In this method:
1: You choose a velocity at which you want to figure out about how thick a plate the round can penetrate at that velocity.
2: Then you pick the round.
3: You trace a line from the velocity point, through the core caliber density point of the round, to the first vertical y-axis line on the main part of the graph.
4: Then you trace a horizontal line from the point where the first line meets the graph’s first y-axis line, across the probability band for the angle you’re trying to figure out. In this example, I’m looking at vertical or 0-degree penetration.
5:Trace vertical lines down from the points where the horizontal line intersects the inner and outer edges of the shaded area to the x-axis line labeled e/d, this is the plate thickness to core diameter ratio range.
6: Trace lines from the e/d intersect points, across the core diameter point for M93, to the lower line labeled plate thickness inches. The resultant thicknesses are a 5% chance to penetrate the higher thickness, and a 95% chance to penetrate the lower thickness. As the document states, there’s a 90% probability spread.
So for M93, at 3200 ft/s or 975 m/s, V5 would be 8(2/8) inches or 209.55 mm and V95 would be 7(1/8) inches or 180.975 mm, giving a V50 of ~195 mm.
Even though that’s ~50 m/s lower than what it does from the muzzle it’s still higher than what it does in-game… After checking TBDV3, M93 reaches 3200 ft/s at roughly 340 yards, or roughly 310 meters.
Edit: I tried 3400 ft/s for M93, which is 1036 m/s, and ended up with a V5 that was out of the graph but seems it would line up exactly with 9(1/8) inches or 231.775 mm, and a V95 of 7(6/8) inches or 231.775 mm, so V50 would be 214~ mm. 3400 ft/s is M93’s muzzle velocity if I’m not mistaken.
I assume you’ve seen these tables before, from that Terminal Ballistic data volume III thing (and how to read them hah). Though the more extreme angles are just estimates it’s clearly underperforming in game at 0 and 30 degrees, I wonder why this has never been fixed? Possibly because when they added Germany, USSR, USA they dolled APCR out to nearly every single tank and making it work properly might completely flip ground meta on it’s head, especially if it was doubled with making APHE more realistic.
I know 105mm T29 APCR off this British sourced exert is estimated to get 15 inches normal point blank and 11.3 at 30 degrees, but in game it gets 11.46 inches and 8.5in respectively. It gets even worse beyond that, it’s estimated penetrate 7.6 inches at 45 degrees doesn’t work in game, (i used TigerIIH 7.35inch turret front as reference) and it couldn’t penetrate until 31 degrees! Meaning that round significantly suffers in game.
I have TBDV3 as a PDF on my computer and do know how to obtain the results.
However, what I’ve read from @MiseryIndex556 and some others is that the tables on TBDV3 for M93 and M304 HVAP rounds were obtained using tests on softer armor, so the values are a bit inflated.
Still, even with that in mind US APCR in general does just underperform, and really the calculator is to blame.
As an example, let’s look at 1249 m/s M332 and the long 90 mm T44 APCR, fired at 1143 m/s. That is a 100 m/s increase for M332, yet in-game it has lower flat penetration at close range, despite the fact that it uses the exact same core as T44 (both projectiles use a 3.6 kg, 47.6 mm diameter tungsten carbide core).
Edit: I forgot to mention that 90 mm APCR rounds have a 38.1 mm core instead of the correct 47.6 mm, which means that they actually have a higher penetration value from the calculator than they should…
In game performance screenshots
This just shows that the calculator is just… messed up to say the least.
I thought I’d also throw these in as examples of the current tungsten carbide layer issue. As it seems a planned change very poorly implemented and not really explained to the community at all as far as I’m aware.
90mm T44 shot hugely affected by multiple layers of armour.
M304, M332 and T44 all have 3.6 kg, 38.1 mm diameter cores.
The calculator simply punishes APCR rounds that have lighter carriers and heavier cores. The later US APCR rounds like M332 and M319 for the 76 mm are precisely this, having cores that make up over half of the weight of the entire projectile precisely because the carrier is as light as possible.
T137 is an APDS round. It’s the same sub projectile as the T279 used by the T54E1 but the T54E1 fires it at 5100 fps, while the 90mm T137 is fired at 4100 fps.
2C7 is quite interesting, is there more to it? It mentions at the bottom Fk 96 Field Gun, but it isnt listed above.
Also under 105 mm there are 2x K 18 and 2x L FH 18 each with a low velocity, however they seem to be typos/generalisation (considdering that they included the number 18 at the bottom translation), the K 16 and LeFH 16. The velocity of the LeFH 16 is 390m/s for the weightclass of the Pzgr Rot Apcbc, while of the LeFH 18 it is 470m/s.
I mean, calling the S.Pz.B 41 an Heavy Anti Tank Gun is also incorrect, heavy anti tank RIFLE would be more fitting. They also included the year dates as type designation FK 96 as field gun, K 18 as medium gun, LeFH 18 as light field howitzer, while there were multiple different guns of different years.
The problem with armor penetration against sloped armor is that it becomes harder to know if the penetration against 0º in game is correct or not.
Sure, in game Pzgr.40/43 has 206 mm of 30º penetration at point blank instead of roughly 245 mm that your documents show, however that could be due to simply the universal slope modifiers that Gaijin uses for APCR not fitting Pzgr.40/43, rather than the actual flat penetration being wrong, which is what actually calculated.
The data from TBDv3 appears to be normalized to 220bhn plate for HVAP rounds. The values from the 2C6 graph follow natural plate hardness to thickness value changes. As in the thicker the plate, the softer the plate to a low point of 220bhn.
I downloaded the google sheets calculator that @Peasant_wb made from the 2C6 data a while back, and have been looking at that and testing the bhn settings. Though his is converted to use metric values for mass and diameter, and output for limit velocity. I also have one that Godman made for me, but I can’t quite figure out what part of the equation or table he used to set the bhn to a certain value.
I’m probably going to be doing some modeling in fusion 360 today, as I need to model 88mm pzgr40 so I can figure out the density of the tungsten carbide used in the core. Then I can use that to get the mass of the 75mm pzgr 40/42 core that I’ve already got modeled. I need to do the same for a Soviet apcr round as well to get the density for their tungsten carbide.
Yeah, I think you’re right about TBV3 being normalized to 220 BHN. AD301343 shows M93 penning 8” 220 plate at 2975 fps. DeMarre that to 3400 fps gives you 245mm, roughly the 9.6” from TBV3.
