These are intended for campaigns in which firearms are the main weapons and a technology level of around 1700-1900. These rules favor ranged combat over melee, and gimp the bow. I intended this when writing these rules. Aside from replacing Armor Training/Mastery for the Fighter and giving Barbarians the option of increasing Dex instead of Str in rage (hyper battle focus), the classes should work all right with these rules, though a bit of tweaking here and there may be necessary. Note that I say the classes should work fine, not that they do. I can't promise anything, especially where the Druid is concerned. These rules contain references to a homebrew campaign setting, but you guys may use them as you wish.
The UC firearm rules are not used here. These rules are a replacement for campaigns where firearms are not intended to be balanced with melee combat. There are no misfire chances, firearm prices are around that of a good crossbow, and damage is generally around 1d8 for pistols, 1d12 for longarms, and 2d8 for shotguns.
Firearms are simple weapons. All classes, even those not proficient with all simple weapons, are proficient. Bows are exotic weapons and cannot be sized for more than +1 strength.
All characters with the requisite BAB gain the Vital Strike feats as free bonus feats. These feats allow you to roll extra damage instead of full attacking, and are useful with firearms do to their reloading times. The Vital Strike feats, under these rules, apply magical properties and Str/Dex to each damage roll instead of applying them only once. Haste and other effects that add extra attacks add rolls to Vital Strike. If you have a class feature that allows you to move and full attack on the same turn you instead gain another action (either move or standard) that cannot be used for an attack whenever you use this class feature.
Most firearms have either break open single shot actions or revolving ammunition cylinders and load from the breech. Earlier guns generally use alchemical cartridges, later guns use metal cartridges.
Almost all guns have rifled barrels. Armor is obsolete, and replaced by the defense bonus system from Unearthed Arcana. Reloading a firearm is a move action unless otherwise specified in the weapon's description. The rapid reload feat or alchemical or metal cartridges (which are the norm) reduces this to a free action.
Add your dexterity modifier to all firearm damage rolls with one handed firearms, one half your dexterity modifier for firearms held in your off hand, and one and a half times your dexterity modifier to firearm damage rolls with two handed firearms. You may grip a one handed firearm with two hands to treat it as a two handed firearm for this purpose.
Attaching a bayonet to a weapon is a move action. The weapon must be a two handed firearm (pistol bayonets exist, but are fairly useless) with a bayonet lug. While the bayonet is attached you take a -2 penalty to all ranged attack rolls with the weapon due to the bayonet messing with the weapon's balance. A bayonet deals 1d6 piercing damage with a 20/x2 critical and weighs 2 pounds, and is treated as a two handed melee attack. A firearm with a bayonet attached has a 10 foot reach, but unlike most reach weapons can strike opponents adjacent to the wielder, but at a -5 penalty to attack rolls. A bayonet can be braced against a charge.
You may strike an opponent with the butt of a firearm. Two handed firearms do 1d6 damage and one handed firearms do 1d4 damage. This is bludgeoning damage, and the critical threat is 20/x2.
A character proficient with a firearm is also proficient with an attached bayonet or when using the butt as a weapon.
If a weapon is capable of automatic fire, you may use this setting. Make an attack roll against a 10 by 10 foot area. If successful, everything in the area must make a reflex save of DC 10 plus twice the shooter's dexterity modifier or take full damage from the attack. You must fire 10 rounds to use automatic fire. If you cannot do this, you may not use automatic fire.
If you successfully hit a target with 3/4 or 9/10 cover with a ranged attack, you treat your roll as being 5 higher than it actually was for the purpose of determining whether you threaten a critical hit and for the purpose of confirming the critical hit. This is because a target with that much cover is likely only exposing the head or upper chest, so while that person is harder to hit with gunfire, any shot that does hit is very likely to have hit something vital.
Making a charge attack against or moving into melee range of somebody armed with a firearm provokes an attack of opportunity from that person. This attack is made halfway through the charge or movement, and if hit you must make a fortitude save against DC 15 plus the dexterity bonus the shooter applied to the attack or stop your movement immediately. If you are within 10 feet of the person armed with a firearm and move into melee range you do not provoke an attack of opportunity from them. This the only time ranged attacks of opportunity may be made.
Shotguns are not area effect weapons. They are aimed at a specific target. Unlike with other two handed ranged attacks, shotguns add full dexterity to attack and damage rolls, not 1 1/2 times dexterity. This is because shotguns are not precision weapons. However, shotguns are not difficult to aim, and the target takes a 1d4 penalty to defense (which is one's armor class). Shotguns do 2d8 damage with a 20 foot range increment, have a capacity of one for single barrel and two for double barrel designs, and have the weights and prices listed above. They are two handed weapons, and cannot be used for full attacks.
Some feats or class features that are designed for crossbows would logically function with guns. The GM is the arbiter of this.
Like them? Would you use a firearm with these rules? Did I make guns dominant over melee like I intended?