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PlaneEater
05-26-2004, 12:43 AM
I posted this in the PF forum, but since not everybody reads that, I thought I'd repost this here.

I wanted to boil down the Browning dispersion discussion to a single, clear post, so Oleg and everybody else don't have to wade through a 30 page topic to finally gather all the information that's been posted. People are welcome to add to this ONLY if you are posting data, scans or information from manuals, texts, handbooks, or other credible sources.

When I sat down and thought about this whole issue for a while yesterday, and looked again at the bench test screenshots Gibb did, a few things occured to me.

First, I think part of the problem stems from IL-2's dispersion system--it uses a simple randomized X,Y offset that moves the impact point around inside a preset-size box.

Here's the problem that crops up with that--it's too random. (Here's the "when will I ever use this?" moment from my high-school statistics class)

When you simply give every shot a random X,Y point offset within a preset distance from the center point, Bullet X has just as much probability of hitting the very corner as it does landing dead-center.

That's the polar opposite of how gunfire--ANY gunfire--actually disperses. It follows a bell curve dispersion. You've probably seen one of these before:

http://www.susd.org/district/currinstruction/images/normal-curve.gif

With IL-2, any given bullet could land anywhere within the pre-designated 'accuracy grid'. In real life, 55% of the shots will land within 1/6th of the maximum possible dispersion distance from dead center; 79% would land within 1/4th.

With a weapon that has a wider dispersion, the way the Browning does right now, that inaccuracy is doubly exaggerated, because a bullet is much more likely than in reality to veer way off of dead-center.

Blutarski posted this down in the depths of a different thread:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
According to a 1950 USAF fighter gunnery manual in my library, the M2 50cal in a rigid a/c mounting (wing or nose) firing in the air-to-air mode is credited with a 100 pct dispersion zone of 8 mils. In 1950 USAF parlance a mil is the apex angle formed by an isosceles triangle with sides 1000 ft long and a base of 1 foot. Stated in another way, 100 pct of shots fired by a single 50cal will strike within a circular area 8 feet in diameter at a range of 1000 feet (333 yards). At 500 meters (547 yards), the diameter of the circular area would be about 13 feet.

According to the standard exterior ballistics law of distribution, at 500 meters the distribution of hits within that circle will be as follows:

50 pct of hits strike within a circle of 2 mils (3.25 ft) diameter.

82 pct of hits will strike within a circle of 4 mils diameter (6.5 feet) diameter.

96 pct of hits will strike within a circle of 6 mils diameter (9.75 feet).

With a point convergence set at 547 yards / 500 meters (a very long range indeed for air to air), a battery of six 50cals firing a one second burst at that range would theoretically put 36 bullets out of 72 bullets fired into a area of 8.3 square feet (less than one square yard), i.e. - about 4 bullets per square foot.

Since hitting density varies inversely according to the square of the range, it can be seen that the same six guns firing at 250 meters point convergence would be quite deadly, depositing those same 36 hits within a circular area of 2 square feet, i.e. - about 18 bullets per square foot.

Please note that this is dispersion of air to air fire expected by the USAF, and was not ground based bench test results.

If you were watching a strafing run, with bullets striking the ground, over eighty percent of the bullets would be striking within the middle 50 percent of the bullet pattern width.
<HR></BLOCKQUOTE>

Considering how crucial the gunnery model is to the sim, I really, REALLY hope this is something that gets looked at. I'm no master programmer, but I DO have enough experience with object oriented C++ to know that while altering the gunnery model might be complicated, it won't require re-writing the game from the ground up or anything else that drastic. Considering how simplified the current bullet disperion code is with the simple X,Y grid offset, instead of an angle theta, I'm surprised it wasn't re-done a while ago.

Chochacho isolated the flaw and has a solid solution.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
If only the dispersion was cone-shaped. The bullets spread out in a square pyramid shape.

The dispersal model currently uses random X and Y offsets.

To be correct it should use a random angle theta and a dispersal r where r follows the shape of half a bell curve.
<HR></BLOCKQUOTE>

Here's what that would change: when a bullet is fired, instead of retrieving the entered maximum dispersion distance and generating a random X and Y coordinate within that distance, it would generate a random dispersion direction (like a random heading on a compass with the face of the compass held to end of the gun's barrel), and then use a random bell-curved value to see how far in that direction the angle of the bullet's path should disperse (relative to dead center).


Second, and you probably have seen this argument before, something is numerically wrong with the Browning .50. It was probably MEANT to be right, but something either got misread or mis-entered. Here's why:

http://mitglied.lycos.de/jaytdee/fbg/b2392.jpg

This is the Browning .50's impact profile, at 300 meters, with a single shot from each gun (nose guns on the B239; P-39's dispersion pattern is essentially identical). Recoil from sustained fire is not a factor here.

http://mitglied.lycos.de/jaytdee/fbg/Ki84Ia1.jpg

This is the Ki-84Ia's Ho-103 nose guns from the same position, with the same single-shot burst.

The Ho-103 is a COPY of the Browning .50, and a mechanically inferior one as well. It fires a shortened 12.7x88mm round, giving it less energy and a faster drop. The breech assembly and the gun as a whole is built to looser tolerances, degrading accuracy, and is lighter weight than the Browning. With less mass, the gun's mass does not 'absorb' the shock and per-round recoil as well. The barrel is shorter, which means less muzzle velocity and less stabilization of the projectile--both of which are major detriments to accuracy, especially the shorter barrel length.

Either the Ho-103 is incorrect, or the M2 Browning .50 is. One of them MUST be changed.


Here's something else. Compare the Browning .50...

http://mitglied.lycos.de/jaytdee/fbg/b2392.jpg

--and the previously fault-proven Ho-103--

http://mitglied.lycos.de/jaytdee/fbg/Ki84Ia1.jpg

--with the other .50 caliber cowl and nose mounted weapons in the game: the MG131--

http://mitglied.lycos.de/jaytdee/fbg/Bf109G61.jpg

--and the UBs:
http://mitglied.lycos.de/jaytdee/fbg/Yak1b1.jpg

Regardless of whether the Ho-103 has problems, there is an obvious similarity between the MG131, UBs and Ho-103. That similarity, puzzlingly, does not extend to the Browning.

Basically, a very large portion of the community just wants somebody to double-check the numbers that are currently punched in for the .50 cal weapons. Maybe something got entered wrong, like the single extra-fast-firing wing gun on the P-47 in ver 1.0 of FB.

If this disparity is intentional, we just want to see the sources that were used to create the .50s in FB so we can understand why. A number of community members have found WWII documents dealing with the M2 that contradict its behavior in FB, and we want to get to the bottom of the differences.

One last thing I wanted to add--I've been flying the razorback P-47s and the P-51D a lot recently. What I'm starting to think is that with the 2.01 patch changes to damage modeling, the Browning .50 may be too strong.

I have this nagging suspicion that with a corrected dispersion and 2.0 damage, they'd be perfect.

PlaneEater
05-26-2004, 12:43 AM
I posted this in the PF forum, but since not everybody reads that, I thought I'd repost this here.

I wanted to boil down the Browning dispersion discussion to a single, clear post, so Oleg and everybody else don't have to wade through a 30 page topic to finally gather all the information that's been posted. People are welcome to add to this ONLY if you are posting data, scans or information from manuals, texts, handbooks, or other credible sources.

When I sat down and thought about this whole issue for a while yesterday, and looked again at the bench test screenshots Gibb did, a few things occured to me.

First, I think part of the problem stems from IL-2's dispersion system--it uses a simple randomized X,Y offset that moves the impact point around inside a preset-size box.

Here's the problem that crops up with that--it's too random. (Here's the "when will I ever use this?" moment from my high-school statistics class)

When you simply give every shot a random X,Y point offset within a preset distance from the center point, Bullet X has just as much probability of hitting the very corner as it does landing dead-center.

That's the polar opposite of how gunfire--ANY gunfire--actually disperses. It follows a bell curve dispersion. You've probably seen one of these before:

http://www.susd.org/district/currinstruction/images/normal-curve.gif

With IL-2, any given bullet could land anywhere within the pre-designated 'accuracy grid'. In real life, 55% of the shots will land within 1/6th of the maximum possible dispersion distance from dead center; 79% would land within 1/4th.

With a weapon that has a wider dispersion, the way the Browning does right now, that inaccuracy is doubly exaggerated, because a bullet is much more likely than in reality to veer way off of dead-center.

Blutarski posted this down in the depths of a different thread:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
According to a 1950 USAF fighter gunnery manual in my library, the M2 50cal in a rigid a/c mounting (wing or nose) firing in the air-to-air mode is credited with a 100 pct dispersion zone of 8 mils. In 1950 USAF parlance a mil is the apex angle formed by an isosceles triangle with sides 1000 ft long and a base of 1 foot. Stated in another way, 100 pct of shots fired by a single 50cal will strike within a circular area 8 feet in diameter at a range of 1000 feet (333 yards). At 500 meters (547 yards), the diameter of the circular area would be about 13 feet.

According to the standard exterior ballistics law of distribution, at 500 meters the distribution of hits within that circle will be as follows:

50 pct of hits strike within a circle of 2 mils (3.25 ft) diameter.

82 pct of hits will strike within a circle of 4 mils diameter (6.5 feet) diameter.

96 pct of hits will strike within a circle of 6 mils diameter (9.75 feet).

With a point convergence set at 547 yards / 500 meters (a very long range indeed for air to air), a battery of six 50cals firing a one second burst at that range would theoretically put 36 bullets out of 72 bullets fired into a area of 8.3 square feet (less than one square yard), i.e. - about 4 bullets per square foot.

Since hitting density varies inversely according to the square of the range, it can be seen that the same six guns firing at 250 meters point convergence would be quite deadly, depositing those same 36 hits within a circular area of 2 square feet, i.e. - about 18 bullets per square foot.

Please note that this is dispersion of air to air fire expected by the USAF, and was not ground based bench test results.

If you were watching a strafing run, with bullets striking the ground, over eighty percent of the bullets would be striking within the middle 50 percent of the bullet pattern width.
<HR></BLOCKQUOTE>

Considering how crucial the gunnery model is to the sim, I really, REALLY hope this is something that gets looked at. I'm no master programmer, but I DO have enough experience with object oriented C++ to know that while altering the gunnery model might be complicated, it won't require re-writing the game from the ground up or anything else that drastic. Considering how simplified the current bullet disperion code is with the simple X,Y grid offset, instead of an angle theta, I'm surprised it wasn't re-done a while ago.

Chochacho isolated the flaw and has a solid solution.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
If only the dispersion was cone-shaped. The bullets spread out in a square pyramid shape.

The dispersal model currently uses random X and Y offsets.

