Gunpowder AP ignores shields.

There are also set base attacks for AP weapons:

One-Handed:

Maces: 8, 10, 13
Axes: 7, 9, 11
Hammers: 7, 9, 16

Two-handed:

Axes: 13, 15, 17, 20
Pollaxes: 16, 21
Bills: 13, 15
Western Halberds: 5, 9, 12
Eastern Halberds: 5, 7, 12
Swordstaves: 7
Voulges: 5, 7