primary source 47mm mle1936 wrong ballistic coefficient

CaID · October 26, 2021

# Game version

# Description

the Obus de Rupture de 47 Mle 1936 currently know ingame as the 47mm Mle1936, have the Balistic coefficient of 1.6 while it should have 1.536

# Steps to reproduce the issue

launch the game
check the concerned round

# Additional Information

what is the Ballistic coefficient?

it's a value measuring the speed reduction of the projectile caused by the air-resistance.

in the case of the 47mm mle1936 this value is set to 0.6 while the correct value is 0.536, the difference cause a higher reduction of the speed over the distance, this ingame can be translated by less penetration at longer range. as the ingame performence seem to be a bit off to me, i went to check the coding of the rounds and found the drag value

Spoiler

"bullet": {

"bulletCount": 300,

"mass": 1.726,

"caliber": 0.047,

"Cx": 0.6,

"speed": 855.0,

"maxDistance": 7000.0,

"normalizationPreset": "apbc",

"ricochetPreset": "apbc",

"secondaryShattersPreset": "ap_large_caliber",

"stabilityThreshold": 0.05,

"stabilityCaliberToArmorThreshold": 5.0,

"stabilityReductionAfterRicochet": 0.3,

"stabilityReductionAfterPenetration": 0.0,

"stucking": 0.7, "stuckingAngle": 45.0,

"bulletType": "apcbc_solid_medium_caliber_tank",

"slopeEffectPreset": "apc",

"fresnel": [0.23,0.1,2.0],

"shellAnimation": "video/shells_animations/ap.ivf",

"bulletName": "47mm_mle1936",

"relativeVelHitShift": [300.0,1000.0],

"relativeVelArmorShift": [200.0,1000.0],

"explosionEffect": "hit_39_58mm_metal_ap",

"groundCollisionEffect": "hit_39_58mm_dirt_ap",

"ricochetEffect": "hit_39_58mm_metal_ap",

"waterCollisionEffect": "hit_39_58mm_water",

"explosionPatchRadius": 0.7,

"stabilityRicochetModifier": [

this coding in the spoiler above are the coding that dictate the behaviour of the 47mm mle1936. the drag coefficient is indicated in blue

according to the test reported by the German about the SA37 using the Obus de Rupture de 47 Mle 1936 that was provided by a friend @nxdefiant001 the drag coefficient was then possible to be calculated for every range of 100m and a average for 0 to 2000m, Thanks to @LeGrandSarrazin

Spoiler

M | Yds | M/S | F/S | Calc B Co - Range

0 0 855 2805 1.623 0-100m

100 109 836 2743 1.589 100-200m

200 219 817 2680 1.417 200-300m

300 328 796 2611 1.753 300-400m

400 437 779 2556 1.523 400-500m

500 547 760 2493 1.517 500-600m

600 656 741 2431 1.584 600-700m

700 766 723 2372 1.546 700-800m

800 875 705 2313 1.523 800-900m

900 984 687 2254 1.597 900-1000m

1000 1094 670 2198 1.561 1000-1100m

1100 1203 653 2142 1.568 1100-1200m

1200 1312 636 2087 1.534 1200-1300m

1300 1422 619 2031 1.491 1300-1400m

1400 1531 602 1975 1.599 1400-1500m

1500 1640 586 1923 1.543 1500-1600m

1700 1859 554 1818 1.319 1700-1800m

1800 1969 536 1759 1.637 1800-1900m

1900 2078 522 1713 1.390 1900-2000m

2000 2187 506 1660 1.536 0-2000m

the current Balistic coeficient is a Generic coeficient for APC rounds. this is probably caused by the fact that at first, this rounds was identified as APC and not APCBC as it is now.

the correction of this coefficient would adjust the penetration of the SA47 significantly at greater range but would have a rather small effect at short range.

# Affected vehicles