Yak_Panther Posted June 25, 2021 Posted June 25, 2021 (edited) Problem: 50 cal ap data does not appear to match official data on the round. The bullet penetrates less armor than contemporary tests indicate. The bullet is slower than primary source data seems to indicate. The bullet weighs less than data indicates The drag profile of the bullet appears to be off. This is the in game ballistics table from the Us 50 cal Ap round. Armor=1,840, 22,153, 18,383, 0,613 Armor=100,789, 20,135, 16,338, 0,541 Armor=500,612, 14,81, 11,204, 0,326 Armor=2000,268, 4,16, 3,39, 0,62 Lets look at the first line and see what it's saying about the 50 cal ap rounds performance. Armor=1,840, 22,153, 18,383, 0,613 What this is saying is, At range 1 this round will be moving 840 mps, It will penetrate 22 mm of armor and do 153 damage. The first pair represents the maximum amount of armor penetration at that range. The amount of damage increases as the armor thickness decreases. EG in the second pair, If the round impacts 18 mm or less of armor it will do 383 damage. The damage increases up to 613 when there is no armor. So does this ballistics table match reality? Let's look at some source material and compare. https://apps.dtic.mil/sti/pdfs/ADA953652.pdf First is a chart From Watertown Arsenal circa 1942. It gives us test data on penetration capabilities of the round against RHA of varying thickness and various Brinell Hardness. Based on two penetration criteria, The Army and Navy limits. The difference in the definition of Complete Penetration, accounts for difference in velocities in the table. Back to Il 2 table table Armor=1,840, 22,153, Armor=100,789, 20,135, Armor=500,612, 14,81, // calculated based on the reference point for armor penetration for a given bullet 375m-16mm Armor=2000,268, 4,16, 375m = 1230.3 ft 16mm = 0.629921 inches ~ 10/16’ths inches Comparing the game to the hardest plate tested at the Navy limit . At ~2700 fps the game’s penetration values is 3mm less than Watertown test. Pretty close match. However there is a discrepancy between the penetration capability as the velocity decreases. The games requires more velocity to penetrate than the Watertown tests seem to indicate. The game has a velocity limit for 14 mm of armor (~.5 inches) at 612 mps. Watertown has the required velocity to penetrate .5 inches of armor as 1660 fps or 505 mps. The game requires 20% more velocity to penetrate the same amount of armor as the Watertown tests. Let’s look at some other primary source data. This is from Terminal Ballistics Data Part 2. https://cgsc.contentdm.oclc.org/digital/collection/p4013coll8/id/2374 The Chart gives us a way to find the penetration capability of the round, at various ranges, velocities and target angles. I’ve Plotted the velocity and ranges from against this ballistic table for the 50 cal AP m2 round. The Il 2’s round is substantially slower and does less penetration than the chart predicts. Here are the Watertown tests results plotted in a similar manner. We can overly the Data from the game and the Watertown test's to see how well the match up to the chart. It looks like the game data maybe based on a plate at 20 degrees. Since the game data provides both range and speed we also create a chart to predict the velocity required to penetrate any thickness. The Game seems to under estimate the penetration capabilities of the round until the range exceeds 1000 yard, then slightly over estimate them. The Il2 .50 cal AP round is probably too slow. The Velocity Problem: There also appears to be discrepancy with the velocity. From Fighter Fun Harmonization AAF Manual 200-1 As a Table and converted to metric. Range Ft TOF V/t (FPS) Range M V mps 200 0.07 2857.142857 60.9570253 870.8146471 400 0.15 2500 121.9140506 761.9628162 600 0.23 2500 182.8710759 761.9628162 800 0.31 2500 243.8281012 761.9628162 1000 0.4 2222.222222 304.7851265 677.3002811 1200 0.49 2222.222222 365.7421518 677.3002811 1400 0.58 2222.222222 426.6991771 677.3002811 1600 0.67 2222.222222 487.6562024 677.3002811 1800 0.77 2000 548.6132277 609.570253 2000 0.87 2000 609.570253 609.570253 2200 0.98 1818.181818 670.5272783 554.1547754 2400 1.09 