply never go back to fix.

 

It's weird that gun accuracy has been an issue on both the American jets and not on the 15...

[cicimicikiller]

Any news? It feels like I am throwing gravel on the opponents.

[Aries144]

Perhaps we aren't providing some piece of information Belsimtek needs to address this issue?

 

Belsimtek Devs, you let us know what info you lack and we'll do our best to find and provide it. :)

[dimitrischal]

I must be the only one who finds the spread useful in a2a combat?

 

I admit it's not as useful on ground targets but it kinda makes aerial gunnery easier than laser like precision and honestly I can't see how this can be considered a disadvantage.

I think of it like a shotgun vs a rifle situation and here the shotgun is the more useful instrument.

Just my opinion though....

[cicimicikiller]

I must be the only one who finds the spread useful in a2a combat?

 

I admit it's not as useful on ground targets but it kinda makes aerial gunnery easier than laser like precision and honestly I can't see how this can be considered a disadvantage.

I think of it like a shotgun vs a rifle situation and here the shotgun is the more useful instrument.

Just my opinion though....

 

Maybe if fire rate was higher then yes, but now it feels to me more like disadvantage. I prefer one well aimed burst instead of spraying enemy.

[dimitrischal]

Maybe if fire rate was higher then yes, but now it feels to me more like disadvantage. I prefer one well aimed burst instead of spraying enemy.

 

As they said in ww2 if you find the performance of you gun ineffective get closer.

With no modern targeting equipment I believe this is the only way to gunfight on the Tiger.

Of course I would like accurate performance of the guns and this matter resolved though.

[cicimicikiller]

Well, you have radar gunsight with range indicator, but i think you still need to get closer.. It's not like it's unplayable like this, as you said, just get closer, but sometimes that's easier said than done.

[Exorcet]

I must be the only one who finds the spread useful in a2a combat?

 

I admit it's not as useful on ground targets but it kinda makes aerial gunnery easier than laser like precision and honestly I can't see how this can be considered a disadvantage.

I think of it like a shotgun vs a rifle situation and here the shotgun is the more useful instrument.

Just my opinion though....

 

There is a point where the spread becomes too much, although I've gotten a lot more used to DCS F-5's gun than I was in the beginning. I don't think a tighter spread will pose many problems. As long as you can rely on your gun sight, a fairly accurate cannon should be fine. It will let you shoot at longer ranges and conserve ammo.

 

Ultimately it's about fidelity though. If the gun is not true to reality, it should be changed.

[johnv2pt0]

I must be the only one who finds the spread useful in a2a combat?

 

I admit it's not as useful on ground targets but it kinda makes aerial gunnery easier than laser like precision and honestly I can't see how this can be considered a disadvantage.

I think of it like a shotgun vs a rifle situation and here the shotgun is the more useful instrument.

Just my opinion though....

 

Problem is that with a shotgun all the shot gets to the same point at basically the same time. This isn't the case with the tiger. So while it may look like a shotgun from your perspective in the cockpit it's in reality nothing like it.

 

I think someone's already proven that by the books the dispersion should be around 8 mils and currently it's more like 40. This is a huge problem and pisses me off every time I get in the f-5.

 

I love this jet and the gun really bums me out. If you have to get so close that you risk flying through the debris of your opponent something's wrong. I hope it gets fixed soon.

[Aries144]

So, I just looked in the files and found that the M61 Vulcan, GAU-8 Avenger, and M39 guns have 3x - 4x larger dispersion than the other aircraft guns in the game.

 

The Mig-29/Su-27 gun is 0.0005 while the F-15 and F-5's guns are 0.0022. The Su-25's gun is set to 0.0005 and the A-10's GAU-8 is set to 0.0017. It appears to correspond to mil. 0.0005 would be 5 mil while 0.0022 would be 22 mil, etc.

 

I'd really like to hear ED or Belsimtek's reasoning for these decisions. Is it a matter of compensating for some imbalance elsewhere? Gameplay? Based on some sources other than manufacturer's data?

[Sarge55]

Just getting back into the F-5 and was wondering did this issue get sorted out?

[Angus]

So, I just looked in the files and found that the M61 Vulcan, GAU-8 Avenger, and M39 guns have 3x - 4x larger dispersion than the other aircraft guns in the game.

 

The Mig-29/Su-27 gun is 0.0005 while the F-15 and F-5's guns are 0.0022. The Su-25's gun is set to 0.0005 and the A-10's GAU-8 is set to 0.0017. It appears to correspond to mil. 0.0005 would be 5 mil while 0.0022 would be 22 mil, etc.

 

I'd really like to hear ED or Belsimtek's reasoning for these decisions. Is it a matter of compensating for some imbalance elsewhere? Gameplay? Based on some sources other than manufacturer's data?

 

 

Source wikipedia , M61 (F15C) as 8 mils so should be 0.0008 , A10C 5 mils = 0.0005 and not 0.0017. GAU8 shots must be in 20 feet circle at 4000 feets , it is not the case in DCS . :smilewink:

[cicimicikiller]

Still not fixed

[dimitriov]

Wikipedia talks about an ideal situation where the gun is grounded with no wind, and without any recoil. You are using it aboard a maneuvering airframe at 300 to 500 knots, which induces a far higher relative wind, higher recoil issue, and with an angled target aspect. This could explain the dispersion. So it may be IRL better than what you have ingame, but surely not like on the wikipedia page, which is, btw, a banned source for all developers. (Not fanboying or else, simply sounds pretty logical to me).

