Air density and ballistics.

[Crious]

Hi,

Does air density based on height or/and temperature affects ballistics in the game?

Do bullets travel faster in high attitudes?

Do bullets travel slower in freezing conditions?

Do i have to have less lead when shooting on an opponent at 6000 meters than at sea level for the same tas and angular velocity?

Do i have to add more lead when i dogfight at conditions well below 0 degrees Celsius for the same tas and angular velocity?

Thanks in advance for any answers.

[Crious]

Some one ?

[[CPT]Crunch]

Yes, but not enough to worry about nor affect your typical marksman's shooting ability.  Your average gun will have greater mechanically induced variance in it than these.

[Dragon1-1]

Altitude should affect bullet trajectory a good deal more than that. For one, drag is inversely proportional to static pressure, and static pressure at 10km is roughly one quarter that at SL. So, drag would be four times lower, making the bullet trajectory significantly flatter. This is a far bigger effect than variances in propellant.

I don't think it's simulated, but it should affect all rounds quite a bit at high alts, especially smaller ones. Vertical convergence would effectively end up being altitude-dependent.

[[CPT]Crunch]

Yeah, but as a marksman you'll never notice it because your not stationary.  There's a reason they belted tracers.

[Dragon1-1]

Shooting at convergence distance, you'd very much notice that bullets that would have hit dead center of the gunsight at SL go over the target's wings at 30kft. Again, this is a rather large effect, if the bullets have 1/4th the drag they normally do, your vertical convergence would be out of whack at high altitudes. Also, small caliber bullets would retain more penetrating power at longer ranges, which could make a difference hosing down a bomber's engine nacelle with rifle caliber MGs. Yes, with wing guns the effect would be lost in the general dispersion, but the same is not true if you're trying to do long range gunnery with centerline armament.

[[CPT]Crunch]

So what, gravity is constant, the bullet is going to always drop at the same rate.  So adding a different batch or brand of powder from a contract which has slightly higher velocity or changing ammo type will do exactly the same thing at ground level, any experienced shooter instinctively adjusts and compensates.  Still a minor detail, if anything the higher velocity under lower drag conditions is a net benefit and should be seen as an overall advantage. 

 

If that sort of precision was a thing everyone would have gone the Russian route with one gun or two guns instead of loading down with banks of guns.

[Dragon1-1]

You don't get how drag works, do you? No, you can't get an effect equivalent to a 4x drag reduction with propellant variation. It's just not possible, because drag depends on speed. More speed, more drag. And no, changes in powder don't get you nearly the same changes, not by an order of magnitude.

 

Also, high school physics: gravity works the same, but the bullet flies faster. It will take the same time to get to convergence distance, but it will be much further away when it does. So, if your bullet stream crossed the sight line at 400m at sea level, now it will do so at over 1000m. So if you put your sight on the bandit 400m away and shoot, you'll miss high.

 

A marksman will definitely notice that. If you wouldn't, then you're not worthy of being called one. Yes, you may be able to compensate, but you'll notice you have to do that. Also, there's a small matter that IRL, you wanted to hit with the first burst, otherwise tracers would only announce to your target that you were attacking.

2 hours ago, [CPT]Crunch said:

If that sort of precision was a thing everyone would have gone the Russian route with one gun or two guns instead of loading down with banks of guns.

That sort of precision was a thing with anything that didn't have wing guns. P-38 was notorious for this because it had the guns in the nose, and sure enough, P-38 aces could hit targets with their MGs at ranges that other fighters had trouble hitting with cannons. Poor accuracy of wing guns was known at the time, while not an issue for pilots who didn't know how to shoot anyway (rows of guns were used so they could be set in a box pattern, and they were in the wings to avoid the need for synchronization), when gyro and eventually radar gunsights became a thing, every new design had guns as close to the centerline as they could make them fit. With all the guns harmonized towards a single point, this kind of precision is not hard to achieve.

 

IRL, at altitude, bullets fly faster and hit harder. While the effect is small, with a fixed gunsight and tightly grouped weaponry, you'd probably notice it.

Edited April 7 by Dragon1-1

[[CPT]Crunch]

Many of the aircraft, even in sim, had sights with the ability to adjustable mil's to compensate for weapons employment, yet you won't find a single instance in any manual with instructions for use as an aid in air gunnery, nor any pilot account of actual use for that purpose.

 

I didn't say any of that about drag, gravity will always drop your bullet at the same rate, the barrel, it's velocity, and ballistic coefficient of the bullet itself will determine overall performance.  If you level a gun and drop a bullet from bore height as you squeeze the trigger, both the fired bullet and the one dropped will hit the dirt at the exact same time.  Even if you fired it in a vacuum result's still the same.  The bullet is simply never going to achieve any real escape velocity in that short amount of time, even at such an extreme.

 

Next someone will demand the earths gravity to be modeled because it varies substantially and isn't uniform.  That too affects your gunnery.

 

[Dragon1-1]

1 hour ago, [CPT]Crunch said:

If you level a gun and drop a bullet from bore height as you squeeze the trigger, both the fired bullet and the one dropped will hit the dirt at the exact same time.  Even if you fired it in a vacuum result's still the same. 

It's not about time. It's about distance downrange. What you're doing is trying to tell me a bullet in vacuum would drop in the same spot as a bullet fired at sea level. My elementary understanding of physics suggest that is obviously not the case. Even if the gravity is the same, the bullet will have a shorter range in air, because drag slows it down. Duh.

 

Do you even know what vertical convergence is, and how it works? 

 

1 hour ago, [CPT]Crunch said:

the barrel, it's velocity, and ballistic coefficient of the bullet itself will determine overall performance. 

Look, you did, in fact, mention drag. Ballistic coefficient is important because it goes into the drag equation. It's basically a ratio of density times length to drag coefficient. It does not take air density out of the equation. In fact, you need to know air density to use it properly. This is usually encountered when dealing with artillery (altitude is a major factor there, for instance when fighting in the mountains, shells fly further), or when sniping, but it's true for any gun.

 

Snipers don't compensate for variations in Earth's gravity, but they do for weather conditions and altitude. What does that tell you about how those things are different?

1 hour ago, [CPT]Crunch said:

Many of the aircraft, even in sim, had sights with the ability to adjustable mil's to compensate for weapons employment, yet you won't find a single instance in any manual with instructions for use as an aid in air gunnery, nor any pilot account of actual use for that purpose.

Fighter aircraft rarely had those adjustable sights, most of the time you just looked at the gunsight markings. Besides, in WWII things were a lot more "seat of pants" than they are today. Ballistics varying with altitude were something that pilots would have to learn to instinctively compensate for. In practice, it's main effect would be to make aerial gunnery less predictable and less well behaved. Particularly with high aspect shots, at high altitude bullets would get to target faster, requiring you to pull less lead (of course, in actual WWII, high aspect shots simply missed most of the time).

Edited April 8 by Dragon1-1