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

==A guide to Armour Piercing==
In a world where you may only have access to low strength weaponry, it may not matter if you have a lot of armour piercing on your weapon. To begin with, lets have a look at your success rates against different armour saves.
*2+ is 16.66% success chance
*3+ is 33.33% success chance
*4+ is 50% success chance
*5+ is 66.66% success chance
*6+ is 83.33% success chance
*No armour save (7+) 100% success chance

As you already know, the worse a units armour save is, the better your chance of success. Armour saves are unusual as they're the only save which every unit can take, but which there can be a 100% chance to fail. Even units with no save technically have a 7+ save or worse. This is so their save can be buffed by cover, as otherwise they'd never benefit from those kinds of buffs.

So how do you get around these saves? Armour piercing on weapons can make a huge difference by allowing you to damage a unit. Lets look at the different levels of ap:
*'''Ap0''', bolters, lasguns, your opponent gets a full save roll, making these weapons only useful through sheer rate of fire. You also find it on some higher strength weapons, but these weapons will have some kind of other ability attached to them which make them worthwhile.
*'''Ap-1''', your heavy bolter/flamers, chainswords, autocannons etc. Really the absolute minimum you want to be running on a weapon, even then most of your shots will be blocked by the enemy armour, unless you're bringing this in volume fire. It can be useful, which will be discussed below.
*'''Ap-2''', battle cannons, the vulcan mega bolter etc. Bloody useful as you're now ignoring guard cardboard armour, and light vehicles don't get most of their save. Incredibly useful against knights (see below).
*'''Ap-3''', power swords, most plasma, armour piercing guard cannons etc. The most versatile as now the best save anyone can get against you is a 5+, light vehicles loose all their protection, and those pesky GEQ's with a 4+ save are now put back in their place.
*'''Ap-4''', high power plasma, all meltas and some melee weapons. The power armour destroyer, and makes a mockery of all vehicles.
*'''Ap-5''', Titan grade weapons, both ranged and melee. Cuts through all armour in the game unless it's somehow buffed.
*'''Ap-6''', doesn't exist anymore, but used to be found only on the most powerful titan weapons, or back in 7th edition and earlier, where it was ap1.

Now, you might immediately say that you want the best ap value you can get your greasy mittens on. However, you cannot talk about armour piercing values without talking about invulnerability saves as well. Invulnerability saves can always be taken (unless something says that it ignores or modifies it). In the fluff this is is explained as being a kind of force field, psychic powers, or even just the belief that the unit with it couldn't be harmed. In apocalypse, your biggest threats are those units which have some kind of invulnerability save, as when you're in a world where there are high strength, high ap and high damage weapons running around, your only defence against not being instantly destroyed is an invulnerability save.

Invulnerability saves make it so that your high ap weapons are basically wasted on your target (guilliman with high insane 3+ invulnerability save being a prime example), so you have to think about the ap of your weapons more carefully. So lets have a look at the potential invulnerability saves a unit can have, and what ap to use on them:
*'''2+''', only exists on that one stupid dark elves relic. As the target is a toughness 3 pointy eared prick, just blast them with bolter fire until they fail a save, and lose their invulnerability save as a result.