Armor-Piercing
Armor-Piercing ammunition is used solely in standard autocannons. The improved materials and warheads enable the munitions to damage vulnerable components without breaching an enemy's armor. This comes at the price of being more bulky and less accurate.
In game terms, AP ammo suffers a +1 to hit modifier and an ammo bin carrying AP ammunition can only carry half as many rounds (round down). The advantage is that it gains a critical hit chance, even without striking the internal structure, though it suffers a negative modifier to the roll that becomes more detrimental and the size of the autocannon gets smaller.