 

Nicolas

Edited September 30, 2017 by dimitriov

[johnv2pt0]

Wikipedia talks about an ideal situation where the gun is grounded with no wind, and without any recoil. You are using it aboard a maneuvering airframe at 300 to 500 knots, which induces a far higher relative wind, higher recoil issue, and with an angled target aspect. This could explain the dispersion. So it may be IRL better than what you have ingame, but surely not like on the wikipedia page, which is, btw, a banned source for all developers. (Not fanboying or else, simply sounds pretty logical to me).

 

Nicolas

 

It's wrong and I think has been conclusively shown in threads already. Here's an example of f-5 strafing runs. Compare this to in game tests and it's painfully obvious the gun dispersion in DCS is too great.

 

[Aries144]

Wikipedia aside, 8 mil 80% is the value from Northrup for the F-5's M39 guns, and 5 mil 80% is the value from multiple official sources for the A-10's Gau-8 gun. This value is not recorded by firing single shots, but when firing full-auto on the ground at a target during maintenance checks. The gun must meet or exceed that value to pass a maintenance check. It's quite likely better than that when new gun barrels are used, but we have no specific data on that. Simulating these two guns having the worst level of precision right before they fail specifications, 8 mil 80% and 5 mil 80%, would be good enough I suppose.

 

Wind affect on dispersion would require a huge difference in airflow influence between each projectile fired to instantly increase dispersion, right after leaving the cannon barrel, as we currently see. It's so unlikely as to be practically impossible.

 

Dispersion is influenced by

1. internal quality (symmetry and dimensional conformance to specification) of the gun bore

2. consistency of center of mass and shape between projectiles

3. rigidness of mounting to the airframe

and

4. barrel heat from extended bursts will cause a temporary increase in bore diameter which will result in increased dispersion size. It must be realized that this is not instant, takes a certain number of rounds before it begins to occur, and also returns to normal quickly with a return of the barrel to ambient temperature, which again happens quickly with aircraft guns because of high airflow and lower temperatures at altitude.

 

The effects of all of these factors on dispersion are fully reflected in the results of ground tests. There would be no difference between a ground firing and an air firing, other than pilot error or airframe movement, neither of which are effectively simulated by simplistically increasing gun dispersion. i.e. if it's a flight issue, this would be reflected by the aircraft shuddering or swaying when firing, not by increasing cannon dispersion. A human player could adjust for this by firing short bursts to achieve smaller dispersion, for example.

 

Aside from all of this, there is no reason or data to suggest that the M61 Vulcan or the GAU-8 Avenger should be so incredibly less precise than their Russian counterparts. So why then is it so in the game?

 

This is either a mistake or intentional. If it's intentional, what was the reasoning?

Edited October 1, 2017 by Aries144

[dimitrischal]

[Ramsay]

Wikipedia talks about an ideal situation where the gun is grounded with no wind, and without any recoil.

 

The 8 mil dispersion diameter does not come from fixed ground tests of the M39 gun, which has much tighter 3 mil dispersion pattern when fired from a test rig.

 

... and this for the gun it's self

 

'The Machine Gun Volume 5', Chapter 46 20mm M39 (T160) Revolver Gun, page 404

Accuracy .... The radial dispersion (standard deviation) shall not exceed 1.5 mils in a burst of 50 rounds when mounted on a structure having a rigidity of 250,000 pounds per inch deflection

 

Source: https://ia800207.us.archive.org/5/items/The_Machine_Gun_V5/The_Machine_Gun_V5.pdf

Note:

68% of rounds hit within 1 standard deviation (+/- 1.5 mils)

95% of rounds hit within 2 standard deviations (+/- 3 mils)

Edited November 23, 2017 by Ramsay
The 8 mil dispersion is it's width, actual deviation is +/- 4 mil from the aim point

[Sarge55]

So is this a really difficult issue to fix which requires a lot of developer time to re-code? I presume so since it's been an issue for some time.

[PeaceSells]

I have no knowledge of the DCS engine, but I believe that changing a gun's dispersion should be just a matter of swapping one number with another...

[Aries144]

I have no knowledge of the DCS engine, but I believe that changing a gun's dispersion should be just a matter of swapping one number with another...

 

ETA: Make a backup copy of the file before changing anything!

 

You can do it yourself. It takes about 30 seconds, but it invalidates your game for multiplayer of course.

 

Look here:

 

DCS World\Scripts\Database\Weapons\shell_table.lua

 

Search for the Gau8, m39, and m61. In those categories, the "Da0" value controls dispersion size. It appears to correspond with mil. 0.0008 would be 8 mil, 0.0005 would be 5 mil, etc.

Edited October 7, 2017 by Aries144

[Aries144]

Other useful information on terms:

 

http://ballistipedia.com/index.php?title=Describing_Precision#Radial_Standard_Deviation_.28RSD.29

[PeaceSells]

Thanks for the info Aries! My post was actually just a response to the post above it, so I wasn't actually intending to edit anything, but since it seems so simple I might try it!