soul_man posted 10-22-1999 01:38 AM            

Is there a way to calculate location of shells and convert it into actual gunsight locations. For example, if conv. is set to 200, I would like indicators to tell me where each bank would hit at, say, d8 for Buff hunting or chasing the guy who is far off. I figure in the above example at d8 they would be 4x as wide as they started, but how do you translate that into the gunsight? Also about shell drop at distance. These would all be known to our armorers

peril posted 10-22-1999 08:09 AM            

The random affect of tradectory should make them to spread to be of any use past d600.

If you also set convergance to say 300, at 600 they will be so spread as to have NO consistant pattern.

In otherwords, Nope.

Sidewinder posted 10-22-1999 11:56 PM            

Actually, convergence for wing mounted guns works like this. Assume the default of 300 is set. Also assume a perfect vacuum.

At d6, the bullet spread is back out to the original width of the wings. In other words, the bullets leave the guns, converge to a dot at d3 and then at d6 the bullet path is back to the position of the wing guns. At d9 the bullet pattern is twice the wing mount width.

Unfortunately reality has air resistance. at d6 in the real world the bullet has slowed and the pattern should actually be wider than the wing mounts by a small distance. Since we do have bullet drop and various other forces modeled, this is probably how it works in WB. In any case, the difference probably isn't worth arguing over.

What is probably most important is your guns are hitting at about the same distance apart at d1 and d5, d2 and d4, and d0 and d6 with d3 being the crossing point. if you can fly at a steady d1, you can probably shoot both wings off at once on a target drone. At d3 you would only hit the tail or other pin-point because of convergence.

soul_man posted 10-23-1999 01:29 AM            

Agree with the above. But how can I find out 1.) How far apart are my guns initially and 2.) What do the pixels on the gunsight mean? Even if I knew the angle formed I could calculate the rest. And what about drop of shells? That should be a known value (so many feet at so many yards), if that was known and the angle subtended by a certain inter-pixel difference then we could make functional sights instead of guesstimating.

Iago posted 10-23-1999 02:50 AM            

Soul, I think you're missing the point in some ways. Gunnery in WWII fighters was very much about 'guesstimating'.

You talk about knowing the value for bullet drop, etc., but you have to realize that even if those were known for every type of ordinance (and you'd have to have a great memory and a calculator brain to be doing those calculations (distance to target, closure rate, etc.) in mid-flight!), dispersion renders all those figures as ideal, and not realistic. Then there is the factor of how many G's you're pulling, the effect of different air-density (altitude) on bullet-drop (don't know if that's modeled, but what the heck), and so on. There are just too many different factors effecting the flight-path of a projectile, even before it leaves the barrel, for it to be an exact science.

BTW, have you been to Cuda'a Gunsight page? There are a lot of gunsights that make 'guesstimating' a lot easier...

jedi posted 10-23-1999 09:50 PM            

You can do some trial and error offline. Use the bomber intercept mission. Make yourself invincible. Hold yourself at d6, say, with your convergence at d6. Shoot until you're getting consistent strikes. Then, while holding down the trigger, take a screen shot. This will show you where your hits are on the gunsight.

Same principle will work for shots outside convergence.

Sidewinder posted 10-24-1999 04:48 PM            

Bullet drop is simple. 32 feet per second per second. Normal acceleration due to gravity.

To complicate matters, the bullet is set to converge at d3 or 300 yds. So the actual bullet path is slightly above this initially, passes through the convergence point and then drops below in a smooth arc. A classic example of the arc is the trajectory of artillery shells.

Now that you know this, take the muzzle velocity and travel time to figure roughly where the bullet actually is. To complicate matters, we aren't in a vacuum so the bullet speed begins slowwing as soon as it leaves the gun. Also, the trajectory of a high velocity bullet such as the .50 machine gun doesn't have a lot of bullet drop initially so the difference isn't that perceptible.

Ignoring all the fancy calculations, the bullet path will always be roughly the same every time so that you can shoot great distances (B25H 75mm kills B17 at D11 in offline tests) and still maintain a great deal of accuracy.

Gunnery gets complicated with both shooter and target moving. Remember that the bullet goes in a perfectly straight line for practical purposes (nose mounted P38 guns to simplify) and you have to lead the target so that the bullet and target arrive at the same point at the same time. This led to the lead computing gun sights in the late model P51s and others. What you see is what looks like huge bullet drop as you fire while turning. The bullet drops away with a very tight arc depending on the type some are worse. The LW camp complains loudly that they have to shoot at d2 now because the slower velocity LW 20mm guns need more lead time than other 20mm guns. Just one example of how many things were wrong in the sim.

flakbait posted 10-25-1999 04:24 AM         

Actually I prefer using the SWAG method. SWAG involves several dozen highly complex calculations as well as a few pre-requsite figures.

BTW, SWAG means Scientific Wild A$$ Guess

-ze--- posted 10-26-1999 10:08 PM         

I made off line tests with B25H and P39D to calibrate gunsight for 75mm and 37mm shells respectively.

Each trace below center means 500, 1000, 1500, 2000 yards.

Here goes the gunsights:

B25H1.gst

4

-2,-4,3,-4

-4,-8,5,-8

-2,-12,3,-12

-4,-17,5,-17

B25H3.gst

4

-4,-7,4,-7

-7,-13,8,-13

-4,-20,4,-20

-7,-27,8,-27

P39D1.gst

14

5,0,5,1

0,5,1,5

-5,0,-5,1

11,0,11,1

0,11,1,11

-11,0,-11,1

-2,-3,3,-3

-4,-6,5,-6

-2,-9,3,-9

-4,-13,5,-13

16,0,21,0

0,16,0,21

-16,0,-21,0

0,-16,0,-21

P39D3.gst

14

8,-1,8,1

-1,8,1,8

-8,-1,-8,1

17,-1,17,1

-1,17,1,17

-17,-1,-17,1

-4,-5,4,-5

-7,-10,8,-10

-4,-15,4,-15

-7,-20,8,-20

26,0,34,0

0,26,0,34

-26,0,-34,0

0,-26,0,-34

By the way, Ju87 gunsight are same as P39.