Dual armor ratings

[Ted]

What penetration factor would be needed to for an AP shell to penetrate the front hull of a Pz(t)E 25+25 at, say, zero degrees (instead of the actual 17degrees)?

50? less?

In another words are the dual rating cumulative?

[Redwolf]

In reality less than 50. How much less depends on the nature of the shot.

I do not recall whether that is reflected in CMBB.

[JasonC]

The rule of thumb in the real world for layered plate is that the thickest one counts full, and any others only count about 80%. So 25+25 would resist like 45.

But in CMBB, things aren't that simple, and many vehicles with layer-cake plate are actually modeled as being stronger than the same thickness in one uniform plate. This reflects the opinions of some of their modelers and is idiosyncratic. None of the contemporary armies or designers thought so, and they uparmored to full thickness plates as soon as they could. The layered stuff was merely a quick expedient to make vehicles originally designed far too thin, more survivable.

50mm thickness was meant to deal with Russian 45mm AP (it could not deal with subcaliber 45mm, which was much more common in real life than it is in CMBB, from 1943 on). 20 over 50 was meant to deal with Russian 76mm but was insufficient to do so, and they went to 30 over 50, then 80 uniform, whenever possible. In CMBB, though, 20+50mm front late model Panzer IIIs will bounce 76mm at near as 500 yards. That was more like the danger distance for uniform 80mm plates.

So, in CMBB, it is often a better rule of thumb to reverse the real world formula, and count layered armor as thickest, plus thinnest, plus 20-25% of thinnest.

(This can lead to some howlers, like 30+50mm StuG fronts bouncing 85mm AP at 750 yards, as long as it is 1943 ammo).

Against a Pz 38 with 50mm front, you will need a long 76mm gun. (The overmodeled Russian ampulet flame mortar can also hurt them, though).