1818.181818 731.4843036 554.1547754 2600 1.2 1818.181818 792.4413289 554.1547754 2800 1.32 1666.666667 853.3983542 507.9752108 3000 1.44 1666.666667 914.3553795 507.9752108 The Game puts the velocity at 500m as 612 mps. The table it’s closer to 677mps. Which wouldn’t matter that much if the Penetration to velocity was more closely match to the data. So what could be wrong. Well the drag coefficient is wrong, so is the mass. The bullet mass is low in game In game its .0419 Kg Fighter Fun Harmonization AAF Manual 200-1 lists it as To .1015 lb or .046 Kg https://apps.dtic.mil/sti/pdfs/AD0800469.pdf Gives the weight as 710 grains = 0.0460072 Kg So 6 grams less. Therefore less kinetic energy for a given velocity. As Ke = .5 mv^2 The Drag coefficient appears to be off as well. Here’s it’s presented in the older Kd format. It can be converted to more prevalent coefficient of drag as Cd = 8pi*Kd This report list ~.160 and .115 as the Kd. Converting to CD Cd =8pi*.160 Cd = 25.13 * .160 Cd =.4 A Cd of .4 tracks well with ballistically similar rounds. https://apps.dtic.mil/dtic/tr/fulltext/u2/a219106.pdf M8 Ball Ammo Cd From: https://apps.dtic.mil/sti/pdfs/ADA289645.pdf The Game has the base Cd as .45 so it’s close. However the reset of implementation results in it being to draggy. Per the 50 cal AP game data. Mkr = 0.97 // the value of the Mach number, after which the increase in Cx begins until the moment M = 1, depends on the shape of the body but not on the size Mmax = 2.0 // the value of the Mach number, to which the decrease in Cx, which began at M = 1, is completed, depends on the shape of the body but not on the size Cx_0 = 0.16 // the value of the resistance value at (M <= Mkr), depends on the shape of the body but not on the size Cx_max = 0.45 // value of the set of resistance at (M = 1), depends on the shape of the body but not on the size Cx_1 = 0.32 // value of the resistance at (M> = Mmax), depends on the shape of the body but not on the size And the the Drag Chart Mkr = 0.97 // the value of the Mach number, after which the increase in Cx begins until the moment M = 1, The critical Mach number, Looks about right Mmax = 2.0 is to high, this should be 1.2. Mach Cx_0 = 0.16 // the value of the resistance value at (M <= Mkr), The CD below the critical Mach., Seems a little high compared to the other rounds, they are close to .12 Cx_max = 0.45 // value of the set of resistance at (M = 1), depends on the shape of the body but not on the size, Very close to the chart. Cx_1 = 0.32 // value of the resistance at (M> = Mmax), Drag above Mach 2. The result is that the bullet spends to much time in high drag area. This is probably why the velocity seems low compared to primary source data. The reported Ballistic coefficient of the M2 AP is ~ Where the Ballistic coefficent = Mass / Cd * Cross sectional Area, Front .458 From https://cgsc.contentdm.oclc.org/digital/collection/p4013coll8/id/2374 From a wartime report about the Ballistic coefficients of production rounds. https://apps.dtic.mil/dtic/tr/fulltext/u2/491936.pdf The reported Bc could be used to determine a new velocity to range table. Then spline between the Watertown test and the predicted penetration as the Dev's feel is necessary to determine the penetration capabilities. Edited June 25, 2021 by Yak_Panther clarity 3 1 1 17
Yak_Panther Posted July 6, 2021 Author Posted July 6, 2021 (edited) Historic 50 Cal Ap I’ve conducted more research and now feel I have created a more historically accurate representation of the 50 cal m2 ap round. I’m attaching the files as zipped folder, that’s compatible with mod managers. These changes do not attempt to balance the round in terms of game play. I’ve simply updated the 50 cal ap shell file, to reflect the data in historical documents. The changes are as follows. The range penetration table has been updated. The damage values have been updated in accordance with the game standards. The muzzle velocity has been updated for the 36 inch aircraft MG. The drag has been reduced, The mach where peak drag occurs has been reduced. The mass of the round has been increased. All the changes are based on primary source data for the round. The