To be correct it should use a random angle theta and a dispersal r where r follows the shape of half a bell curve.
<HR></BLOCKQUOTE>

Here's what that would change: when a bullet is fired, instead of retrieving the entered maximum dispersion distance and generating a random X and Y coordinate within that distance, it would generate a random dispersion direction (like a random heading on a compass with the face of the compass held to end of the gun's barrel), and then use a random bell-curved value to see how far in that direction the angle of the bullet's path should disperse (relative to dead center).


Second, and you probably have seen this argument before, something is numerically wrong with the Browning .50. It was probably MEANT to be right, but something either got misread or mis-entered. Here's why:

http://mitglied.lycos.de/jaytdee/fbg/b2392.jpg

This is the Browning .50's impact profile, at 300 meters, with a single shot from each gun (nose guns on the B239; P-39's dispersion pattern is essentially identical). Recoil from sustained fire is not a factor here.

http://mitglied.lycos.de/jaytdee/fbg/Ki84Ia1.jpg

This is the Ki-84Ia's Ho-103 nose guns from the same position, with the same single-shot burst.

The Ho-103 is a COPY of the Browning .50, and a mechanically inferior one as well. It fires a shortened 12.7x88mm round, giving it less energy and a faster drop. The breech assembly and the gun as a whole is built to looser tolerances, degrading accuracy, and is lighter weight than the Browning. With less mass, the gun's mass does not 'absorb' the shock and per-round recoil as well. The barrel is shorter, which means less muzzle velocity and less stabilization of the projectile--both of which are major detriments to accuracy, especially the shorter barrel length.

Either the Ho-103 is incorrect, or the M2 Browning .50 is. One of them MUST be changed.


Here's something else. Compare the Browning .50...

http://mitglied.lycos.de/jaytdee/fbg/b2392.jpg

--and the previously fault-proven Ho-103--

http://mitglied.lycos.de/jaytdee/fbg/Ki84Ia1.jpg

--with the other .50 caliber cowl and nose mounted weapons in the game: the MG131--

http://mitglied.lycos.de/jaytdee/fbg/Bf109G61.jpg

--and the UBs:
http://mitglied.lycos.de/jaytdee/fbg/Yak1b1.jpg

Regardless of whether the Ho-103 has problems, there is an obvious similarity between the MG131, UBs and Ho-103. That similarity, puzzlingly, does not extend to the Browning.

Basically, a very large portion of the community just wants somebody to double-check the numbers that are currently punched in for the .50 cal weapons. Maybe something got entered wrong, like the single extra-fast-firing wing gun on the P-47 in ver 1.0 of FB.

If this disparity is intentional, we just want to see the sources that were used to create the .50s in FB so we can understand why. A number of community members have found WWII documents dealing with the M2 that contradict its behavior in FB, and we want to get to the bottom of the differences.

One last thing I wanted to add--I've been flying the razorback P-47s and the P-51D a lot recently. What I'm starting to think is that with the 2.01 patch changes to damage modeling, the Browning .50 may be too strong.

I have this nagging suspicion that with a corrected dispersion and 2.0 damage, they'd be perfect.

Aaron_GT
05-26-2004, 04:28 AM
One sigma's about equivalent to the 82% figure, so the XM312 figures I looked at a while back for 1.5 mils for one sigma. For the M2 it seems to be around twice as much dispersion (in an aircraft mount?) as compared to the XM312 on a tripod.

PlaneEater
05-26-2004, 09:39 AM
Well, Oleg was perusing the boards at the same time I posted this, and he posted to another thread before and after I posted this, so I know he saw it.

I guess I've been ignored.

I'm not sure if that's Oleg's answer about the subject, but I hope it's not.

ZG77_Nagual
05-26-2004, 10:12 AM
Did you email him directly? il2beta@1c.ru

Your info is good but he has stated recently that only well-documented stuff sent directly to the beta address above will be looked at - too busy for the boards these days. Planeater - do go ahead and send this off to him - it may help. Once you've sent it we know all that can be done has.

[This message was edited by ZG77_Nagual on Wed May 26 2004 at 09:28 AM.]

Hoarmurath
05-26-2004, 11:13 AM
if you follow this link

http://www.movieflix.com/genre_list.mfx?genre=Documentary&sort=title&l=≤=&start=61

you will find a movie named "thunderbolt" made in 1944... In this movie, you'll see a lot of guncam footage of P47 straffing... To me it looked a lot like what we have in FB... Do you have other straffing guncam footage showing the "pinpoint spreading" you are fighting for please? i would like to compare.

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

LuftLuver
05-26-2004, 11:18 AM
Outstanding post PlaneEater.

On behalf of the community I thank you for your efforts and the time you spent on this to get the various data/posts to a clear and concise presentation. I don't think this will be ignored. The whole US Air Force will have to rely on these weapons in Pacific Fighters so it is in Oleg/1C's very best interest to get the .50cal right.

Not overdone, not a buzzsaw, not a flamethrower, not a one-shot wonder....just get them right.

""""""""""""""""""""""""""""""""""""""""""""
"All your bases are belong to us."

crazyivan1970
05-26-2004, 11:23 AM
That`s how those types of discussions should be conducted. Well done.

V!
Regards,

http://blitzpigs.com/forum/images/smiles/smokin.gif

VFC*Crazyivan aka VFC*HOST

http://www.rmutt.netfirms.com/coop-ivan.jpg

http://www.rmutt.netfirms.com/vfc/home.htm

Kozhedub: In combat potential, the Yak-3, La-7 and La-9 fighters were indisputably superior to the Bf-109s and Fw-190s. But, as they say, no matter how good the violin may be, much depends on the violinist. I always felt respect for an enemy pilot whose plane I failed to down.

ZG77_Nagual
05-26-2004, 11:28 AM
Hoarmuruth - respectfully I suggest you check planeater's post again. He's talking about statistical modeling not "pinpoint spreading" (which I notice you put quotes around?) - the error is most evident in nose mounted guns. Guncam footage does show how well FB models this sort of thing - and it does very well - Planeater has found a model to explain what appears to be an error noticed with the m2 relative to the other guns in the simm - and has come up with a way to correct it. Moreover he's done it in a clear, friendly and scientifically detached tone with no emotional valence that I can detect.

Hoarmurath
05-26-2004, 11:55 AM
Nagual, i respectfully suggest you take a closer look at actual guncam footage, as it seem there is a big difference between the theory and the application.

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

Gibbage1
05-26-2004, 12:00 PM
Remember that the P-47 had wing mounted guns. So unless your in the point of convergance, it will look rather dispersed. If you watch guncam footage of a P-38 with nose mounted MG's you will notice a HUGE differance in dispersion because its boarsighted.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Hoarmurath:
if you follow this link

http://www.movieflix.com/genre_list.mfx?genre=Documentary&sort=title&l=≤=&start=61

you will find a movie named "thunderbolt" made in 1944... In this movie, you'll see a lot of guncam footage of P47 straffing... To me it looked a lot like what we have in FB... Do you have other straffing guncam footage showing the "pinpoint spreading" you are fighting for please? i would like to compare.

http://hoarmurath.free.fr/<HR></BLOCKQUOTE>

"Most P-39's were sent to the Russians - so I guess that was an American secret weapon against our Russian allies."

Stan Wood, P-38 pilot who also flew the P-39.

ZG77_Nagual
05-26-2004, 12:02 PM
A couple variables (just for the sake of argument -I just think Planeater's view is well thought out enough that Oleg should see it)
First - the 47 guns are wing mounted - much more shake there - and there are 8(!). Next we don't know the convergence. And last - it was very common to kick the rudder a bit during straffing runs. Also there's a bit somewhere about how the wing guns were harmonized - to actually create wider dispersion - I think it was a diff in convergence settings for different sets of guns (inside, outside etc.) I'm not saying your wrong or planeater is right or that I even see any conflict in your perspectives. I just wanted to encourage Planeater to email Oleg with his interesting observations http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

Hoarmurath
05-26-2004, 12:15 PM
Well gibbage, the spreading of .50 was said to be wrong not only in P38, but also in other planes using those MGs. To be honest, i find the P38 fire to be fairly strong, lately i was able to straffe 15 grounded planes with a single load of ammo. All my straffing runs showed neat path of bullets, no more than a few meters wide even from a distance (i sometime keep pulling the trigger while pulling up)... I'm a long fan of wartime documentaries, and i saw no big discrepancies between what i see in game, and what i saw in some of these documentaries showing P38 in action.

I'll try to find such documentaries, like the one on the P47 on the web, but anyway, if you take a look at the "Thunderbolt" movie, you'll see that the area covered by the .50 bullets is at best 3 to 4 meters wide at convergence, with some spreading of the volleys in the vertical as well (not much, but some)... The main advantage of the P38 should be to obtain the same result at almost any distance, and not only at the convergence one... To be honest, the straight streams of bullets on targets i have seen in the "Black sheep" TV series, but never in documentaries.

So if the spreading of .50 is right for wing mounted MG, it must not be so far away from RL for nose mounted M2s...

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

Tater-SW-
05-26-2004, 01:29 PM
USAAF conversions were not consistant (unlike the navy which shared planes as a matter of routine and set them to harmonize at 1000ft). In fact, many wong mounted 50s were set to different ranges for different pairs of guns 250, 300 and 350 yards being one I've seen published for 6 gun planes like the P-51. This would really spread the rounds out.

Assuming you're right, hoarmurath, a simple question to ask is: are the dispersion patterns for similar weapons on non-US aircraft different? The answer from planeeater's screenshots is yes, even for very similar weapons. Something is broken on the M2, or all the others---or do you think only 1 MG type should be subject to what you think is correct divergence?

tater

BigKahuna_GS
05-26-2004, 02:13 PM
S!

__________________________________________________ _______________________
Tater-SW-

posted 26-05-04 12:29
USAAF conversions were not consistant (unlike the navy which shared planes as a matter of routine and set them to harmonize at 1000ft). In fact, many wong mounted 50s were set to different ranges for different pairs of guns 250, 300 and 350 yards being one I've seen published for 6 gun planes like the P-51. This would really spread the rounds out.
__________________________________________________ ______________________


If you ever read pilot accounts they hated setting different conversion settings to pairs of .50cals---that was only for inexperinced pilots to give them a chance to hit the target.

Veteran pilots wanted maximum destructive firepower from all guns set at the same convergence. Bud Anderson and Bob Goebel told me this in person.


___

CCJ: What do you define as the most important things a fighter pilot must know to be successful, relating to air combat maneuvering?

Robert S. Johnson :
It's pretty simple, really. Know the absolute limits of your plane's capabilities.
Know its strengths and weaknesses. Know the strengths and weaknesses of you enemy's fighters. Never fight the way your enemy fights best. Always fight the way you fight best. Never be predictable.

In "Fighter Aces," aviation historians Raymond Tolliver
and Trevor Constable compared Johnson's record with that of two German aces.
Werner Molders was the first ace to score 100 aerial victories and Erich Hartmann is the top scoring ace of all time with 352.

The authors noted that
Johnson "emerges impressively from this comparison." He downed 28 planes in 91 sorties, while Molders took 142 sorties to do the same, and Hartmann, 194.
________



http://www.warplaneswarehouse.com/planes_lg/MS1AOO_LG.jpg

"Angels of Okinawa"

PlaneEater
05-26-2004, 03:01 PM
About nose versus wing mounted guns:

Oleg has stated previously that the sim uses a single global model for each weapon type in different installations, and that the position itself--nose mount, wing mount, hand-swung, pintle mount, turreted--is then set up to further affect it.

So, while the same weapon data is being used in different positions, apparently the behavior of each position is also modeled with things like vibration and wing flex. I don't know how extensively, but it is.

Just to clarify that the characteristics of the weapon itself are seperated in the sim from where it's mounted--with the exception of prop-synchronized guns.

Blutarski2004
05-26-2004, 03:18 PM
The USAF Fighter Gunnery manual I have uses the same dispersion standard for harmonization of both nose and wing mounted 50cals.

BLUTARSKI

[This message was edited by crazyivan1970 on Wed May 26 2004 at 08:20 PM.]

Gibbage1
05-26-2004, 03:21 PM
Compairing the individual guns dispersion, yes. But there are many factors at play. A P-47 strafing the ground with its wing guns out of convergance cant be compaired to that of nose mounted guns because there is less shake and no convergance.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Blutarski2004:
The USAF Fighter Gunnery manual I have uses the same dispersion standard for harmonization of both nose and wing mounted 50cals.

BLUTARSKI

<HR></BLOCKQUOTE>

"Most P-39's were sent to the Russians - so I guess that was an American secret weapon against our Russian allies."

Stan Wood, P-38 pilot who also flew the P-39.

[This message was edited by crazyivan1970 on Wed May 26 2004 at 08:21 PM.]

PlaneEater
05-26-2004, 03:23 PM
Blutarski, any chance you can scan and post that? I have a few spots I can host images if you need it.

Hoarmurath
05-26-2004, 03:35 PM
Well, first point is... i didn't say anything insulting to anybody here, so gibbage, please, stay polite....

For the comparison between the M2s wing mounted and the spreading of other wing mounted HMGs, well, what plane are you comparing to? focke wulf 190 and messerschmitt 109 use HMGs exclusively nose mounted. Russian planes don't use wing mounted HMGs either.

For the comparison of the M2s nose mounted, all other planes having at least 2 HMGs nose mounted have them firing at reduced ROF through the propeller. And they only have 2 where the P38 have four, twice as much. It seem difficult to compare the amount of shaking with so different weapon placement.

The only twin engines having heavy nose armament is the Bf110, and it don't use HMGs, only rifle caliber MGs or cannons.

It seem to me that you try to compare machine guns mounting that are very different.

Anyway, i don't see how your spreading issue affect adversely the efficiency of the M2 MGs. With good marksmanship, you can easily kill planes with them, especially japanese planes that are very vulnerable. If you read again the accounts you did mention, the USAAF kept using the M2s because the US pilots had better marksmanship training, and it allowed them to obtain good results.

I don't understand what kind of efficiency you expect from these MGs. Could you be more precise at the effects you wait from them? I think you don't want them to be as deadly as the german 13mm HMGs for example, it would be funny, as it is much harder to kill anything with the Mausers than with the Brownings.

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

PlaneEater
05-26-2004, 03:41 PM
Hoarmurath, you're starting to pull the thread off-track--please try not to.

Here's basically what we're hoping for--or at least something comparable:

50 pct of hits within a circle of 2 mils (3.25 ft) diameter.
82 pct within a circle of 4 mils diameter (6.5 feet) diameter.
96 pct within a circle of 6 mils diameter (9.75 feet).

Hoarmurath
05-26-2004, 04:03 PM
ahem, can you point at the post where i was out of the topic?

Well, all the numbers you give are very interesting, i should debate on it, but the point is : Why do you think M2s are not deadly weapon at 250m? Personnally i find them deadly at more than 400m, most people i know online find them deadly at ranges from 0 to 500m. So what make you think they are not deadly enough at 250m?

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

PlaneEater
05-26-2004, 04:11 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
ahem, can you point at the post where i was out of the topic?
<HR></BLOCKQUOTE>

Right here:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Well, all the numbers you give are very interesting, i should debate on it, but the point is : Why do you think M2s are not deadly weapon at 250m? Personnally i find them deadly at more than 400m, most people i know online find them deadly at ranges from 0 to 500m. So what make you think they are not deadly enough at 250m?
<HR></BLOCKQUOTE>

This isn't about what I think about them, or what you think about them, or other people think about them.

It's an apparent numerical or data inconsistancy and error that's been isolated, is detrimental to both gameplay and historical accuracy, and needs fixing.

I would hope you would find those numbers a bit more than 'very interesting'.

Hoarmurath
05-26-2004, 04:29 PM
So, as this thread is intended to make things clear about the .50 issue, i will resume :

The M2 MGs are not modelled as accurately as other MGs in the game (no real proof http://ubbxforums.ubi.com/infopop/emoticons/icon_razz.gif ).

The M2 MGs are not deadly enough at range of about 250m (purely subjective http://ubbxforums.ubi.com/infopop/emoticons/icon_razz.gif ).

The M2 MGs in RL are better modelled than in FB/AEP according to USAAF studies (RL is overmodelled, be sure http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif )

I remember one post where Gibbage was saying Oleg told him the .50 M2 MGs were modelled the same as russian HMGs. Do you suggest it was a lie?

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

PlaneEater
05-26-2004, 04:37 PM
Ivan, cleanup on isle 5...

crazyivan1970
05-26-2004, 09:18 PM
You know what.... i`m getting tired of cleaning up...deleting is much better IMO or locking for that matter... if you can`t behave and act like adults... i`ll just get read of it. Simple as that.

Needless to say some of you showed a total disrespect to original poster and material that he presented - slipped into personal attacks and jepardized this thread. Sad.

V!
Regards,

http://blitzpigs.com/forum/images/smiles/smokin.gif

VFC*Crazyivan aka VFC*HOST

http://www.rmutt.netfirms.com/coop-ivan.jpg

http://www.rmutt.netfirms.com/vfc/home.htm

Kozhedub: In combat potential, the Yak-3, La-7 and La-9 fighters were indisputably superior to the Bf-109s and Fw-190s. But, as they say, no matter how good the violin may be, much depends on the violinist. I always felt respect for an enemy pilot whose plane I failed to down.

PlaneEater
05-26-2004, 09:58 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
You know what.... i`m getting tired of cleaning up...deleting is much better IMO or locking for that matter... if you can`t behave and act like adults... i`ll just get read of it. Simple as that.
<HR></BLOCKQUOTE>

I hear ya. I'm an assistant mod on my school's Animation Production Team board, and I know the pain.

We can't let one or two nitwits be grounds for locking or deleting an important thread like this, though. Best course of action is to trim the deadwood and keep the thread condensed to a quick reference for Oleg and a focused discussion.

EDIT: I guess I should stay on topic, too... Almost forgot to include the original question I wanted to ask.

For planes that mounted Brownings with the 45" heavy barrel rather than the 36" 'aircraft' barrel (P-47 wing guns, P-39 / P-63 nose guns, YP-80, P-38 gunpods, Spitfire wing guns), dispersion should be up to .3 or .4 mils less.

I also found some information on Browning .50s that are used for single-shot sniping, like the shot Carlos Hathcock made (2500 yards). They AREN'T modified. These are OFF THE SHELF Browning .50s, the only difference being the longer 45" 'heavy' barrel.

Aside from mounting a scope to the rear of the receiver, and maybe sandbagging it down extra, all that needs to be done to set a Browning .50 to single-fire is to turn the timing nut all the way to 'late' (from what I understand). This throws the timing of the gun's action off and results in it only firing once for every trigger press.

Some crews would also simply hand-load the gun between each shot, so they wouldn't have to re-time the weapon for automatic fire.

This completely discounts the argument that only heavily modified Browning .50s were capable of 1000 yard pinpoint shots...

[This message was edited by PlaneEater on Wed May 26 2004 at 09:44 PM.]

Gibbage1
05-26-2004, 10:12 PM
I think I am the 2nd nitwit. I wont let the trolls get me. Back onto the subject.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by PlaneEater:

I hear ya. I'm an assistant mod on my school's Animation Production Team board, and I know the pain.

We can't let one or two nitwits be grounds for locking or deleting an important thread like this, though. Best course of action is to trim the deadwood and keep the thread condensed to a quick reference for Oleg and a focused discussion.<HR></BLOCKQUOTE>

"Most P-39's were sent to the Russians - so I guess that was an American secret weapon against our Russian allies."

Stan Wood, P-38 pilot who also flew the P-39.

Hoarmurath
05-27-2004, 01:06 AM
ok then, as you quoted Blutarski in your initial post, i'll do the same :
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
According to a 1950 USAF fighter gunnery manual in my library, the M2 50cal in a rigid a/c mounting (wing or nose) firing in the air-to-air mode is credited with a 100 pct dispersion zone of 8 mils. In 1950 USAF parlance a mil is the apex angle formed by an isosceles triangle with sides 1000 ft long and a base of 1 foot. Stated in another way, 100 pct of shots fired by a single 50cal will strike within a circular area 8 feet in diameter at a range of 1000 feet (333 yards). At 500 meters (547 yards), the diameter of the circular area would be about 13 feet. <HR></BLOCKQUOTE>
if you read again, these numbers are for a single .50 MG, so you don't know for sure what amount of shaking you'll have when firing three or four .50 MGs. I'm not sure you realize what the recoil of these weapons is.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
According to the standard exterior ballistics law of distribution, at 500 meters the distribution of hits within that circle will be as follows:

50 pct of hits strike within a circle of 2 mils (3.25 ft) diameter.

82 pct of hits will strike within a circle of 4 mils diameter (6.5 feet) diameter.

96 pct of hits will strike within a circle of 6 mils diameter (9.75 feet).
<HR></BLOCKQUOTE>
ok, so we are speaking about a 500m convergence...
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
With a point convergence set at 547 yards / 500 meters (a very long range indeed for air to air), a battery of six 50cals firing a one second burst at that range would theoretically put 36 bullets out of 72 bullets fired into a area of 8.3 square feet (less than one square yard), i.e. - about 4 bullets per square foot.
<HR></BLOCKQUOTE>
Once again, this is theoretical accuracy of a single M2 applied to a battery of six HMGs.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Since hitting density varies inversely according to the square of the range, it can be seen that the same six guns firing at 250 meters point convergence would be quite deadly, depositing those same 36 hits within a circular area of 2 square feet, i.e. - about 18 bullets per square foot.
<HR></BLOCKQUOTE>
wrong, if you are before convergence range, your fire will be with more spreading. But ok, you want your MGs to be deadly at 250m, i understand.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
If you were watching a strafing run, with bullets striking the ground, over eighty percent of the bullets would be striking within the middle 50 percent of the bullet pattern width.
<HR></BLOCKQUOTE>
It's exactly what i did when seeing the "Thunderbolt" movie, i looked at the bullet pattern, and the area covered seemed to be fairly large.

and this time not from blutarski, but from you :
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
This completely discounts the argument that only heavily modified Browning .50s were capable of 1000 yard pinpoint shots...
<HR></BLOCKQUOTE>
err... i thought we were talking of a battery of .50 MGs firing at 500m convergence and not being deadly enough at 250m? What are you trying to tell, that you want your MGs to hit with deadly accuracy from more than 1000 yards range?
About them not being deadly enough at 250m range, i'm sorry but i don't agree, they are deadly at that range already.
About your post telling of firing at targets more than a kilometer away... Wasn't this thread supposed to stay serious?

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

PlaneEater
05-27-2004, 01:35 AM
ATTN: Blutarski--

Is there a chance you could scan the gunnery manual you have and send them to me? Oleg wants to see them.

VMF513_Sandman
05-27-2004, 05:56 AM
i have heard that the recoil of 8x50 cal guns blazing at once in the jugs would actually slow the plane down if the pilot didnt come in at full power. now seein as how the jug came in at roughly 10 tons, it would take a hell of alot of force to slow that puppy down like that. could it be that the 50 cal's as far as recoil (and hitting power) are just a tad off?

for a jug, having all 8 guns blazing should be almost the equivalent to 1 of the mk 108's of the 109's...not only does the 108 shake the cockpit like nothin, they'll blow apart anything. differnce is, the 50 cal's doesnt have the muzzle flash of the 108's...but they should still be capable of doing tremendous damage to whatever it hits.

what we need besides the dispursion adjusted, is brighter red (or even yellow) tracers that doesnt wink out 500 meters in front of the plane. what was said about the convergence is very true with wing mounted guns. the shells need to come together at a point. given bullet drop from wind resistance and gravity, wing guns wouldnt be quite as accurate at very long range...meaning, over 300 feet; compared to 4 guns set basically in a triangle in the p-38..along with the fact that the guns are nose mounted in the lightning. with this set-up, all the shells are concentrated in a cone pattern. in wing guns, the effect basically(when u factor in wind resistance) turns into a shotgun. but even a shotgun will tear it up if the range is close.
1 other thing...is it me, or do the bullets from the german/russian planes get to the target about 2 seconds sooner than the 50 cals at the same range? seems like it....u need about 2x's the lead-off in 50 cal mounted planes than the others.

ZG77_Nagual
05-27-2004, 08:58 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Since hitting density varies inversely according to the square of the range, it can be seen that the same six guns firing at 250 meters point convergence would be quite deadly, depositing those same 36 hits within a circular area of 2 square feet, i.e. - about 18 bullets per square foot.
<HR></BLOCKQUOTE>

Just a point here - 250 meters point convergence means just that - the convergence is set at 250 meters.
Planeeater - glad your in touch with Oleg - makes all the noise moot http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif Again, very well thought out and articulate observation based on science - not opinion.

Just to summarize what I seem to be seeing.

As I understand it - the issue is not with the dispersion area of the M2 per se (pretty darned close to 13 feet at 500 meters) - but with the distribution of hits within that area.

Also - relative to other similar weapons - in particular the japanese weapons which are historically less accurate.

These are separate because they involve two things - The M2 may be spot on dispersion area wise right now - but needs distribution tuning.

some of the the other 12.7s however may need to have their dispursion widened.

Hoarmurath
05-27-2004, 09:20 AM
ok, so finally we agree that the dispersion of the M2 is not that bad in FB... For the distribution of shots, i don't know, i haven't found how to check it in FB.

FYI, i was today able to disintegrate (no explosion, it just broke in many parts) a zero at 200m with a one second burst from the P38 MGs. As i often get such results with the P38 (i fly it a lot), you can understand why i don't find the .50 MGs to be that undermodelled.

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

ZG77_Nagual
05-27-2004, 09:54 AM
I don't think it was ever an issue of the m2 in an of itself - it was first it's relative performance - then Planeater came up with his statistical analysis. Nor is it strictly and issue of the guns performance in the simm.

To summarize - Gib started by showing a dramatic diff between the nose mounted m2 and other nose mounted 12.7s - in particular those on the ki84 which should be less accurate. Blutarski proposed that 13 feet at 500 meters range and convergence was about right for the total dispersion area for the M2 - I tested this in the 38 and found it to be very close.

Planeater examine the way hits are dispersed within the dispersion area and found what he thinks is a statistical flaw with the way rounds are distributed within that range.

Just to reiterate then - hypothesese would be

M2 dispersion area may be correct
M2 hit distribution within that area may not be correct (too random)

Other 12.7s may have undermodeled dispersion - the best argument for this being the 12.7s in the ki84 - which are currently within about 1 meter at 500 meters range and convergence.

Corrective measures would be -

Model hit distribution within dispersion radius according to a bell curve

De-tune the other 12.7s (keep in mind the vvs guns are known to be more accurate than the brownings - how much more is the question) and, presumably, also correct their dispursion.

This last if Oleg finds Planeater's argument to be true of course

p1ngu666
05-27-2004, 12:37 PM
yeah, the ubs brezin or whatever was a better gun in every respect i think by a little in each area, but that adds up http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

hoarmurath, your remark on good marksman ship makes me laugh.
a good marksman to me is a sniper, hitting a small target.
in fb with 50cal we NEED to get LUCKY to hit.
oh and compare the b239 nose guns to a 109 nose guns. im fed up of pointing out the obvious to u.

planeeater, great post and work, hats off to ya http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif. i think u may have missed some info from the threads, but it was a big undertaking todo this :|

oh and im with u on if the .50cal is like this, why are other guns so "perfect" http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

oh and i wanna know the per round power of the .50cal weapons, im wondering if the hitting power is overmodeled to make up for the spread

http://www.pingu666.modded.me.uk/mysig3.jpg
&lt;123_GWood_JG123&gt; NO SPAM!

p1ngu666
05-27-2004, 12:38 PM
ps, love the bell curve http://ubbxforums.ubi.com/images/smiley/16x16_smiley-happy.gif

http://www.pingu666.modded.me.uk/mysig3.jpg
&lt;123_GWood_JG123&gt; NO SPAM!

PzKpfw
05-27-2004, 12:40 PM
Concerning fireing the guns effect on flight velocity, the P-51D/K when all guns were fired, suffered an velocity loss of less then 1 mph.


Concerning tracers, Ie, the 357th FG did not use tracers; because the FG felt "it gave a false sense of distance and direction". They relied instead on 'steel cored' rounds that sparked on impact like 'winking lights'.

Regards, John Waters

---------
Notice: Spelling mistakes left in for people who need to correct others to make their life fulfilled.

----
The one that gets you is the one that you'll never see.
-----

----

"After 44 we called the new models the 'bumps', because every new model had another bump or hump on the fuselage, which naturally was particularly bad for the flight characteristics of the aircraft."

Walter Krupinski: on the Bf 109...
----

-----
"The damn Jerries have stuck their heads in the meatgrinder, and I've got hold of the handle."

Lt.Gen. George S. Patton, Jr. December 26, 1944.

------
"We've got the finest tanks in the world. We just love to see the German Royal Tiger come up on the field".

Lt.Gen. George S. Patton, Jr. Febuary 1945.

------
For Americans war is almost all of the time a nuisance, and military skill is a luxury like Mah-Jongg. But when the issue is brought home to them, war becomes as important, for the necessary period, as business or sport. And it is hard to decide which is likely to be the more ominous for the Axis--an American decision that this is sport, or that it is business."
--D. W. Brogan, The American Character

Blutarski2004
05-27-2004, 12:54 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by ZG77_Nagual:
I don't think it was ever an issue of the m2 in an of itself - it was first it's relative performance - then Planeater came up with his statistical analysis. Nor is it strictly and issue of the guns performance in the simm.

To summarize - Gib started by showing a dramatic diff between the nose mounted m2 and other nose mounted 12.7s - in particular those on the ki84 which should be less accurate. Blutarski proposed that 13 feet at 500 meters range and convergence was about right for the total dispersion area for the M2 - I tested this in the 38 and found it to be very close.

Planeater examine the way hits are dispersed within the dispersion area and found what he thinks is a statistical flaw with the way rounds are distributed within that range.

Just to reiterate then - hypothesese would be

M2 dispersion area may be correct
M2 hit distribution within that area may not be correct (too random)

Other 12.7s may have undermodeled dispersion - the best argument for this being the 12.7s in the ki84 - which are currently within about 1 meter at 500 meters range and convergence.

Corrective measures would be -

Model hit distribution within dispersion radius according to a bell curve

De-tune the other 12.7s (keep in mind the vvs guns are known to be more accurate than the brownings - how much more is the question) and, presumably, also correct their dispursion.

This last if Oleg finds Planeater's argument to be true of course<HR></BLOCKQUOTE>


Gentlemen,

Some thoughts -

WING SHAKE

There has been a great deal of discussion about "wing shake" and its presumed effect upon the dispersion charcteristics of wing mounted guns. Does anyone have any firm historical references which corroborate this? I have been through this USAF fighter gunnery manual from cover to cover and found no mention of the matter whatsoever. The manual discusses the problem of maintaining aim under high G conditions, the effects of different types of gunsights upon shooting accuracy, and a great deal about optimal sightlines, gun ranges, and gun harmonization patterns. But nothing is said about "wing shake" or "wing vibration". This leads me to believe that "wing shake" is either a non-existent issue in RL or of such minor consequence that the gunnery manual ignores it. If someone can produce some clear historical data to the contrary, then I will stand corrected. Until then I remain skeptical.


- - - - -


HARMONIZATION

For whatever it is worth, the following comes from the afore-mentioned fighter gunnery manual:

QUOTE -

HARMONIZATION OF THE F-51 AND THE F-47

1. Place a target with a 50-inch bull's-eye at a desired range from the aircraft. The target should be moveable laterally.

2. Raise the tail of the aircraft and place it on the tail stand.

3. Attach plumb bobs to the aircraft and align with the bull's- eye by moving the target laterally.

4. Place wing jacks under each wing and level the aircraft laterally and then level the aircraft longitudinally. Re-check the plumb lines and bull's-eye to ascertain that they are in alignment. Using a gunner's quadrant, make the desired mil setting. Place the quadrant on the longitudinal levelling lugs and raise or lower the tail until the quadrant is level.

