MWx Each time a friendly operative makes a shooting attack with this weapon, in the Roll Attack Dice step of that shooting attack, for each critical hit retained, inflict x mortal wounds on the target. x is the number after the weapon's MW, e.g. MW3.
Px Each time a friendly operative makes a shooting attack with this weapon, in the Roll Attack Dice step of that shooting attack, if you retain any critical hits, the weapon gains the APx rule for that shooting attack. x is the number after the weapon's P, e.g. P1.