Cruzz!
I'm back with another question concerning how bulletins and penetration/armor work.
Penetration will be percent applied on top of penetration value (ie 100*1.05). Penetration is a pretty strong bulletin (on atguns and tanks, not on MGs or mortars that have barely any to begin with) because it will apply on first shot, unlike things like reload which will only help shots following the first.
Armor is same (percent on top of normal value like 234*1.05 for okw piv), and will also apply to rear armor.