primary source materials for my mod are. “Terminal ballistics data, volume III, bombs, artillery, mortar fire & rockets.” Office of the chief of Ordnance, https://cgsc.contentdm.oclc.org/digital/collection/p4013coll8/id/2374 “Report 710 / 466, An Analysis of Firing of Cal. 50 AP Ammunition Against Homogeneous Armor Plate” Zener, Watertown Arsenal 1942 https://apps.dtic.mil/sti/pdfs/ADA953652.pdf “Report 620, Aerodynamic Data for Spinning Projectiles” H.P. Hitchcock Ballistic Research Laboratories, Aberdeen Maryland 1947. https://apps.dtic.mil/sti/pdfs/AD0800469.pdf “Report 478, Ballistic Coefficients of Small Arms Bullets Of Current Production”, Karpov, Ballistic Research Laboratories, Aberdeen Maryland 1944 https://apps.dtic.mil/dtic/tr/fulltext/u2/491936.pdf “The Erosion of Guns Part Two: The Characteristics of Gun Erosion.” Burlew, National Defense Research Committee. 1942 https://apps.dtic.mil/sti/pdfs/ADB280242.pdf “AAF Manual 200-1, Fighter Gun Harmonization”, Headquarters Army Air Forces, Washington DC 1945. https://www.avialogs.com/trainingmanuals/army-air-forces/item/56042-aaf-200-1-manual-for-fighter-gun-harmonization “War Department Technical Manual TM 9-225. Browning Machine Gun Caliber .50 AN-M2, Aircraft Basic” War Department, Washington D.C. 1947. http://www.nj7p.org/Manuals/PDFs/Military/TM%209-225%2028-Jan-47%20Google.pdf “TM 9 1907 Ballistic Data Performance Of Ammunition” War Department, Washington D.C. 1948 https://archive.org/details/TM91907BalisticDataPreformaceOfAmmunition “Discrepancies Associated With The Drag Characteristics of Primary Fragments”, Tatom, 2010 https://apps.dtic.mil/sti/pdfs/ADA532300.pdf “The Aerodynamic Characteristics of .50 Ball, m33, API, M8 and APIT, M20 Ammuntion”, McCoy, Ballistic Research Laboratory, Aberdeen, Maryland 1990 https://apps.dtic.mil/dtic/tr/fulltext/u2/a219106.pdf l’ll explain my changes below. The mass of the round has been increased. The game currently has the mass of the shell at .0419 kg. This is too low. We have 3 separate figures for the mass of the round. They vary from 710 grains to 708 grains. BRL report 478, notes that the core of the round was changed in 1943 resulting in a reduction of the weight of the round.The Air Force uses a weight of .1015 lbs or 710.5 grains. The Ordnance Department goes with a weight of 708, Hitchcock in BRL 620 notes the sampled round is 709 grains. We’ll error conservatively and settle on a weight of 708 grains .0458kg The muzzle velocity has been updated for the 36 inch aircraft MG. The Game has the muzzle velocity set to 840 mps (2755.91 fps). The Air Force manual 200-100, gives the muzzle velocity of the AP round as 822.96 mps (2700 feet per second). Across multiple sources, the Department of Ordencance reports the muzzle velocity of the 36 inch barrel AN/M2 is 865.63mps (2840 fps). This is from the 50 cal AN/M2 aircraft machine gun manual issued by The Ordinance Department. http://www.nj7p.org/Manuals/PDFs/Military/TM%209-225%2028-Jan-47%20Google.pdf The muzzle velocity is also listed as 2840 FPS,in “Terminal ballistics data, volume III, bombs, artillery, mortar fire & rockets.” and “TM 9 1907 Ballistic Data Performance Of Ammunition”. “The Erosion of Guns, Part Two: The Characteristics of Gun Erosion” quotes the velocity as 2800. So why did the Army Airforce list the velocity as 2700 in their manuals? “The Erosion of Guns Part Two: The Characteristics of Gun Erosion” gives us the answer. Thus, half way through its service life, the gun would be expected to shoot at 2700 fps, due to erosion of the barrel and other parts. The Air Force is likely calibrating their sights, harmonization patterns and ballistic tables based on the performance of a well worn 50 cal, half way through it’s service life. Therefore I’ve set the muzzle velocity to 864 mps. My justification is that this resembles a new gun and therefore follows the game’s precedent of simulating new / factory fresh specifications. I believe this to be in good faith, as none of the weapons seem to have their muzzle velocity lowered to their expected half life levels. Changes to the Ballistic Table, Penetration and Damage. The Watertown Arsenal