All right, just something I've considered about Firearms in Pathfinder, and how armor reacts to them (that is, no AC). I'd like to propose a house rule idea for a magic armor special ability enchantment.
Bulletproof Armor. Armor and Shields with this Special ability retains (some or all) of its AC against Firearms, protecting against Firearm rounds as if they were arrows or other missiles.
Still fiddling with this concept, such as the price for such an enchantment, whether or not it should be in degrees (Like 25%/50%/75%/100% AC coverage), and other small details.
What are your opinions on this concept? Has someone else worked on an idea like this?
I would see the enchantment changing its value based on how common firearms are in the campaign, especially advanced firearms. I can't imagine this enchant in a No/Very Rare guns setting. It would be rare knowledge in an Emerging Guns setting, and growing more commonplace from there.
You could do two types of enchantments depending on how effective you want them to be.
+1 Armor Quality
Armor with Pistoleer's Bane adds its enhancement bonus to AC against attacks from a firearm, even if that attack would normally be treated as a Touch attack.
Armor with this enchant provides its full armor value against attacks from firearms. Firearm attacks are never treated as touch attacks regardless of range.
Though, since game balance was designed around firearms being a touch attack at certain Range increments, I would add a Deed for gunslingers to bypass bulletproof armor.
At 12th level, the gunslinger can spend 2 points of grit to make a single attack and resolve it as a touch attack, bypassing all forms of armor. This can be included within a full-attack action, but each armor-piercing shot must be called before the attack is rolled and the grit is spent whether the attack hits or not. The target must be within the first range increment to use this ability.