5. Use a sight-line-level indicator to align the sight parallel to the flight path of the aircraft. First turn the sight on, permitting it to warm up for not less than 10 minutes. Place the sight-line-level indicator in alignment with the pipper of the sight. Next, make a vertical adjustment of the sight to cause the bubble, the index, and the pipper to be aligned with each other.

6. Leave the sight on. Remove the sight-line-level indicator from the sight. Align the sight with the top of the bull's-eye by lowering or raising the tail of the aircraft. Align the sight on the bull's-eye laterally by using the notches on the base of the sight. Check to see that the plumb lines are aligned with the bull's-eye.

7. Align the gun with the target. In firing the guns, adjustment is necessary to cause the guns to shoot into the bull's-eye.

- UNQUOTE.

This, IIUC, describes a point harmonization preocedure.


- - - - -


DISPERSION

If the dispersion issue we have observed IN fb is indeed related to an incorrect distribution of strikes within the 100 pct dispersion zone, one POSSIBLE solution to consider is to reduceg the diameter of the dispersion zone from 8 mils to 4 mils and simultaneously reduce the RoF to 80 pct of normal. Consider the relationships of bullet strikes versus area in relative terms:

0-2 mil diameter; density factor of 50
2-4 mil diameter; density factor of 10
4-6 mil diameter; density factor of 3
6-8 mil diameter; density factor of 0.6

This would produce approximately the correct density of hits within the 4 mil zone. If I've done my math correctly, the area outside of 4 mils could be reasonably disregarded. Just a thought.


- - - - -


To PlaneEater - I'll see what I can do.

BLUTARSKI

Hoarmurath
05-27-2004, 05:11 PM
Pingu, i think i already told you elsewhere. The fact that YOU can't hit a barn door with M2s doesn't necessary mean they are badly modelled... Especially when you are complaining for too much spreading, if you can't hit with them now, you will hit even less if spreading is reduced.

Personnally, i'm not a good shooter, with other planes guns i need to be very, very close to hit other fighters. But i have no such problems with P40, P51, P47, P38, Buffalo, well, any plane equiped with M2s. I like them because i can hit targets much more easily, even in deflection shooting.

Blutarski, it is not only the wing that is shaking, but the whole plane (the wing is too, i assure you)... What you describe is a plane being on ground, so, very stable... Planes aren't very stable, even when they are not firing, because the air isn't still. If you try to have airborne accuracy equal to ground tests accuracy, the result will be very, very far from being realistic.

For the spreading, i tried to have a look at the pattern by shooting in water (impacts stay longer and are easier to spot than on ground). It seem that the distribution of impacts is in fact aleatory, and not bell shaped. But well, i tried with other MGs in the game and had the same result, they seem to be all modelled this way.

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

TBS_TWIGTOTO
05-27-2004, 06:38 PM
I believe that the "hit bullets" that actually damage planes from the 50 calibers might be too strong - it takes about 25-50 bullets/kill on average over a range of convergences and deflections and enemy A/C types.

However, it take nominally 500-1200, avg about 900 bullets fired/kill over the same range - and historically, WW2 after action combat reports average about 200 bullets fired/kill (they didnt' count "hit bullets ).

So - better dispersion is justified, historically.

I fear that if the dispersion gets the 4x improvement that is warranted from historical data, that, the number of kills/sortie with the P51's will rise dramatically - ie, if it takes now 50hit/1000 fired - then when it goes to 50hit/250 fired - ie still only 25% of bullets hitting the target AFTER a 4x dispersion improvement - there will be a lot of sqeauling when P51's are wiping out planes wings, fuses and starting wing fires as they and similarly gunned Hellcats, P47's often achieved in WW2.

There is a lot of data to get a statistically significant set of facts on 50 calibers shot/kill... so you can set an "average" shot/kill ratio close to historical. I think this is a useful and data-related approach for machine guns which fire more rounds/kill, but have more to fire than cannons - The cannon rounds/kill are easier to do the (K.E./round - Plane damage model) equation ...

http://www.cebudanderson.com/images/carsondoc.gif

http://www.cebudanderson.com/images/firstkilldoc.gif

http://www.cebudanderson.com/images/obeedoc.gif

http://www.cebudanderson.com/images/braleydoc.jpg

and more.. I don't any logical reason not use the statistical data of many combat reports to build the "fire bullet/kill" ratio.

http://www.cebudanderson.com/images/bochkaydoc.gif

" Aggressiveness was a fundamental to success in air-to-air combat and if you ever caught a fighter pilot in a defensive mood you had him licked before you started shooting ": Captain David McCampbell, USN, leading U.S. Navy ace in W.W.II, who holds the record for 9 air to air fighter kills in one sortie in 1800 round 50 caliber Hellcat

ZG77_Nagual
05-27-2004, 06:49 PM
The bell curve is a mathematical model rendered in two dimensions to explain statistical behavior - it does not translate literally into a 'bell-shaped hit pattern' In this case - it would show a higher concentration of hits in the center of the dispersion zone than currently occurs. It's a statistical model which has been expressed other ways in this thread - such as saying 'x percentageof bullets ' in the first three feet from center 'y' in the next etc.,
that's one issue.

the second is the diff between m2 spread and the spread of other 12.7mm guns in the game. If you've done the water test you've seen this.

For example the p38 and ki84 below

http://pws.chartermi.net/~cmorey/pics/kidisp.jpg

http://pws.chartermi.net/~cmorey/pics/dispurs.jpg

So - once again - the bell-curve is used to model the statistical behavior - in this case - of bullets striking in a circular area (dispersion zone) in terms of how they are concentrated - statistically more toward the center - with less toward the fringes. Planeater's argument is simply that they do not behave this way. Separate from that is the question of relative dispersion between different guns. As illustrated in the above screenshots - which show the ki and p38 both partially submereged near the marks made by short bursts from from the machine guns only on both aircraft ffrom 500 meters. Only horizontal dispersion is valid here as there was some very slight vertical movement.

Gibbage1
05-27-2004, 07:27 PM
Your going off topic again. Please stop trolling this thread.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Hoarmurath:
Pingu, i think i already told you elsewhere. The fact that YOU can't hit a barn door with M2s doesn't necessary mean they are badly modelled... Especially when you are complaining for too much spreading, if you can't hit with them now, you will hit even less if spreading is reduced.<HR></BLOCKQUOTE>

"Most P-39's were sent to the Russians - so I guess that was an American secret weapon against our Russian allies."

Stan Wood, P-38 pilot who also flew the P-39.

Hoarmurath
05-28-2004, 02:33 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Gibbage1:
Your going off topic again. Please stop trolling this thread.

<HR></BLOCKQUOTE>

gibbage, you should stop speaking to yourself....

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

PlaneEater
05-28-2004, 03:37 AM
Hoarmurath, please leave and make sure the door doesn't hit you on the way out. I'd feel bad for the door.

Everybody else, just ignore him. Compeltely. Like Galen Thurber.


Blutarski, does the manual you have specify whether those figures are for the 36 or 45 inch barrel? Or would there be much difference at those ranges?

Blutarski2004
05-28-2004, 08:06 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by PlaneEater:
Blutarski, does the manual you have specify whether those figures are for the 36 or 45 inch barrel? Or would there be much difference at those ranges?<HR></BLOCKQUOTE>


..... The fighter gunnery manual does not specify barrel length, only M2/M3 50cal Browning aircraft machine gun. Based upon other reading, I am assuming that we are discussing the 36-inch barrel. Firing M2 AP cartridges, the difference in muzzle velocity between the 36-inch and 45-inch barrel versions is 100 fps (2835 fps versus 2935 fps). This is only about 3.5 percent difference, which I would not consider meaningful.

BLUTARSKI

Blutarski2004
05-28-2004, 08:22 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Hoarmurath:
Blutarski, it is not only the wing that is shaking, but the whole plane (the wing is too, i assure you).

..... I don't disagree with what you say. My point is only that no one has produced any convincing proof or evidence that the actual bullet dispersion of wing-mounted guns are any more affected than nose mounted guns by such movement of the aircraft.


What you describe is a plane being on ground, so, very stable... Planes aren't very stable, even when they are not firing, because the air isn't still. If you try to have airborne accuracy equal to ground tests accuracy, the result will be very, very far from being realistic.

..... Again, I do not disagree with what you say. Unpredictable or eccentric movements of the a/c in flight will produce an AIMING problem rather than a DISPERSION problem (not "yelling" with capitals, only emphasizing).


For the spreading, i tried to have a look at the pattern by shooting in water (impacts stay longer and are easier to spot than on ground). It seem that the distribution of impacts is in fact aleatory, and not bell shaped. But well, i tried with other MGs in the game and had the same result, they seem to be all modelled this way.

..... You may well be correct. The question in my mind is why the M2 50cal appears to show such different dispersion characteristics than other 50cal/12.7mm type HMG,s in the sim.

http://hoarmurath.free.fr/<HR></BLOCKQUOTE>

BLUTARSKI

WWMaxGunz
05-28-2004, 10:03 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Blutarski2004:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by PlaneEater:
Blutarski, does the manual you have specify whether those figures are for the 36 or 45 inch barrel? Or would there be much difference at those ranges?<HR></BLOCKQUOTE>


..... The fighter gunnery manual does not specify barrel length, only M2/M3 50cal Browning aircraft machine gun. Based upon other reading, I am assuming that we are discussing the 36-inch barrel. Firing M2 AP cartridges, the difference in muzzle velocity between the 36-inch and 45-inch barrel versions is 100 fps (2835 fps versus 2935 fps). This is only about 3.5 percent difference, which I would not consider meaningful.

BLUTARSKI

<HR></BLOCKQUOTE>

You have to have more powder in the cartriges to get the full benefit of a longer barrel at least if the cartriges were made for the shorter one.


Neal

PlaneEater
05-28-2004, 01:12 PM
The original design used the 45" barrel, and the 12.7x99 BMG round was designed for that, so the standard 'ball' rounds are probably slightly overloaded for a 36" barrel.

Probably doesn't hurt anything... except the target...

Gibbage1
05-28-2004, 02:28 PM
Blutarski. Please ignore Hoarmurath. He is trolling again. He is trying to prove that the M2 .50 cal does not have any differant a dispersion then other similar guns in the game. Everyone but him can see clearly that the .50 cal M2 has a much much wider dispersion then the other 12.7mm guns like the UBs and others.

Blutarski, thank you for your contributions to this topic.

Gib

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Blutarski2004:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Hoarmurath:<HR></BLOCKQUOTE>
<HR></BLOCKQUOTE>

"Most P-39's were sent to the Russians - so I guess that was an American secret weapon against our Russian allies."

Stan Wood, P-38 pilot who also flew the P-39.

PlaneEater
05-29-2004, 05:24 AM
Blutarski, what's the name / designation of the manual you have? I may be able to obtain a copy or something very similar locally.

