Board Thread:Warhammer 40k General Discussion/@comment-203.134.114.240-20130706042929/@comment-3258762-20130710113600

If the plasma pistol has spread damage, it means it would splash harmlessly against Power armor, meaning it would be pretty much useless with the only chances of damaging anything is if it happens to touch and burn through the joints.

Against Astartes, AP is what you want.