Two Calibers?


Skill Star Predator Pt. III




I got so caught up in the wondrous feeling of turning the tables on the TD meta yesterday, I forgot part II of “Skill Star Predator” was actually supposed to be more practically oriented.

I even forgot to mention I found out something important. It’s called the “two calibre rule”. I kept thinking Xeno had gotten it wrong when he started talking about it, because I had never heard of it. I have heard of the three caliber rule, which states that if the calibre of the shell is more than three times the thickness of the armour, it will penetrate regardless of angle.

Here’s what the two caliber rule says:

“…if the armor the shell hits is less than half of the caliber of the shell, normalization is increased by the following formula: basic normalization * 1.4 * shell caliber / nominal armour thickness. If the shell penetrates due to this rule, it moves on to the damage roll. This rule does not apply to HEAT/HE/HESH.”

So, let’s look again at the side of my Object 140. It has a strip of 80 mm armour along the side, that will void the two caliber rule for almost all guns in the game. At 80 degrees, I have almost 500 mm of effective armour out of those 80 mm:


This looks like it would bounce, but it wont because of the two caliber rule


But as soon as the side starts to curve outwards, it’s only 57 mm. The 183 will overmatch that. And let’s see what happens to my 500 mm of effective armour with the two caliber rule:

AP shells normalise at 5 degrees. The two calibre rule says 5 degrees times 1.4 times 183 divided by 80, giving us sixteen degrees of normalisation.

A Jägeru wouldn’t be quite so bad. 17 cm isn’t enough to overmatch the upper curvature, but 5 * 1.4 * 170 is still almost fifteen degrees of normalisation. It’s doubtful you’ll ever have enough effective armour to get a bounce, even at sharp angle.

The way it works out is, if you are angling at an extremely shallow angle, almost zero degrees, it’s like you are already angling out sixteen degrees. Looking at the armour model, that practically means there is no way to angle my Object 140 to get a bounce off the side armour from a skill star, because one of the two rules will negate it all.

The problem with saying that, is the quality of the Information we have to work with. I spoke to Minitelrose about all this, and he explained the several problems involved in making an accurate representation of in-game armour models and penetration mechanics, the way Armour Inspector tries to do.

Basically, Wargaming doesn’t give out any information at all. Everything we know has been assembled by players over a period of several years, and so what we see is the best possible representation, but it isn’t always completely accurate. Trying to keep it accurate is a constant struggle, there’s really no way of knowing if you got it right, and even if you did, everything could change completely tomorrow, and no one would tell you about it.


Which is disheartening, of course. But it also shows us the value of information. The only places I should expect to get a bounce from a skill star is off my severely angled front plate, or the rounded sides of my turret.

There is another lesson to be learned. 183 / 2 is 91.5, meaning if you have 92 mm of armour somewhere – that’s 92 mm of actual armour thickness; not effective armour thickness, you will be safe from both the two and three caliber rules for all guns in the game.

Consider that for your side scrapers. Less than 91 mm means you will sometimes be around 15 degrees further out than you though you were. For 122 mm guns, the number is 62 mm; less than that, and you can add 14 degrees to your side scrape angle.

So yeah. Important knowledge. I should start paying more attention to learning my armour thicknesses on various tanks, and which guns I therefore need to watch out for. For the biggest guns in the game, it’s basically two numbers to remember: 62 and 92. that’s the limit beyond which you only have the regular 5 degree normalisation to deal with from a 122 or a 183 mm shell, respectively.


There is yet another lesson here about how completely bullshXt the skill star is for just negating peoples armour like that, and especially my magnificent Object 140, but I think we all heard that one before. I already knew the skill star is bull. The fact it’s even more bull than I thought it was doesn’t exactly alter my position on it. I just kind of sigh at that.

But learning about the two caliber rule, trying to work out what it means to me in practice, and how I need to alter my gameplay to avoid it; that’s the kind of stuff that makes me sit up and pay attention. I never used to like maths at school, but that’s because I didn’t always see a practical application. I don’t mind it at all now.

There is more to learn. I have a Foch 155, for example. That means less than 77,5 mm of enemy armour, and I will get the extra normalisation. Time to check some of my targets. Oh, and I have a few 130 mm guns as well. That means less than 65 mm, and so on.

This may seem like mere details, and in the grand scheme of things, yes; that’s what it is. But important details. The kind of stuff you need to know, things that should inform your gameplay, just like the overmatch mechanic.

And knowing why you got wrecked may not make you feel any better, although I do sometimes find that to be true. But the point is it will put you in a much better position to learn from your mistakes; they are of course easier to avoid once you know what they were in the first place.


Death to the skill star!


2 thoughts on “Two Calibers?

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