Gaijin Calculator overhaul

Looking at the speed and weight of the HVAP for the 120 mm T53 in-game, it seems to be loosely based on this.


Although the core weight in-game is 6.8 kg and the mass is 16.3 kg.

Either way it seems to be underperforming in with the calculator if we take these results for granted.
T53 HVAP penetration
15.5 inches at 1000 yards, or 393.7 mm of penetration. Although seemingly there were a bunch of different HVAP rounds tested for the 120 mm, so can’t really say for certain if the one I mentioned above is the one that had this penetration.

From the document Table of Form Factor of Projectiles, the T17E1 may have had a velocity of 4150 fps. If that’s true and the core to carrier weight is about 50%, like it seems to be for US APCR, the chart would look like this.

120mm T53 Ballistics Chart

I’m just going to quote the entirety of The Armored Patrol on the 120 mm HVAP for the T53 cannon, because honestly the T17 HVAP is just too confusing.

T17 HVAP
High velocity armor piercing / composite rigid projectile, taking similar design to the 105 mm T29E3 of the T5E1 gun. Situation Report No. 37 indicated the complete weight between 13.6 – 14.5 kg (4.5 kg tungsten carbide core) with muzzle velocity between 1188 – 1219 m/s. But there is a conflicting sources between each sources, 3 in total.

One is from Situation Report, which is using this specification.
1st Specification:
Weight: 14.51 kg
Muzzle velocity: 1219.2 m/s
Core diameter: (?)
Core mass: 4.5 kg
Core type: Tungsten carbide

Another one is from Detroit Arsenal Automotive Development Conference, indicated an increase to its weight at 16.32 kg (7.25 kg tungsten carbide core) with drastic muzzle velocity drop at 1082 m/s.
2nd Specification:
Weight: 16.32 kg
Muzzle velocity: 1082.04 m/s
Core diameter: (?)
Core mass: 7.2 kg
Core type: Tungsten carbide

T17E1 Mod. 0 HVAP
The last one is from Table of Form Factors of Projectiles, 1958. This shell retained the similar specification from the Situation Report, but went with different designation.
3rd Specification:
Weight: 12.7 kg
Muzzle velocity: 1264.92 m/s
Core diameter: (?)
Core mass: (?) – Probably same as the T17, 4.5 kg
Core type: Tungsten carbide

Yeah, I’ve seen that a few times. Until we can find better information, I’m not sure how much more we can change. I think its pretty safe to say the muzzle velocity is 4150 fps because the Form Factors document was written later than the Detroit document.

Well right now Gaijin seems to have based the HVAP on the Detroit document except the core is too lightweight.

Besides that it has a 63.5 mm core in-game. I don’t really know why 63.5 mm specifically other than the fact that gives 2.5 inches. But that’s also something where there’s just outright not a single source to say which would be the correct value other than speculation.

Yeah, they are definitely using the Detroit document but unless they add core information to the stat cards, we can’t really change it. I don’t think you can use datamined information in bug reports.

You can, or, well, at the very least datamined results have been used for bug reports. It is the case for the transmissions of all the Pershings, the M18s and the M4A3s, which were all changed and corrected in “Drone Age” precisely because of a couple bug reports that used datamined values.

M18s: M18 GMC incorrect transmission - Already Reported & Resolved - War Thunder - Official Forum
M4A3s: 2021-11-30 [2.11.0.92] M4A3(HVSS) incorrect gear ratios - Documented Ground Reports - War Thunder - Official Forum
Pershings: 2021-11-09 [2.11.0.43] M26/T26 series tanks incorrect gear ratios - Documented Ground Reports - War Thunder - Official Forum

Besides, if you do use datamined results… Gaijin can either say that the in-game values aren’t matching the documented values and therefore the bug report is valid, or they say that the documented values are already implemented in the game and the datamined values are inaccurate. Either way it’s a win.

Interesting.

Well, if I can find any core diameter information, I’ll make a report.

Not necessarily true, there is a source for the core diameter of 120mm hvap. But, it doesn’t specify which variant it is, as far as I know. From what I’ve found, the later variants for the T53/T122 had a 15-16lb core. But their carriers would of been based on the later hvap rounds, like 76mm M319 or 90mm M332, which used a lighter designed Aluminum alloy carrier, as opposed to the Aluminum with steel base plate carrier of the earlier rounds. Which means lighter total shell mass, but heavier core.

This is the design used for 76mm M93 or 90mm M304

The Design for the 76mm M319 HVAP Carrier Shell

TM 43-0001-28 M319 HVAP Diagram

The Design for 90mm M332

TM 43-0001-28 M332 HVAP Diagram

All of the larger bore HVAP rounds post 1950 would of used the same carrier shell design as M332, which was originally called HVAP T LT-WT

AD052504 Cover and page with hvap core diameters

AD052504 M48 Armor Distribution Cover

Form Factors Table

76vSk6X

From Ken Estes Book on the M103

T122 Gun from M103

Cut from an Ammunition Data sheet, specific to 120mm guns, 4th column is shell weight

3 Likes

Interesting.

The 48mm core for 90mm really messes up my APCR changes. Not sure how to fix that.

Either 90mm is way low or the 76mm is much higher.

So basically the type of APCR that the current in-game calculator really does not like, sadly. Big heavy core, light hollow carrier.

Also I am embarrassed by how long it took me to realize that the AD052504 source says “120 mm, HVAP” instead of “20 mm HVAP”. It says 2.265 inch core, is it?

2.265 might be the 10lbs core.

120mm T53 Chart Update

If the T17E1 had the 16 lbs core at 4150 fps, it could come close to the 15.5" listed at 1000.

Actually, the document Conraire posted shows 15", which is 381mm, so a close result.

1 Like

Here is some Soviet 85mm data for reference.

The APCR seems high but it roughly matches the 130mm at 1000m listed in Soviet documents.

Shouldn’t the br 365k have a little more penetration at close range compared to the br 365a? I say this because after all the br 365k has a sharp point while the br 365a has a completely flat point.

I had the explosive filler for the K version wrong, so it does get more pen. I’m using the same setup for Soviet APHE because I don’t think Gaijin will want unique equations for multiple round types.

Ah, it’s just that the br 365k and br365a always seemed strange to me, I don’t know which one was made first, what was the use of each one and which one would be used as the main ammunition.

I don’t know much about Soviet ammunition but I believe the sharp AP was first, then the flat AP, then APC was post war.

2 Likes