10.5cm K gepanzerte Selbstfahrlafette IVa (Dicker Max)

[cbo]

"Encyclopedia of German tanks..." article for the vehicle has 132mm vs 0 degrees and 111mm vs 30 degrees at 2000 meters. Ammo not specified. Appendix in the same book has similar figures for the same gun - the 10,5cm K18. All 30 degrees with PzGr Rot (ABCBC according to Hogg)

100m - 164mm
500m - 149mm
1000m - 133mm
1500m - 119mm
2000m - 109mm

With 164mm at 100m and 30 degrees, I would think that 0 degree penetrations would be more like 190-200mm point blank?

[RecruitMonty]

Anyone here know how to calculate the difference between armour penetration values at 30 degrees and at 0 degrees? There has to be a formula for this sort of thing, right?

I'm assuming that the armour penetrated is at an angle of 0 degrees in the basic MBT/WW2 calculation, which I am also assuming means we are talking about a "flat" or vertical armour plate.

I'm kind of a novice when it comes to calculating all of this stuff.