PlaneEater
05-30-2004, 10:18 PM
I have put together a visual representation of the difference between IL-2's dispersion system and how real gunfire disperses.

A recap of how IL-2 disperses shots:

IL2 uses a random X,Y offset when a weapon is fired. The dispersion is a range between 'A', the amount of dispersion for the first shot fired, and 'B', for when the gun is firing a long burst and the maximum possible amount of recoil dispersion is reached.

For *all* the guns in the game, when they are fired, the game looks up the dispersion value for the current amount of recoil, and creates a random X,Y coordinate within the grid the recoil value creates, like this:

http://home.mindspring.com/~snakebitt/grid_extents.jpg

This creates the square shaped gun-hit patterns in game, like this one:

http://mitglied.lycos.de/jaytdee/fbg/b2392.jpg

This is how IL-2's variable-grid-sized (X,Y) coordinate offset system disperses gunfire. Notice how, since the values are random coordinates, any given shot has equal probability of landing ANYWHERE in the grid:
http://home.mindspring.com/~snakebitt/randXY_disperse.jpg

This is how gunfire disperses in real life (bell-curve distribution), where the probability of a shot hitting a spot X drops as the distance from the center increases:
http://home.mindspring.com/~snakebitt/sigma_disperse.jpg

Aaron_GT has a code segment solution, that uses a very close histogram approximation out to 4 sigma to simulate bell-curve distribution in gunfire:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Aaron_GT
Shouldn't be too hard to change in the code - C++ has plenty of maths libraries. I suppose there might conceivably be an issue with speed of the library and licensing of fast libraries, but a workaround that is closer to a normal distribution could be knocked up and be made to work fast. If you had a dispersion pattern going out to 4 sigma you could use a histogram rather than continuous function and get a pretty good approximation.

E.g. for x dispersion

int h = (int)floor(8 * drand48());
double delta = disperion[h] + boxWidth*drand48() - boxWidth/2;
double r = 2*PI*drand48();
x = x + delta*sin(r);
y = y + delta*cos(r);

And you can simplify the sin and cos with
LUTs too.
<HR></BLOCKQUOTE>

This is just too critical to leave out. Aerial gunnery is too huge a part of the game to leave this flaw in.

To be perfectly honest, I think once this is fixed, we'll find Oleg has the values for the Browning's dispersion decently close to correct.

Spectre-63
05-31-2004, 07:34 AM
The amount of research you've put into this is absolutely awesome, PlaneEater. I'm anxiously awaiting the results of your efforts on our behalf. http://ubbxforums.ubi.com/images/smiley/11.gif

http://home.comcast.net/~mjmcmahon672/images/Sig_Small.gif

Diablo310th
05-31-2004, 08:37 AM
Guys.....you are doing a super job of research. Gibbage or anyone..has Oleg said anything about teh new findings? Is he considering any changes? On the down side....if this coding is changed could someone use this info. and hack this particular part of teh game???

http://img54.photobucket.com/albums/v166/310thDiablo/Diablos20Sig.jpg

Gibbage1
05-31-2004, 12:52 PM
Nothing new yet. I asked mid last week but no reply yet.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Diablo310th:
Guys.....you are doing a super job of research. Gibbage or anyone..has Oleg said anything about teh new findings? Is he considering any changes? On the down side....if this coding is changed could someone use this info. and hack this particular part of teh game???

http://img54.photobucket.com/albums/v166/310thDiablo/Diablos20Sig.jpg <HR></BLOCKQUOTE>

"Most P-39's were sent to the Russians - so I guess that was an American secret weapon against our Russian allies."

Stan Wood, P-38 pilot who also flew the P-39.

Hoarmurath
05-31-2004, 02:33 PM
The amount of whining in this thread is incredible... You began the whining by complaining that the .50 M2 were not modelled as the other HMG in the game, and finally, yuou finish complaining about how the M2s are not modelled as you think they should with a single chart you present as if it was the holy bible of MG spreading. What of the difference between the other HMG spreading and your chart? not a word. Not very surprising, as it was already clear that the HMG in the game are modelled the same way. FYI, russian, japanese, and americans .50 cal HMG have the same range, i was quite surprised as i found that they had not so different characteristics. The bullets also have approximately the same the same trajectory, losing slightly more than 50m of height at 1000m. And they have the same spreading pattern. But of course, you made so many tests that you already had seen by yourself these similarities, hadn't you?

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

F16_Fatboy
05-31-2004, 03:13 PM
I recently received the 1944 documentary movie "The Fighting Lady". Some very good gunnery film shows Hellcats (as I assume) attacking planes, ground objects and ships, destroyers disappears in a hail of bullets as they are strafed with 6 x.50. Narrator gives the convergence distance to 300 yards. This is the final proof and all we need! Let´s try and post some real life screen shots and film clips in order to put this thoretical debate to an end! As soon as I find out how to I will be back with some.

FLSTF

http://img41.photobucket.com/albums/v125/F16_fatboy/Album1/sig_fatboy.jpg

Menthol_moose
05-31-2004, 04:59 PM
keep up the good work boys, and ignore the luftwhinger http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

ZG77_Nagual
05-31-2004, 05:18 PM
Nicely done.

Hoarmuth - I'm begining to think you don't understand what's being said here - this is not whining - it's math.

these guys have found what they think may be flaws in the PHYSICS MODELING OF PROJECTILE DISPERSION and have made some very constructive suggestions for correcting it. No-one is getting emotional or personal about it.

The chart is just another visual representation of what is being discussed -

First there was a simple statement of percentages -
Then a bell curve illustration - which you seem to have understood literally as meaning the bullets should make a 'bell shaped pattern' -
Next we have a more literal visual representation designed to show how bullets work in real life as distinct from how they appear to work in the game. It's all quite a systematic way of illustrating the point - probably one of the most lucid presentations I've seen.

On top of that we have actual coding suggestions for modeling the dispersion with greater fidelity.

Oleg has been receptive to this kind of input before - in fact most of it was somewhat less precise than this - but sufficient to compel him to reconsider and even modify some in game behavior.

In Point of fact this is precisely the kind of presentation that Oleg has asked for from users on a number of occasions.

This thread is an example of exactly what this board was created for. It might help you to better understand this if you were to go over some of Oleg's posts on the subject of modeling corrections.

[This message was edited by ZG77_Nagual on Mon May 31 2004 at 04:30 PM.]

Hoarmurath
05-31-2004, 06:08 PM
Sorry nagual, but this is whining... At first, they were complaining about the difference between how M2s and other HMGs were modelled... Now that we have established there is actually no big difference about how the different HMGs are modelled, they have switched to a whining about how M2s are modelled differently than IRL... Why not?

But then aren't all HMGs badly modelled, and not only M2s? What make M2s so special that they should be modelled differently then other HMGs?

And especially, what make the M2s impossible to use in your opinion? You can bring your hellcat guncam footage, no problem, don't you remember i already gave here a link to a P47 guncam footage? Do you think this footage wasn't adequate? Why? What will make the footage of hellcats different?

I think that Luthier was right, you will not be happy until your M2s volleys are capable of disintegrating other ennemy planes with only a few hits. And this attitude is not called math, it's called whining.

http://hoarmurath.free.fr/images/sighoar.jpg (http://hoarmurath.free.fr/)

PlaneEater
05-31-2004, 06:13 PM
For the last time, folks, don't feed the troll.

Ignore him and he will go away.


Oleg stated in an email that they will look at the Ho-103 again, and that is probably needs to be changed to be similar to the Browning.

I personally have a strong suspicion that if bell-curve dispersion is implemented, we'll find the Browning is pretty dead on. It's the overly-random dispersion system that is hobbling it.

Gibbage1
05-31-2004, 06:20 PM
You are very much wrong. There is a HUGE differance between the spread of M2 .50 cal and other HMG's in the game. Your eather just trolling, or so ignorant you cant see the truth. YOU are the ONLY one on this forum that cant admit there is a big differant in dispersion between the M2 and others. Even Oleg admits it!!! Your flawed test's prove NOTHING.

Your doing nothing but trolling, and I would like you to STOP.

First you ask us to prove the spread, we did. Then you say ground testing is invalid so we did it in the air. You never replied to those test's, and made your own screenshots that proved nothing more then the fact you know how to make a screenshot. Then you have guncam footage of a P-47 with 8 wing guns firing at ground targets out of convergance as "proof" that 2 nose mounted guns should have the same dispersion. Now your in here trying to take the topif off track after you have been asked many times to leave.

I will ask you this once more. Please leave and stop trolling the .50 cal threads. Its a proven fact that the .50 cal M2 spread is much greater then other HMG's. That topic is dead. Get over it. Now its a debate as to if its historic and what we can do to fix the differance.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Hoarmurath:
Sorry nagual, but this is whining... At first, they were complaining about the difference between how M2s and other HMGs were modelled... Now that we have established there is actually no big difference about how the different HMGs are modelled.
<HR></BLOCKQUOTE>

"Most P-39's were sent to the Russians - so I guess that was an American secret weapon against our Russian allies."

Stan Wood, P-38 pilot who also flew the P-39.

ZG77_Nagual
05-31-2004, 06:31 PM
this is my last run at this http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif &lt;applause&gt;
There are two issues -

1&gt;M2 RELATIVE to other guns - particularly the ki84s 12.7 which, by all accounts,was a bad knockoff of the m2. It has been conceded the vvs 12.7s were more accurate than the m2 - question of degree there.

(M2 dispersion AREA has been shown to probably be about right for the M2 - in and of itself - again the question is relative to OTHER guns which show dramatically less AREA of dispersal)

2&gt;Dispersion modeling itself - across ALL guns - has been called into question - that argument has been very well documented with very clear illustrations and recommendations - per Oleg's criteria. Here the question is not RELATIVE AREA OF DISPERSION (see 1 above) but how individual bullets are DISTRIBUTED within that are.

So - simply put - two issues - RELATIVE DISPERSION and HOW DISPERSION IS MODELED. Two SEPARATE issues. &lt;thankyou, thankyou - and now, ladies and gentlemen our main show tonight: LORD OF THE DANCE! Featuring music by Yanni! and John Tesch!&gt;

Gibbage1
05-31-2004, 08:48 PM
Thank you for understanding the thread and puting it in plain words.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by ZG77_Nagual:
this is my last run at this http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif &lt;applause&gt;
There are two issues -

1&gt;M2 RELATIVE to other guns - particularly the ki84s 12.7 which, by all accounts,was a bad knockoff of the m2. It has been conceded the vvs 12.7s were more accurate than the m2 - question of degree there.

(M2 dispersion AREA has been shown to probably be about right for the M2 - in and of itself - again the question is relative to OTHER guns which show dramatically less AREA of dispersal)

2&gt;Dispersion modeling itself - across ALL guns - has been called into question - that argument has been very well documented with very clear illustrations and recommendations - per Oleg's criteria. Here the question is not RELATIVE AREA OF DISPERSION (see 1 above) but how individual bullets are DISTRIBUTED within that are.