Penetration tests, Report 710, are within .02 inches of The Ordnance Department's calculated penetration results presented in “Terminal ballistics data, volume III, bombs, artillery, mortar fire & rockets.” and “TM 9 1907 Ballistic Data Performance Of Ammunition”. Therefore I have based the penetration table on The Ordnance Department’s charts. The damage stats of the guns in game are calculated by comparing the kinetic energy of a round to that of the German 20mm AP round at 100m. The German 20mm does 1000 damage to an unarmored target at this range. The formula to compute the damage of the 50 cal at a range of 100 meters works out to: Damage = (KE 50 cal / KE German 20mm) * 1000 Where KE = .5* Mass*(V^2) The German 20mm has a mass of .0117 kg and at 100m has a velocity of 642mps. The German 20mm has a KE of 24.11 Kilo-joules at 100 meters. The 50 cal AP, traveling at 821 mps with a mass of .0458 has a KE of 15.43 kj. The damage of the 50 cal at 100 meters is (15.43/24.11)*1000 = 639.9, I’ve rounded up to 640. The damage decreases due to range and armor follows the same scale as the original 50 cal rounds. Changes to Velocity and Drag. The Drag coefficient was changed from .45 to .4. The Velocity where maxim drag occurs was lowered. The Velocity of the round at 1, 100, 500 and 2000 meters has been changed. The current drag coefficient of the round .45 more closely resembles the G5 ballistic coefficient. A G5 ballistic coefficient is not the same as the coefficient of drag, Cd / Cx. Where Cd = 2*Force of Drag / Density*Velocity^2*area. The G5 ballistic coefficient is a way of relating how much drag a given bullet has compared to a reference model. The two drag notations cannot be used interchangeably to compute a ballistic profile for a bullet. However, the G5 drag profile can be used to compute a ballistic table based on the Siacci Method. This was how ballistic profiles were calculated to about the 1950’s when computational methods became available. The range velocity table implemented in the mod is based on the Sicacci Method. The table is based on a muzzle velocity of 863.9mps, a projectile weighing .0458kg with a G5 ballistic coefficient of .458. Resulting in the following range to velocity table Range Velocity 1 839.9 100 821 500 660 2000 295 The G5 profile of .458 is based on data from “Terminal ballistics data, volume III, bombs, artillery, mortar fire & rockets.” And, “Report 478, Ballistic Coefficients of Small Arms Bullets Of Current Production”. This document, provides a computed G5 ballistic coefficient based on firing a round between two sensors. The report states that C5 and G5 functions are numerically indistinguishable. Therefore using a G5 ballistic coefficient of .458 is a valid approach to creating a new ballistic table utilizing the Sicacci Method. Changes to Cx, coefficient of drag. Since the Ballistic Coefficient is not the coefficient of drag, Cx was changed to .4 Hitchcock does provide us with a drag chart in “Report 620, Aerodynamic Data for Spinning Projectiles”. However, the notion at the time was KD which is different from Cd / Cx the game uses. Hitchcock’s KD = (4/Pi) Force *Drag / *air density* bullet diameter^2 Velocity^2. So we have to convert it to Cd /Cx. McCoy gives the conversion factor as Cd/ Cx= (8/pi) * Kd In “The Aerodynamic Characteristics of .50 Ball…” The methodology is also backed by Tatom in “Discrepancies Associated With The Drag Characteristics of Primary Fragments”, Using the data in Hitchcocks chart and converting it to Cd / Cx Or Cx =.162* (8/pi) Cx = .41 Hitchcock’s drag table tells us that the Peak drag occurs at ~ 1.2 mach. Therefore Mmax=1.2 These results validate with McCoy’s 1990 testing of ballistically similar rounds. Therefore I’m comfortable with these parameters. I believe this implementation of the 50 cal AP round to be historically accurate and inline with methodology used by the developers. I’ve tried to keep from having to interpret or guess by a heavy reliance on primary sources. The changes to bullet_usa_12-7x99_ap.txt ////// PhysicsBody properties VisualImage=0,"graphics/ammo/ammoRmg.mgm",false visualradius=4 