Thanks to Babykim, EU
Some explanations about the penetration mechanic in relationship to the changes for German guns by developer BadPreacher.
Source: https://forum.worldo…comment-3578275
Let us start with HE. The penetration is computed according to the 1/6 or 1/4 caliber rules, rounding to the nearest whole number. The resulting number is the armor thickness that the HE shell cannot penetrate. For example, for a 152mm HE shell we get approximately 25.334 (152/6), which rounds to 25, meaning that 25mm will not be penetrated, but 24mm or thinner will be.
The 1/4 rule in 0.6.6 for German guns applies as follows:
1. Main battery: all battleships and cruisers of tiers 4-10,
2. Secondaries of 128mm and 150mm caliber: all battleships of tiers 7-10, and cruisers Roon and Graf Spee.
Turning to the AP. The penetration is computed according to the 14.3 rule, without rounding. Divide the gun caliber by 14.3. A bounce cannot occur if the result exceeds the thickness of the armor. The check for penetration accounts for the impact angle (normalization), so that the normalized line-of-sight thickness* of amour applies. Consequently, even if the shell did not bounce it may fail to penetrate the armor.
*) Quote Wikipedia: For example, armour sloped sixty degrees back from the vertical presents to a projectile travelling horizontally a line-of-sight thickness twice the armour’s normal thickness.