So - simply put - two issues - RELATIVE DISPERSION and HOW DISPERSION IS MODELED. Two SEPARATE issues. &lt;thankyou, thankyou - and now, ladies and gentlemen our main show tonight: LORD OF THE DANCE! Featuring music by Yanni! and John Tesch!&gt;<HR></BLOCKQUOTE>

"Most P-39's were sent to the Russians - so I guess that was an American secret weapon against our Russian allies."

Stan Wood, P-38 pilot who also flew the P-39.

VMF513_Sandman
06-01-2004, 05:35 AM
very nice work plane eater. u obviously did alot of research into this. looking at the 'dust pattern', if u are at rather long range with the 50's, it almost appears to give a shotgun pattern. only if u are close...under 190 meters it seems, will u have a very tight and potent group.

WOLFMondo
06-01-2004, 05:46 AM
This might be considered a dumb/stupid response to this thread or simply not acheivable (so please delete if so) but has no one thought to find examples of these different aircraft that use 0.50's, ask there owners if they can be used in a test, set the guns up as per the instructions and actually fire them as they would have done when calibrating them IRL during the war and record this using whatever methods that are needed to clear this up once and for all?

http://bill.nickdafish.com/sig/mondo.jpg
Wolfgaming.net. Where the Gameplay is teamplay (http://www.wolfgaming.net)

PlaneEater
06-01-2004, 09:52 AM
Mondo: ownership of full automatic .50 caliber weapons is heavily restricted in the US--except for a few collectors and other folks, the only people who have M2s are the military.

Mounting guns on planes is, I believe, illegal except for law enforcement and military duties.

Blutarski2004
06-01-2004, 11:09 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by PlaneEater:
I have put together a visual representation of the difference between IL-2's dispersion system and how real gunfire disperses.

A recap of how IL-2 disperses shots:

IL2 uses a random X,Y offset when a weapon is fired. The dispersion is a range between 'A', the amount of dispersion for the first shot fired, and 'B', for when the gun is firing a long burst and the maximum possible amount of recoil dispersion is reached.

For *all* the guns in the game, when they are fired, the game looks up the dispersion value for the current amount of recoil, and creates a random X,Y coordinate within the grid the recoil value creates, like this:

http://home.mindspring.com/~snakebitt/grid_extents.jpg

This creates the square shaped gun-hit patterns in game, like this one:

http://mitglied.lycos.de/jaytdee/fbg/b2392.jpg

This is how IL-2's variable-grid-sized (X,Y) coordinate offset system disperses gunfire. Notice how, since the values are random coordinates, any given shot has equal probability of landing ANYWHERE in the grid:
http://home.mindspring.com/~snakebitt/randXY_disperse.jpg

This is how gunfire disperses in real life (bell-curve distribution), where the probability of a shot hitting a spot X drops as the distance from the center increases:
http://home.mindspring.com/~snakebitt/sigma_disperse.jpg

Aaron_GT has a code segment solution, that uses a very close histogram approximation out to 4 sigma to simulate bell-curve distribution in gunfire:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
_Aaron_GT_
Shouldn't be too hard to change in the code - C++ has plenty of maths libraries. I suppose there might conceivably be an issue with speed of the library and licensing of fast libraries, but a workaround that is closer to a normal distribution could be knocked up and be made to work fast. If you had a dispersion pattern going out to 4 sigma you could use a histogram rather than continuous function and get a pretty good approximation.

E.g. for x dispersion

int h = (int)floor(8 * drand48());
double delta = disperion[h] + boxWidth*drand48() - boxWidth/2;
double r = 2*PI*drand48();
x = x + delta*sin(r);
y = y + delta*cos(r);

And you can simplify the sin and cos with
LUTs too.
<HR></BLOCKQUOTE>

This is just too critical to leave out. Aerial gunnery is too huge a part of the game to leave this flaw in.

To be perfectly honest, I think once this is fixed, we'll find Oleg has the values for the Browning's dispersion decently close to correct.<HR></BLOCKQUOTE>


PlaneEater,


Excellent post. Thank you. Would love to see Aaron GT's code incorporated into FB ballistics. It would improve the realism of ALL the guns in the sim.


As regards your question re manuals, the one in my possession is -

AF Manual 335-25: FIGHTER GUNNERY - Rocket Firing, Fighter Bombing.
Department of the Air Force
Department of the Air Force, Washington, 1950
(superceding AFM's 335-25 May 1945, 335-30 February 1946, and 340-5 October 1944)

BLUTARSKI

Blutarski2004
06-01-2004, 11:12 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Hoarmurath:
Sorry nagual, but this is whining... At first, they were complaining about the difference between how M2s and other HMGs were modelled... Now that we have established there is actually no big difference about how the different HMGs are modelled, they have switched to a whining about how M2s are modelled differently than IRL... Why not?

But then aren't all HMGs badly modelled, and not only M2s? What make M2s so special that they should be modelled differently then other HMGs?

And especially, what make the M2s impossible to use in your opinion? You can bring your hellcat guncam footage, no problem, don't you remember i already gave here a link to a P47 guncam footage? Do you think this footage wasn't adequate? Why? What will make the footage of hellcats different?

I think that Luthier was right, you will not be happy until your M2s volleys are capable of disintegrating other ennemy planes with only a few hits. And this attitude is not called math, it's called whining.

http://hoarmurath.free.fr/<HR></BLOCKQUOTE>


You apparently miss the entire point of this discussion.

BLUTARSKI

crazyivan1970
06-01-2004, 11:55 AM
I would like to ask participants of this thread to stay on the subject and provide hard core data, not personal impressions. I just want this to go away, so lets make it happened.

Hoarmurath - with all due respect Sir, you are not helping right now.

Gibb, please avoid personal references...

Thanks.

V!
Regards,

http://blitzpigs.com/forum/images/smiles/smokin.gif

VFC*Crazyivan aka VFC*HOST

http://www.rmutt.netfirms.com/coop-ivan.jpg

http://www.rmutt.netfirms.com/vfc/home.htm

Kozhedub: In combat potential, the Yak-3, La-7 and La-9 fighters were indisputably superior to the Bf-109s and Fw-190s. But, as they say, no matter how good the violin may be, much depends on the violinist. I always felt respect for an enemy pilot whose plane I failed to down.

VMF513_Sandman
06-01-2004, 07:40 PM
in the us, ownership of any fully automatic weapons; doesnt matter if it's ak-47 and other assault rifles, or heavy machine guns like the m2, are strictly verbotten without a federal firearms license. and having a heavy machine gun like the 50 cal would be highly illegal unless u were serving in the military. even gun ownership in the us is gettin more and more restricted now vs 20 or 30 yrs ago and mounting any gun on a vehicle is a pipe dream.

i dont think 50 caliber tracer fire would be as faint as they are in fb tho. the tracers of the zero's are 3x's brighter than the 50's.

Gibbage1
06-02-2004, 12:00 AM
I have read that the US .50 cal M2 tracer round had a VERY low ammount of incendary fuel. Sometihng like 5 grams compaired to 40 on UBS? (I cant find the artical i was reading, so my numbers may be way off). So not only was the tracer dim, but it would go out in like 300-400 yards. I think Oleg modeled this well. Shooting anything using M2's over 300 yars WONT light them. Not even a Zero. Because the tracer goes out! Use a UBS with a very long tracer and it will light.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by VMF513_Sandman:
in the us, ownership of any fully automatic weapons; doesnt matter if it's ak-47 and other assault rifles, or heavy machine guns like the m2, are strictly verbotten without a federal firearms license. and having a heavy machine gun like the 50 cal would be highly illegal unless u were serving in the military. even gun ownership in the us is gettin more and more restricted now vs 20 or 30 yrs ago and mounting any gun on a vehicle is a pipe dream.

i dont think 50 caliber tracer fire would be as faint as they are in fb tho. the tracers of the zero's are 3x's brighter than the 50's.<HR></BLOCKQUOTE>

"Most P-39's were sent to the Russians - so I guess that was an American secret weapon against our Russian allies."

Stan Wood, P-38 pilot who also flew the P-39.

Gibbage1
06-02-2004, 12:14 AM
Im not promoting another game. Just a comparison.

I was trying to find the artical that mentioned the tracer rounds on .50 cals and found this.

http://www.netaces.org/ahweapons/us-brit/m2-50-600.gif

Please note a few things.

#1, this is a test from Aces high. A video game. Im in NO WAY saying they are accurate in the ammount of spread.

#2, there is no referance so we dont know how wide those rings are, or how far the spread is. Its useless as proof of anything.

#3, how the spread is. This is what PE is talking about. A concentration of bulletes in the center. The far far bulletes that went astray may very well be 13 feet, but the bulk of the bulletes are within a much tighter pattern.

I honestly think Oleg could not, or even would not fix FB to do this at this point in time. It would be a GREAT deal of work for him on a product that is reaching its end quickly.

I would however would love to see this sort of disperion in PF or BOB for all weapons if Oleg truly want to make this game as accurate as possible.

If its not possible to model the dispersion in this way, then why not ajust the US weapons to spray in at least the 50% margin and not the 100%? That way the game could at least be closer to historical.

"Most P-39's were sent to the Russians - so I guess that was an American secret weapon against our Russian allies."

Stan Wood, P-38 pilot who also flew the P-39.

Aaron_GT
06-02-2004, 01:40 AM
"Excellent post. Thank you. Would love to see Aaron GT's code incorporated into FB ballistics. It would improve the realism of ALL the guns in the sim."

Well I'd like it to be checked first! I've spotted some issues with it already! it was a quick 'off the top of my head' piece of code.


double delta = disperion[h] + boxWidth*drand48() - boxWidth/2

should be

double delta = disperion[h] + boxWidth[h]*(drand48()-0.5)

1. The normal distribution is symmetrical. You can economise on the number of elements in the look up table (LUT) but you would have more calculations at the expense of a tiny bit of extra memory - better to use the larger LUT.

2. To make my code work you need a series of boxes such that the area under each box is equal (equal probability of the result being in this range). So you'd want more than 8 boxes, of variable widths.

3. Rather than using sin and cos a look up table for each would be faster and good enough. It would be a case of profiling the code.

Since Oleg writes the stuff in Visual C++ then drand48() wouldn't be the correct function, but it works for GNU's c++.

I'll convert the fragment into visual studio and generate the box widths required to replicate a normal distribution, check it all, and get it emailed to Oleg for the weekend, if people think that is worth doing.

PlaneEater
06-02-2004, 02:21 AM
Please do! I didn't spot those. My coding experience is mostly simple VB, UnrealScript and a C derivitive called BOS.

