Editing Warhammer 40,000/9th Edition Tactics/Weapons (section)

===AP Chart===
*'''AP 0''': No armour penetration abilities to speak of. Present in the most basic weapons of the game or in weaponless melee. It will allow pretty much any unit a good chance to survive unless they are 6/7+ save. Will only wound MEQ and higher with a lot of spam. 
*'''AP -1''': The most basic AP possible. Will dent the enemy's save enough to slightly increase your killing potential but still won't guarantee anything against MEQ or higher, and a bunch of special rules blocks it specifically to boot. 
*'''AP -2''': Now we're going somewhere. AP-2 will make a dent on MEQs, TEQs, and Vehicles, giving you a good chance of wounding them. Will probably go through the save of most GEQs and definitively will blow up anything weaker than that.
*'''AP -3''': Great armour penetration. This level of penetration, most frequent in plasma or power weapons, is usually enough to deal with most things since even 3+ saves will barely survive most attacks with this ap. This is ''generally'' the starting point for invulnerable saves to start blunting your penetration, so this is enough to kill most units. 
*'''AP -4''': Melta and lascannon tier. This will go through 3+ saves with no problem. Most weapons with this kind of AP have a lot of damage output but will have very few attacks to compensate.
*'''AP -5''': "Fuck my shit up" levels of damage. Extraordinarily rare levels of armour penetration, nothing without invulnerable saves or a ''very'' good armor save (e.g. 2+ in light/heavy cover) can stop this level of raw power. Expect it on rare, heavily buffed, and/or titan-grade weapons.
*'''AP -6''': The maximum level of AP logically allowed by the rules, straight-up denying the enemy any armor save, even in cover, forcing them to rely on invulnerable saves or forcing them to hope that the attacker flubs the wound rolls.  It's still possible for an armor save to be so good this doesn't evaporate it, because some armies can take a Sv2+ model, put it in light/heavy cover, and then apply 1 or more additional additive modifiers, but that's super rare.

====Non-numeric Penetration====
*Some weapons/models/other special rules ignore Light Cover or ignore Cover period (which covers Light, Heavy, and Dense, the first 2 of which modify armor saves); when present, a rule like this is not as good as decreasing your AP by 1, but better than not having the rule, in terms of penetration only (ignoring Dense Cover is also helpful but not relevant to penetrating armor).
*Some weapons ignore all armor saves, which is incredibly rare and when present will be a special rule on the weapon or model, rather than represented in the AP column of the weapon profile.  This will, of course, bypass even the saves an AP-6 weapon can't completely ignore.
*Some weapons ignore all ''invulnerable'' saves.  This is not nearly as rare as it should be, but like ignoring all armor saves, will always be present as a special rule rather than listed in the AP column of a weapon profile.