SoundScript="" ImageAttrs="IA_NOMINPIXELS","IA_NOROTINTERPOLATION","IA_NOCLIP" //CollisionBody="graphics/ammo/ammo.col" NoDirecion=true NoCollision=true // дальность, скорость на этой дальности (на 0м - указать на 5км/ч меньше расчетной), пары броня-урон за броней. Броню больше, чем в первой паре, не пробьет // за базовый взят урон на дальности 100м при нулевой броне, на макс. броне урон равне 0.25 от базового, на 0.8 макс. брони урон равен 0.5 от базового // урон при нулевой броне уменьшается с дальностью по соотношению квадрата скоростей // скорости по дальностям взяты из лога утилиты расчета .bin файлов пули (расчет таблиц наведения), на 10км/ч меньше ресчетной // т.к. если скорость окажется больше расчетной на данной дальности, то дамага не будет // базовый урон расчитан по соотношению кинетических энергий на дальности 100м между данной пулей и референсной пулей SHELL_GER_20x82_AP (=1000) Armor=1,863.9, 28.9,249, 18,479, 0,708 Armor=100,821, 24.8,234, 16,437, 0,640 Armor=500,660, 17.7,169, 11,291, 0,414 Armor=2000,295, 6,142, 3,165, 0,188 // аэродинамические коэфициенты подобраны исходя из совпадения графика скорости по дальности для эталонной пули (посчитано на балл. калькуляторе) Gage=12.7 //калибр DefaultStartSpeed=864 //дефолтная начальная скорость при стрельбе из простых пушек (наземка) MaxDistance=2500 //предельная дальность, дальше которой объект удалится Mass=0.0458 //масса пули Mkr=0.97 //значение числа Маха, после которого начинается повышение Cx до момента M=1, зависит от формы тела но не от размера Mmax=1.2 //значение числа Маха, до которого завершается понижение Cx, начавшееся при M=1, зависит от формы тела но не от размера Cx_0=0.16 //значение к-та сопротивления при (M <= Mkr), зависит от формы тела но не от размера Cx_max=0.4 //значение к-та сопротивления при (M = 1), зависит от формы тела но не от размера Cx_1=0.32 //значение к-та сопротивления при (M >= Mmax), зависит от формы тела но не от размера R=0.006475 //радиус пули LiveTime=7.0 //время жизни объекта (большее из двух: время полета на MaxDistance или время горения трассера + 3.5с) TimeToDestroy=0 //время жизни объекта после попадания в скрытом состоянии, что бы трейл трассера не пропадал пока не расствориться TracertShowtime = 3.63 //время горения трассера MaxRedirections = 2 //максимальное кол-во рикошетов RedirectedLifeTime = 1.5 //время жизни после первого рикошета DestroyOnExplosion=false //используется только для бронебойных пуль (default =true) с целью обеспечить применение Hit..Effect вместо Hit.., при сохранении пробоя препятствия на вылет //что в свою очередь требуется для "прицепления" эффектов попадания по движущейся технике, а так же гарантированной передаче попаданий в сетевой игре BeamStopDistance = 0.10 //порог расстояния, проходимого пулей после первого попадания в конвекс с "^", свыше которого будет устанавливаться декаль "пробития" NetworkDecals=true //true - декали попаданий будут передаваться через сеть и отображаться на фантомах debug=false DefaultBulletSpeed = 864.0 //дефолтная начальная скорость при стрельбе из комплексной (авиационной) пушки неопределенной модели BulletSpeed = "M2.50", 864.0 //начальная скорость при стрельбе из комплексного (авиационного) пулмета УБ BulletSpeed = "M2.50 45in", 895.0 //начальная скорость при стрельбе из комплексного (авиационного) пулмета УБ Historic 50 Cal AP.zip Edited July 7, 2021 by Yak_Panther spelling 3 9 10
Denum Posted July 19, 2021 Posted July 19, 2021 Lovely mod! You don't feel like you're shooting marshmallows! So much data too. Kinda looks like you've already done the majority of the research and heavy lifting... I'd hope this gets applied as a temp fix. 6
354thFG_Drewm3i-VR Posted July 19, 2021 Posted July 19, 2021 (edited) 2 hours ago, Denum said: Lovely mod! You don't feel like you're shooting marshmallows! So much data too. Kinda looks like you've already done the majority of the research and heavy lifting... I'd hope this gets applied as a temp fix. I would love to see this as a temp fix too. This with the box convergence fix helps so much. Edited July 19, 2021 by =AW=drewm3i-VR 1
354thFG_Panda_ Posted July 19, 2021 Posted July 19, 2021 Shouldn't this be posted in the armament and equipment thread?
