Most relatively experienced players will know, at least conceptually, about the differences between the types of ammunition. AP has 5 degrees of normalization, APCR typically has better shell velocity and 2 degrees of normalization, HE, HEAT and HESH lose no penetration over distance, typically fly a bit slower, and have no shell normalization.
But what does this mean? How does this look in-game? Well, the TL;DR is that in almost all scenarios, the effective penetration AP is greater than APCR and HEAT of the same nominal penetration value. This becomes more significant the higher the penetration value goes.
Armor, in most scenarios, is angled. It allows for lower amounts (and therefore lower weights) of metal to provide more protection. Let’s take a look at the Emil I, a fairly common tank with well-angled turret armor.
Here is the armor model versus the 250mm of HEAT penetration of the SU-152’s stock 152mm gun. At the bottom of the front turret, the bright yellow represents about a 50% chance of penetration, and just below the yellow line at the top of the turret face there’s about a 26% chance of penetration. The red turret sides are single-digit chances of penetration.
But now let’s take a look at the Emil I versus something else:
This is 248mm of APCR penetration, the value of the standard rounds on the Obj. 257 or Tornvagn. At the bottom of the turret the penetration chance is now around 70%, at the top, just below what is now a green line, around a 48% chance, the left turret side ranges from 5-15% and the right turret side from 13-33%.
Finally, let’s take a look at 248mm of AP penetration:
This is the value of the standard rounds on the T34 and the premium rounds of the Skoda T56, and here we see a DRASTIC change. The bottom of the turret is now an 85% chance of penetration, the top location is now a 70% chance of penetration, the left side is from 27-47%, and the right side is from 45-65%.
So what’s the takeaway? Basically, the 268mm of standard APCR pen on your high-tier medium is about equal against angled armor to the 258mm of standard AP pen on that high-tier heavy over there. The 310mm of standard AP penetration on an FV4005 is better than 340 HEAT against a 279e’s upper plate, but worse than 340 HEAT against an E 100’s face. And they’re about equal against an Emil II or Kranvagn’s turret. The Concept 1B may have the same nominal 258mm of pen as the AE Phase I, but since the Concept has APCR, it doesn’t have quite as much penetration as the AE. Furthermore, the 180mm of HE pen on the Caliban is very much inferior than the 190mm of AP pen on the T-44 and Pershing.
It’s impossible to remember exactly how well each shell will do against each armor model. But it’s important to know that when armor is angled, the type of shell can have a massive impact on the chance of penetration. Obviously raw penetration can make up for this. That’s why the 420mm of HEAT pen on the Jageroo is so devastating. And obviously I’m not even touching on penetration loss over distance, overmatch, and ricochet. But this effect is important to hold in the back of your head while playing and comparing penetration values without the actual tanksgg live model in front of you.