Bug with machine gun bullet ballistics

[Herra Tohtori]

Hello!

 

Some time ago, when I was just getting used to the P-51D by flying some of the gunnery training missions, I encountered a strange bug. The mission I was flying was the simple aerial gunnery training mission with two P-51D drones flying in a very predictable pattern. Initially, everything worked fine, although my aircraft actually had some difficulty catching up to the other aircraft (most likely because I'm not really familiar with the tolerances of the engine and I was experiencing some strange engine seizures, so I tried to keep my engine at lower than normal RPM's and boost pressures).

 

In the middle of the mission, however, I noticed something weird. My bullets stopped catching the enemy fighter, even though I was well within a reasonable range. I had to get right up to their tail to inflict any damage or even hit them - the bullets would just not go far enough.

 

External camera confirmed that the bullets had extremely short range when this issue happened - in fact when I further experimented, I ended up flying through ricochets from the ground.

 

At first I thought it was an issue with my gunnery.

 

Then I thought it was something making muzzle velocity too slow and thought it might be that bullets didn't inherit plane's speed properly - but then I did some mental math - my fighter was going slower than 360 km/h, which means less than 100 m/s. The muzzle velocity of AN/M2 machine guns is cited as 860 m/s, which means that at most my aircraft's velocity was roughly 1/10th of the muzzle velocity. Whether the muzzle velocity relative to aircraft was 860 m/s or 760 m/s, the bullets should still keep going much, much further than they actually did. So clearly, problem with object speed inheritance wasn't sufficient to explain the issue.

 

Since this behaviour seemed interesting, I made a video of it, accessible here:

 

 

Unfortunately, I have no real tools to determine what the initial muzzle velocity of the projectiles was when the bug occurred; I guess it would be possible to interpolate that from the video. It's possible that muzzle velocity was affected by the bug, or it wasn't - it was hard to tell.

 

The more interesting part of the video is the improbably high drag coefficient of the projectiles - they seem to slow down so fast that before the tracers go out my aircraft starts to catch them. Ricochets, being slowed down by the impact, actually end up going past my aircraft as I fly through them.

 

 

I haven't reproduced the behaviour yet (I've been busy with other stuff, both RL and other games) so I don't know if this is a consistent bug, sporadic bug, heisenbug or a fixedbug. I hadn't made a forum account yet at the time I encountered the bug, so it's entirely possible that it has disappeared after some update.

 

If needed I'll try to reproduce the issue and provide further information (logging, tracks, video).

 

Has anyone else ever seen this behaviour?

 

My system is Win7 64bit, i5-2500K, 8GB RAM, GTX660Ti 2GB VRAM, for performance reference (game runs quite well).

[Der_Fred]

It is possible for a bullet to come straight back at you.. depending on what it, and how it, hits an object.

 

There's a video of a guy firing either a .303 or .5 inch single shot at a rock about 100m away... the ricochet clipped his right ear muff - he was very lucky indeed.

 

If your scenario happened with one or two shell.. I'd think it is possible... but if it happens all the time, then there could be a bug.

[Flagrum]

It is possible for a bullet to come straight back at you.. depending on what it, and how it, hits an object.

 

There's a video of a guy firing either a .303 or .5 inch single shot at a rock about 100m away... the ricochet clipped his right ear muff - he was very lucky indeed.

 

If your scenario happened with one or two shell.. I'd think it is possible... but if it happens all the time, then there could be a bug.

What he describes is a different effect - as far as I understood it. His bullets ricochet in an angle away from him (the usual case we all know). But they are then so much slowed down that he catches up with his plane and even flies through them.

[Irregular programming]

Yeah, the bullets seem to think they are being fired from a stationary position.

Edited March 19, 2014 by Irregular programming

[ZaltysZ]

What does tacview show? It might be just a graphical bug.

[Yo-Yo]

Hello!

 

Some time ago, when I was just getting used to the P-51D by flying some of the gunnery training missions, I encountered a strange bug. The mission I was flying was the simple aerial gunnery training mission with two P-51D drones flying in a very predictable pattern. Initially, everything worked fine, although my aircraft actually had some difficulty catching up to the other aircraft (most likely because I'm not really familiar with the tolerances of the engine and I was experiencing some strange engine seizures, so I tried to keep my engine at lower than normal RPM's and boost pressures).

 

In the middle of the mission, however, I noticed something weird. My bullets stopped catching the enemy fighter, even though I was well within a reasonable range. I had to get right up to their tail to inflict any damage or even hit them - the bullets would just not go far enough.

 

External camera confirmed that the bullets had extremely short range when this issue happened - in fact when I further experimented, I ended up flying through ricochets from the ground.

 

At first I thought it was an issue with my gunnery.

 

Then I thought it was something making muzzle velocity too slow and thought it might be that bullets didn't inherit plane's speed properly - but then I did some mental math - my fighter was going slower than 360 km/h, which means less than 100 m/s. The muzzle velocity of AN/M2 machine guns is cited as 860 m/s, which means that at most my aircraft's velocity was roughly 1/10th of the muzzle velocity. Whether the muzzle velocity relative to aircraft was 860 m/s or 760 m/s, the bullets should still keep going much, much further than they actually did. So clearly, problem with object speed inheritance wasn't sufficient to explain the issue.

 

Since this behaviour seemed interesting, I made a video of it, accessible here:

 

 

Unfortunately, I have no real tools to determine what the initial muzzle velocity of the projectiles was when the bug occurred; I guess it would be possible to interpolate that from the video. It's possible that muzzle velocity was affected by the bug, or it wasn't - it was hard to tell.

 

The more interesting part of the video is the improbably high drag coefficient of the projectiles - they seem to slow down so fast that before the tracers go out my aircraft starts to catch them. Ricochets, being slowed down by the impact, actually end up going past my aircraft as I fly through them.

 

 

I haven't reproduced the behaviour yet (I've been busy with other stuff, both RL and other games) so I don't know if this is a consistent bug, sporadic bug, heisenbug or a fixedbug. I hadn't made a forum account yet at the time I encountered the bug, so it's entirely possible that it has disappeared after some update.

 

If needed I'll try to reproduce the issue and provide further information (logging, tracks, video).

 

Has anyone else ever seen this behaviour?

 

My system is Win7 64bit, i5-2500K, 8GB RAM, GTX660Ti 2GB VRAM, for performance reference (game runs quite well).

 

The right answer is: do not overheat M2 :)

[NineLine]

The right answer is: do not overheat M2 :)

 

Is there a recommended burst amount not to overheat the guns, I didnt see anything in the DCS Manual or even the actual manual, although I will admit I just skimmed through :)