354thFG_Drewm3i-VR Posted July 19, 2021 Posted July 19, 2021 1 hour ago, LR.theRedPanda said: Shouldn't this be posted in the armament and equipment thread? Yes, good idea since it is a clear data value and ballistics error with data to back it up. What say you @Yak_Panther?
Denum Posted August 6, 2021 Posted August 6, 2021 (edited) Hello @Han @-DED-Rapidus @Jason_Williams Please forgive me for the tags. I had seen there was some concern that this wouldn't be sufficient as a fix. I can't speak for everyone, but within the groups I frequent, most players felt this was an acceptable fix for the time being until/if the damage model can be revised later on. To my understanding it only changed the .50 weapons on allied aircraft? Is implementing these changes possible? Yak has presented a ton of data that seemed to line up with his suggested changes. Just seeking some clarification on it, if you have the time. As always. Thank you for the hard work. I hope everyone has a pleasant weekend. Edited August 6, 2021 by Denum 5
354thFG_Drewm3i-VR Posted August 11, 2021 Posted August 11, 2021 New update is out, glad to see the .50s were hotfixed! Oh wait... 1
354thFG_Drewm3i-VR Posted August 15, 2021 Posted August 15, 2021 1 hour ago, Denum said: Coming up on two weeks, not a single word. The data has been presented. A test file has even been made. Nothing. Guys I'll be frank here. This feels like a great big middle finger to alot of people. Time could be found to turn HE shells into miniature nukes with the fuel tank changes? Time could be found to adjust Axis AI cannon shells? ?
Jason_Williams Posted September 3, 2021 Posted September 3, 2021 1. We don't have time to study this data at the moment. 2. When we plan to tweak such things we will let you know. Accusing us of ignoring you or "giving you the middle finger" just because we can't address this issue right now, OR we simply disagree with what is presented just shows us how impolite and rude some of our customers can be. Closed. We'll review this when we have time and are going to work on these items. Jason 3 6 1 2 6
1CGS Han Posted September 5, 2021 1CGS Posted September 5, 2021 Hello everyone. 1. These tables in bullet config do not affect too much on bullet's damage against airframe - while airframe is made from non armoured parts any AP bullet penetrates it's parts without significant resistance. So for AP damage against the airframe and skin the bullet diameter and holes quantity is the main criteria. But these parameters are affecting how the bullet penetrates trough airplane. So with less mass bullet can be stopper by massive parts or luqid volumes earlier. Also they may affect how much damage the engine, or radiator, or other "device" will receive. And offcourse they affect how bullet penetrates armoured plates. 2. This table is not determining which speed on which distance the bullet have. This relation in this table is draft and used by AI in some cases to realize - is there a matter to fire at armoured target at some distance or not. Real buillet speed in game depends on may things - plane velocity, specific gun muzzle speed (depending on overheat also), altitude, muzzle elevation, some other things. Bullets flying not "by table" but by intergation of aerodynamic, mass and obstacle resistance forces with taking in count many "start parameters" lsited in previous sentence. So reverse-engineering of bullet ballistics you do using this table in config - is not the way to realize bullet flight parameters in different circumstances in the game. 2. We can't say where these 41.9 gramms and 840 m/s are coming from - looks like wrong reference was used in 2015 when we have developed the P-40E. 3. We will change mass and muzzle velocity for .50 bullets in game in the next update (correlation between updated source and updated .50 in-game ballistics is on the attached graph). 4. This change will affect a bit of ground target strafing and some plane devices damage, but not airframe and skin damage. 5. A new big approach for common level of projectiles damage on airframe, skin and devices in upcoming later. 9 17 6
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