It seems that precisely because of that material change flat penetration is sacrificed in order to achieve higher slope penetration. However, to what degree that sacrifice is I don’t have a clue.
Edit: Here’s the information from the old forum page that talked about these changes.
Unlike the hard alloys, penetrators made of heavy tungsten alloys (HTA) lose mass and significantly change their geometry when passing through an armor, while a kind of influx is formed on the nose of the penetrator, which significantly increases the collision area.
Due to the washout of the core material and a larger collision area, and other things being equal, tungsten alloy penetrators have a significantly lower penetration ability when firing at the barrier at acute angles, however, when interacting with obstacles at larger angles, the opposite trend is observed. Because of the plastic deformation during penetration, HTA penetrators change their trajectory much less than hard-alloy penetrators, and this quality becomes useful at large angles of impact with the obstacle.
Some of it is to challenge some of the notions people have about APCR/HVAP, and APDS sloped penetration performance. Especially on the Ogival core versions. The Ogival core APDS is essentially a glorified HVAP projectile, that retains velocity better due to reduced drag from having less cross-section and better aerodynamics. Which would make it appear to have better high obliquity performance at range.
The current performance of L52/M728 I believe is due to a report in the past from a Soviet document, where they tested western APDS rounds captured from one of the Israeli conflicts. The problem with the source is, from what I can tell, they used the same standards of penetration for both types of cores, which wouldn’t necessarily produce proper results. The reason the US uses protection criterion with Tungsten alloy cored projectiles, is because they erode during penetration. If they were using criteria that required a certain portion of the projectile mass to pass through the plate to be considered a “complete penetration” then the Tungsten alloy core would appear to penetrate less at low obliquity due to losing mass to erosion during penetration.
I don’t quite understand how this correlates to it having better slope performance.
Also this is probably the simplest, yet most mind blowing explanation that makes complete perfect sense. Because I remember seeing that source, and stuff like M392 seemed to have performance that correlated to other sources, but then M728 just seemed way off.
I had to remember how to use the graph myself. As there are two ways to do so. One way is choosing a velocity, and then seeing what plate thickness range a given core could penetrate 5% chance on the high end, 95% chance on the low end. And the other way is to select a plate thickness and a given core, and then use the graph to determine what the ballistic limit velocity range would be.
However, it’ll be easier for me to show with lines and such on an example image, than it would be to explain, which will take some time to prepare.
Yeah I’m not sure how L52 could penetrate so poorly in flat penetration. L15 suffers it too and Chieftain is not a tank that needs more suffering.
Also I know this is almost completely unrelated but I’m super suspicious of all T-54/T-55/Type 59s new 8 rounds per minute fire rate which is identical to M48 and Chieftains.
The documentation of the L11 guns acceptance said 10 AIMED rounds a minute was achievable, whereas the British T-55 tests from around the same time gave a static T-55 an aimed rate of fire of 1.9 rounds per minute. I mean different tests sure so different standards but gives some idea of the difference, because it’s not just “this is what it’s rate of fire was in this test” it’s “we were baffled by this slow rate of fire”. At a time when Chieftain was in service.
So there’s absolutely no justification for it IMO, T-55 is using the extreme upper bound of reasonable fire rate while Chieftain and M48 especially use a lower bound. And IK it’s a game Balance etc, but these T-54 49 went from 7.3 to 8.0 because of this change! It’s also makes the game blander when 3 equivalent cold war tanks now have identical rates of fire, when there’s very little justification for that.
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.
