Bug Report: F-15 gun accuracy does not match sources

[PeaceSells]

I believe the sight and the eagle's better high AoA control may have a little more to do with that, but that's just a feeling.

 

It's even easier to hit ground targets with the F-15 gun than the Su-27 gun, it can't be the AoA control or the sight... It's the considerably higher spread coupled with the considerably higher rate of fire...

[Aries144]

Can we please stay on topic?

[jackmckay]

• The F-5's and F-15's guns both use the 0.0022 value.
  
• The A-10's gun uses a value of 0.0017.
  
• The Mirage is 0.0008
  
• the Harrier's gunpod is 0.0005
  
• the Mig-29/Su-27 is 0.0005
  
• the Su-25 and Su-25T are 0.0005
  
• the Mig-21 is 0.0007
  
• the Ka-50 is 0.0005 for HE and 0.0004 for AP.
  

 

You can modify the values in the file yourself and see the change in-game, it just won't pass integrity check for multiplayer.

 

The file is called "shell_table.lua" and is located in Eagle Dynamics\DCS World\Scripts\Database\Weapons

 

Good to know data. As I already noted in one post that F15 gun behaves like buckshot barrel with birdshot shells. That gives F15 and F5 5x times better accuracy in gunzo dogfight which is fine as Su27 and other pilots will develop better skills in gun aiming practice making F15 and F5 pilots 5x times worst gunners. Thats why ED had to make this little tweak to help them out ofc.

 

Forgive me for not reading all posts after page 2 but may I add to this topic that other guns besides F15/F5 seems to have lower range as rounds seems to rapidly slow down somehow (clean Su27 chasing droptanked F15 firing from below upwards on the edge of gun range means that not single round will hit target).

[Aries144]

For example 8 mil 80% is an 8 foot diameter at 1,000 feet but at 2,000 feet it’s not a 16 ft diameter 80% circle, it’s larger.

 

That's not accurate. Dispersion IS linear. At 2000 ft 8 mil would be a 16ft diameter circle.

 

The 80% isn't being correctly understood either.

 

As guns wear, eventually they lose precision all the way down to a point where they won't stabilize projectile anymore and the projectiles begin to tumble in flight, becoming wildly inaccurate and losing velocity quickly. 8 mil, 80% is a maintenance standard for when a gun is worn out and needs repair/parts replacement. If more than 20% of fired shots fall outside an 8 mil circle, it's time to replace parts in the gun.

 

That's all the 80% part means. A new M61A1 doesn't shoot 8 mil, 80%. The new gun we see in our video evidence certainly performed much better. As shown in the video, the M61 actually shoots a main group smaller than 8 mil with a very low percentage of outlier rounds (1-5%) falling outside of 8 mil.

 

DCS doesn't simulate aged hardware, it takes everything as if it is brand new from the factory, so we should probably throw the 80% out completely. It simplifies things greatly, as we'd need to get into Circular Error probable to accurately calculate how far outside of 8 mil the 20% of shots would land. Besides, I don't think DCS can model an 80% CEP. I think it is hard coded to always do a 50% CEP, with the Da0 value indicating what the maximum extreme spread is allowed to be, which means that with a value of 8 mil, 50% of shots are falling into a dispersion of about 4 mil, with the rest spreading out everywhere between 4 and 8 mil.

 

Guys, please go back and have a look at the first post. It's been updated.

Edited December 20, 2017 by Aries144

[Aries144]

Forgive me for not reading all posts after page 2 but may I add to this topic that other guns besides F15/F5 seems to have lower range as rounds seems to rapidly slow down somehow (clean Su27 chasing droptanked F15 firing from below upwards on the edge of gun range means that not single round will hit target).

 

In real life, this would be a function of Muzzle Velocity and Ballistic Coefficient. I'm not sure how accurate DCS' ballistics modeling is and I'm afraid it's outside the scope of the current discussion.

[jackmckay]

Well could be, but comparing to GSH-301 which has 900m/s MzlVel, M61A1 has 1,050m/s. Fire rate is 6000/6600 for Vulcan and 1500 for Gryazev-Shipunov which is logical as Vulcan has 6 barrels to easily cool down. What interest me most is accuracy. In DCS I found out that it's way easier to score a gun kill in F15/F5 (even F5 doesn't have M61 but 2xM39 which are similar to GSh301) than in Su27 or any other fighter. Dispersion rate is logical explanation, but is that real or tuned up and if, why? I mean booth rounds travel between mach 2.5 to mach 3 and GSh still can't hit precisely (even inflict any damage) aimed at F15 tail in chase at around 500m advantage. That's kind of stinky to me now, not because I push some "balance" but for pure realism in this aspect of dogfight between two rivals. Thanks for expanding this segment.

[PeaceSells]

^^ as a matter of fact, the point of this thread is to develop a way to test and solve the exact object of your complaint...

[Aries144]

Updated the first post with links to some Shadowplay recordings. I believe this clearly demonstrates that the numbers in the lua do, in fact, directly relate to mil. 0.0008 is 8 mil, 0.0022 is 22 mil, 0.004 is 40 mil, etc.

 

The Da0 value indicates extreme spread. A 50% CEP, based on the Da0 divided by 2, seems to be evident. For a Da0 value of 0.004 (40 mil), approximately 50% of rounds will fall into a 20 mil diameter while the remaining 50% fall between 20 mil and 40 mil. Only a small percentage of rounds fall at the extreme edge of the extreme spread (40 mil).

Edited December 22, 2017 by Aries144

[Aries144]

New information incoming. I just discovered that it is possible to freeze the aircraft using active pause, decelerate time using alt z, and shoot the cannon in slow motion with no movement of the aircraft. This will make the next videos posted as accurate as if the aircraft were stationary on the ground!

[SinusoidDelta]

New information incoming. I just discovered that it is possible to freeze the aircraft using active pause, decelerate time using alt z, and shoot the cannon in slow motion with no movement of the aircraft. This will make the next videos posted as accurate as if the aircraft were stationary on the ground!

 

Yep, I mentioned that earlier in this post but couldn’t remember the key binding :thumbup:

[Aries144]

Yep, sorry. Must have missed that. Been bouncing back and forth between this and other personal things. Not enough time in the day!