Thought I'd swing by. :bandit:
Before I mothballed DoW, I actually went through the Weapons folder and sorted ALL built-in shooting weapons by AP and STR in their neat lill subfolders. I also sorted the melee weapons by power/nonpower and the wielder's strength (since most melee weapons except Power Fists and Thunder Hammer just strike with the wielder's STR).
I still have the folder structure saved on my computer, but I did mess with the weapon characteristics to fit my (sadly failed) dream mod.
I based the AP of each weapon type on tabletop. Just like in TT, we have 5 basic Infantry Armour types in DoW (from tp_infantry_low to tp_infantry_heavy_high). In TT, of course, this corresponds to the armour saves from 6+ to 2+. So, an AP5 bolter (a pistol or a tactical bolter) would have this AP table vs. infantry:
Now vs. vehicles we look at Strength of the weapon instead... the bolters' strength is 4, and I came up with this AP table:
tp_infantry_low = 100% (it pierces 6+)
tp_infantry_med = 100% (it pierces 5+)
tp_infantry_high = 50% (3 chances in 6 to pierce 4+)
tp_infantry_heavy_med = 33.33% (2 chances in 6 to pierce 3+)
tp_infantry_heavy_high = 16.67% (1 chance in 6 to pierce 2+)
tp_commander = 16.67% (assume they wear artificer armour with 2+ save)
I gave buildings the same AP values as corresponding vehicles would have (so a bolter would have 2% penetration vs. tp_building_low, 0.05% vs. tp_building_light and 0% vs. tp_building_heavy).
tp_vehicle_low = 2% (simulates 1 in 6 possibility of scoring a glancing hit on Armour 10, and then 1 in 6 possibility to destroy the vehicle)
tp_vehicle_med = 0.05% (since you CAN in theory kill a dreadnought with a bolter, this represents that small possibility)
tp_vehicle_high = 0% (try as you might, you can't beat Armour 13 or 14 with a STR 4 bolter).
I got stuck and frustrated trying to calculate the weapons' damage output and units' HP values that would simulate a WH40K battlefield, and gave up. But I think at least my AP calclulations make some sense. Use 'em if you want... albeit you probably don't care.