War Thunder

Penetration Calculations Done Correctly, And Where Gaijin’s Calculator Fails (Credit to WT Forum User KillaKiwi)

warthunder 1 - Penetration Calculations Done Correctly, And Where Gaijin's Calculator Fails (Credit to WT Forum User KillaKiwi)

Link to calculator:
edit?usp=sharing - Penetration Calculations Done Correctly, And Where Gaijin's Calculator Fails (Credit to WT Forum User KillaKiwi)


What Gaijin's Calculator Does Wrong:

  1. Arbitrary multiplier for a shell being APCBC or not. This shell type did not always have increased pen compared to uncapped AP, APC, or APBC rounds. Rather, it only would yield increased pen if the uncapped round was consistently shattering before, IF the added cap+ballistic windshield kept the round intact upon impact. This looks like a simple, honest mistake on the devs' part, and makes me think they're just too overworked to look at this properly. The fix is to remove this multiplier entirely.
  2. Arbitrary negative multiplier based on HE filler in a shell. HE filler did decrease shell durability, so the devs' reasoning was actually right. However, decreased shell durability does not directly decrease pen. Rather, it decreases the minimum velocity needed for the round to shatter on impact. If the lower limit of shatter velocity is at or near the gun's actual velocity, then it can appear like HE filler is directly decreasing pen. This too looks like a fairly simple misunderstanding from overworked devs that rushed the rollout of the pen formulae. The fix is to simply remove this multiplier entirely.
  3. Shell mass for full-caliber rounds including weight of the soft steel cap and ballistic cap. These irl were too soft to have any meaningful effect on armor penetration. The cap actually acted as a bit more resistance for the main penetrator, often decreasing, not increasing, armor pen in exchange for the round not shattering on impact so frequently. Again, a relatively simple misunderstanding on the devs' part, and a very easy one to fix. While the exact shell masses differ slightly, in general, caps were usually 9% of total APC(BC) shell mass, while ballistic caps were usually 3% of AP(C)BC shell mass. Thus, the mass issue can be dealt with by reducing all APC round masses by 9%, all APBC rounds (flat-nose or not) by 3%, and all APCBC by 12%
  4. The APCR formula they are using being totally wrong, the "original shell mass" (penetrator + weight of APCR carrier metal jacket/APDS sabot) factor being what makes it totally bass-ackwards. Much like caps & ballistic caps, the soft metal carrier jacket (either soft steel or aluminum) just smears out of the way upon impact and has no effect on penetration. Likewise with the discarded sabot casing of APDS which this borked term factors in.
  5. The DeMarre Formula has known flaws when used for tank shells, as it was invented to predict pen on much lower-velocity howitzer rounds shooting cast iron armor plates in the 1890s, not 1930s-50s.
  6. Gaijin's slope modifiers for most round types are pretty bad. AP, APC, APBC, and APCBC are generally underperforming vs slopes. APCR has a mostly correct slope modifier, but as the majority of subcalibers are missing vertical pen, the sloped pen is lower than it should be. APDS has an actually overperforming slope modifier – there are sharp-nose and blunt-nose APDS rounds ingame but they all seem to share the same slope modifier that is halfway too good for sharp-nose rounds and halfway too bad for blunt-nose rounds. Finally, Russian flat-nosed APBC rounds have been overperforming memes for years. This calculator estimates vertical and sloped pen independently of each other, and does not calculate sloped pen as a function of vertical pen.

What needs to change regarding the penetration calculators:

  • Delete unnecessary multipliers, change over to using this calculator. This calculator uses all the same factors that Gaijin's penetration mechanics do for sloped armor pen, but it would be differently coded.
  • Despite significant varieties in shell design across nations and years, the amount of energy needed for a shell to pen armored plate at 60-degree slope is relatively similar. For 75mm and larger shells, most of them require 7.0-7.5 J/mm^2, assuming the plate is equally thick as the gun caliber. What "overmatch" is defined as is actually a reduction in energy needed to pen a plate when shell caliber is significantly larger than plate thickness. These numbers have been measured for enough different shells of different calibers that it can be safely assumed the same for all rounds of similar calibers.
  • Likewise, despite significant differences in shell design across nations, the "ballistic factor" – a number which inversely scales with shell caliber & mass, determining how rapidly a shell loses energy over distance – is more or less the same for every caliber when comparing shells of the same cap type (AP with AP, APC with APC, APCBC with APCBC). This here can be Gaijin's "balancing fudge factor" to use instead of reload rates.
  • For subcaliber rounds specifically, penetrator length/penetrator diameter ratio is also included, which is precisely why modern APFSDS rounds pen so much armor. This is used instead of J/mm^2 to calculate how much armor these round types would pen using actual physics. Gaijin's calculator does not include this when it really should.

Why bother?

Once the pen formulae are updated enough, the ammo issue is settled for all eternity and never needs to be messed with again. Only individual shells might be adjusted slightly. Thus it truly solves a major thorn in the devs' side.


Then both the ordinary players and history buffs are happy. Numbers are close enough to reality to satisfy the latter, and they will force BR decompression to make room for huge restorative buffs to APCR and APDS, which have been gutted over the years.

Source WT Forum Threads where I got my info from, to credit KillaKiwi:

Source: Original link

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