Ok, so, this would be MY take on "modern" firearms.
I'm going to do 5 of them. A pistol, an SMG, a shotgun, an assault rifle and a sniper rifle. Before I start, let me say that I have 0 experience with real firearms, being a pacifist myself (though I have read the Pathfinder firearms rules and have both played and DMed gunslingers). Therefore, this rules are not to be taken with "verisimilitude" in mind, just with game balance. None of this weapons have missfire value if loaded by someone with the right proficiency and they get touch attacks on the first range increment.
Pistol: This works just like a revolver but with double capacity, 80ft range and upping the damage to 2d6. You could also make a high caliber gun, with the same capacity as a revolver, but with 80ft range and dealing 2d8 dmg. This is a one handed weapon, so you can dual wield them. All the other are two-handed.
SMG: Same stats as the basic pistol above, but with a range of 50ft, a capacity of 30 and the Automatic Weapon quality (to be detailed on the bottom).
Shotgun: The same as the Pathfinder shotgun, but with a capacity of 8, double range and dealing 2d6 damage. Up the damage to 2d8 and you have a higher caliber shotgun.
Assault rifle: The same as the SMG, but with a range of 120ft.
Sniper Rifle: This works like a rifle, but the range is expanded to 200ft and you only take a -1 penalty for each range increment (Far Shot negates this entirely). If you shoot a target within 50ft, you take a -4 penalty. The damage gets increased to 3d8 (enough to reliably take down 1 hd enemies).
- Automatic Weapon: When performing a full attack with this weapon, you can make one additional attack at your full base attack bonus, but all the attacks in the round take a -2 penalty. Instead of using a piece of ammunition for every shot, you spend an amount of ammo equal to the shots fired +2d3. You can combine this with Rapid Shot, taking a full -4 penalty to all attacks, but getting two extra shots.
The cost depends heavily on the type of campaign... for a gunslinger these would be quite desirable. I have NO CLUE as to what the weight of these things would be... adjust accordingly.
