From Sots2

A refinement to the standard driver ballistic slug, which is shaped to penetrate enemy ship armor deeper with less chance of ricochet. AP rounds can be applied to all sizes of driver guns, but does require a unique barrel for greater accuracy and range. As such, AP rounds cannot be fired from standard Mass Driver systems. AP rounds do slightly less damage and carry less kinetic impact than standard rounds of the same calibre, but are more accurate, longer ranged and suffer from deflection less often.

The research of AP Rounds opens the possibility to research the following technologies: