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.
APx Each time a friendly operative makes a shooting attack with this weapon, subtract x from the Defence of the target for that shooting attack. x is the number after the weapon's AP, e.g. AP1. If two different APx special rules would be in effect for a shooting attack, they are not cumulative - the attacker selects which one to use.