Definitely clean it up and email Oleg. If you could throw together a quick Monte Carlo simulation with it, too, that'd rock.

Aaron_GT
06-02-2004, 06:22 AM
Yep, Monte Carlo would be part of the plan, and then plot the results alongside a normal distribution of the same sigma, and a straight uniform distribution.

Diablo310th
06-03-2004, 08:37 AM
Ohh wow guys...please clean it all up and send to Oleg. Maybe we could get this all into teh next patch.

http://img54.photobucket.com/albums/v166/310thDiablo/Diablos20Sig.jpg

WWMaxGunz
06-03-2004, 10:14 AM
There are places in the US that have the MMG's and HMG's, even mortars and
light cannon under private license and large ranges to use them. People
rent time on them to use them under some supervision and help. Last one I
saw on a news kind of show was in South Carolina. I expect that there must
be at least one in Colorado. It helps little since where will you find any
in aircraft mounts?

I for one can't see why Luthier doesn't find the other in-game 12.5's to be
entirely too focussed if he made the statement Hoarmurath credits him with.

Aaron, I bet the dispersion isn't bell distribution just because of the CPU
overhead. Even a circular distro would involve a lot (graph as semicircle).
Using a LUT of scaled results would be faster if the random returned an
integer with the maximum as the number of table elements. Any kind of check
for range (if under this then that, else if under next range then...) would
also slow the process miserably. The result would be dispersion as a set of
nested squares but with a lot of them mostly towards center it wouldn't be
any less 'real' than now. 101 8-bit FP's would fit in 1k and provide for
randoms 0% to 100%, the LUT results would make the 'curve' and give angles
in one operation.


Neal

Aaron_GT
06-04-2004, 05:05 AM
Neal,

What I'll do is the following:-

1. Model a histogram approximation of a normal distribition.
2. Do monte carlo simulations of my code compared to an actual normal distribution and the flat distribution we have now.
3. Time the each of the codes.

Then we can show a tradeoff of closeness to the normal distribution against speed of code.

Aaron_GT
06-04-2004, 05:06 AM
"sing a LUT of scaled results would be faster if the random returned an
integer with the maximum as the number of table elements."

That's what the Win32 random function does. I've more of a UNIX background so I wrote it in terms of drand48(). There probably isn't that much difference under the hood, though.

Aaron_GT
06-04-2004, 05:11 AM
" Any kind of check
for range (if under this then that, else if under next range then...) would
also slow the process miserably."

Hence using a LUT in my code to determine
which 'box' it should be in, but...

"The result would be dispersion as a set of
nested squares but with a lot of them mostly towards center it wouldn't be
any less 'real' than now."

That would be a better solution
than the one I suggested as it would be much
faster. All that is needed is the initial
calculation to create the map of squares which
would be done once, then fixed in the code.

Good call, Neal. I'll work this up at the weekend as a little piece of cross-platform code so I can do the profiling on Linux and then send it to Oleg for direct compilation into Windows.

Aaron_GT
06-04-2004, 06:46 AM
Ok some quick calcs on a 1GHz machine.

Each figure is the average time for 1
dispersion calculation in seconds to 1 sig fig

Uniform distribution: 3x10e-7
My original code: 9x10e-7
As above, sin, cos as LUTs: 6x10e-7
Neal's single random number code, with uniform random distribution within this: 6x10e-7
Neal's single random number, with just a lot of 'boxes' but no randomness within that: 3x10e-7

So basically with a set pre-cooked x and y dispersions and enough 'boxes' the code will be as fast as what is there now, but model the normal distribution nicely.

At the weekend I'll do some simulations with Neal's ideas with real numbers for the dispersions for each 'box', plot the spread, and then send the code to Oleg.

pourshot
06-04-2004, 06:55 AM
I have absolutely NO idea what you just said http://ubbxforums.ubi.com/images/smiley/16x16_smiley-indifferent.gif

But if it fixs the .50cal I will be your friend for life http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif

http://members.optusnet.com.au/~andycarroll68/mybaby.jpeg.JPG
Ride It Like Ya Stole It

Aaron_GT
06-04-2004, 08:50 AM
One thing we are assuming in the code is that the mountings are modelled just as the mountings, and there is no additional dispersion applied as a random factor to account for changes under G load due to wing flex and the like. (In theory you should model the wing flex based on the actual deformation of the wing, but that might be too much to keep track of). I am pretty sure Oleg simplifies just based on gun and mount type, though, from what he has said on here.

PlaneEater
06-04-2004, 03:56 PM
Correct, Aaron. From my understanding of what Oleg has said, the only dispersion that is modeled is of the gun itself. It's a sliding system that starts at single-shot recoil and increases to maximum possible recoil during a sustained burst.

Wing flex, mount vibration, etc, isn't modeled.

BigKahuna_GS
06-04-2004, 06:15 PM
S!

__________________________________________________ ___________________________
WOLFMondo

posted 01-06-04 04:46
This might be considered a dumb/stupid response to this thread or simply not acheivable (so please delete if so) but has no one thought to find examples of these different aircraft that use 0.50's, ask there owners if they can be used in a test, set the guns up as per the instructions and actually fire them as they would have done when calibrating them IRL during the war and record this using whatever methods that are needed to clear this up once and for all?


Wolfgaming.net. Where the Gameplay is teamplay
Posts: 314 | Registered: Fri December 12 2003



PlaneEater

posted 01-06-04 08:52
Mondo: ownership of full automatic .50 caliber weapons is heavily restricted in the US--except for a few collectors and other folks, the only people who have M2s are the military.

Mounting guns on planes is, I believe, illegal except for law enforcement and military duties.
Posts: 240 | Registered: Sun March 23 2003
__________________________________________________ ___________________________


That reminds me of a show on cable TV "American Shooter". The featured guest was a gun expert that owned a several thousand acre ranch in Arizona. Because of this gun experts ties to Hollywood special effect works, he had permits for a Quad 50 mount and an airplane with twin .50cals mounted on it.

He also owned a 20mm multi barrel vulcan type gun mounted on a AA plaform. It shows a night time firing of all weapons with tracers and even a knock down of a small drone aircraft.

In fact it also shows him doing a strafing run with the plane on his property.

Very interesting to watch.


___________________

CCJ: What do you define as the most important things a fighter pilot must know to be successful, relating to air combat maneuvering?

Robert S. Johnson :
It's pretty simple, really. Know the absolute limits of your plane's capabilities.
Know its strengths and weaknesses. Know the strengths and weaknesses of you enemy's fighters. Never fight the way your enemy fights best. Always fight the way you fight best. Never be predictable.

In "Fighter Aces," aviation historians Raymond Tolliver
and Trevor Constable compared Johnson's record with that of two German aces.
Werner Molders was the first ace to score 100 aerial victories and Erich Hartmann is the top scoring ace of all time with 352.

The authors noted that
Johnson "emerges impressively from this comparison." He downed 28 planes in 91 sorties, while Molders took 142 sorties to do the same, and Hartmann, 194.
________


http://www.warplaneswarehouse.com/planes_lg/MS1AOO_LG.jpg

"Angels of Okinawa"

WWMaxGunz
06-04-2004, 11:50 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Aaron_GT:
Ok some quick calcs on a 1GHz machine.

Each figure is the average time for 1
dispersion calculation in seconds to 1 sig fig

Uniform distribution: 3x10e-7
My original code: 9x10e-7
As above, sin, cos as LUTs: 6x10e-7
Neal's single random number code, with uniform random distribution within this: 6x10e-7
Neal's single random number, with just a lot of 'boxes' but no randomness within that: 3x10e-7

So basically with a set pre-cooked x and y dispersions and enough 'boxes' the code will be as fast as what is there now, but model the normal distribution nicely.

At the weekend I'll do some simulations with Neal's ideas with real numbers for the dispersions for each 'box', plot the spread, and then send the code to Oleg.<HR></BLOCKQUOTE>

Just to see if we're on the same path;

The random generates an int that is the index of the LUT slot.
The LUT slot has the dispersion angle.
Since dispersions come out square now, the same LUT array can work for X and Y.
Yeah I know, but it's faster and tighter. http://ubbxforums.ubi.com/images/smiley/16x16_smiley-happy.gif

Aaron;
If you ever have a pile of spare time and want a real kick, check out the Forth
language. AFAIK it may have been the first true OOP. I know that by the 79
standard it certainly was. The thing is that Forth was around long before that.
Charles Moore wrote the core in 1959 to aim telescopes using fast Fourier xforms
(consider computing speeds then, anything fast was about a miracle) as he was an
astronomer. Since then Forth has been used for near everything and yet remains
a virtual unknown. It is used from accounting code to space robots. There are
even microcontrollers available with Forth in the ROM. It's tight and fast. In
1983 I bought a Forth cartridge for my VIC-20 and the whole of Forth-79 plus the
editor fit in 8k! It ran fast and I did, hell I learned OOP on that small of an
environment! Later on that got me work with one benefit, I got to attend pilot
systems training courses to learn what I needed for the coding work. Good days!
Only when C++ came out did I find reason to change languages and that mostly for
the work I got using it. Still, the Forth methods work regardless whenever you
want speed.


Neal

WWMaxGunz
06-05-2004, 12:04 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by PlaneEater:
Correct, Aaron. From my understanding of what Oleg has said, the only dispersion that is modeled is of the gun itself. It's a sliding system that starts at single-shot recoil and increases to maximum possible recoil during a sustained burst.

Wing flex, mount vibration, etc, isn't modeled.<HR></BLOCKQUOTE>

So another runtime step of time on trigger widening the dispersion. Thinking of what
that must do to the M2's... OUCH! But we are asking for lasers?

There are different kinds of modelling.
There is the active kind that is through code and happens at runtime. It slows things
down the more of it is used.

There is also modelling when pre-calculated numbers are made through using factors to
generate them. Those are great but the results need to be checked carefully.

It is possible to use a small amount of runtime code to use a good amount of calculated
results to achieve the most realism for speed, a tradeoff that generally works well.
That is how all flight sims worked back when desktop PC's were running very small bits
of power and memory compared to even low end machines not just now but 4-5 years ago.


Neal

PlaneEater
06-08-2004, 02:08 AM
Any luck with those code segments, folks?

Aaron_GT
06-08-2004, 05:14 PM
Sorry, didn't get chance this past weekend. I hope to this coming weekend.

Tasks are:

1. Write code to use LUT to calculate dispersion (DONE)
2. Find fast normal function for comparasion. I can't really use NAG at work for this, so I'll see what's on my Suse 9 disks.
3. Write program to create dispersions for boxes based on sigma in mils and number of boxes, i.e. contents of the LVTs for 1.
4. Run and time simulations of 1 and 2, and flat distributions to show temporal and statistical performance
5. Port to Visual studio
6. email to Oleg!