We are currently (among others) running a "Warhammer" campaign with D&D 4. Our current adventure reminded me again that firearms are not as uncommon in Warhammer as they are in D&D, so I thought up a few ways to implement them.
So, there are basically two variant implementations that might best describe the technological advances in weaponry. It's all "pressed" into the D&D 4 rules framework, so I hope it doesn't break the game balance or anything.
You can mix and match the described items to fit your idea of your technological level of firearms. I describe a few magical enhancements for firearms that are available even in the lowest levels of the heroic tier - to support the rareness of these weapons, you might restrict the availability of the enhancements to a higher level and require that a firearm must always have one of the suggest enhancements.
The basic idea is that a firearm is a mix of magical and alchemical item. So people with the Alchemist or Ritual Caster feat should be able to build them. But feel free to define them as purely alchemy or purely magic. The implementation is overall closer to a magical item, because I avoided the disconnect between "cheap" ammunition that higher level characters basically can forget to count and alchemical ammunition that might have costs like alchemical items.
You can either require the Enchant Magical Item Ritual or the Alchemist feat for any character to build a firearm.
Muzzleloaded Firearms
Muzzleloaded firearms are loaded seperately with gunpowder and bullet. The process is very slow, and it is difficult to fire more then one shot during a typical combat. They are crude compared to modern firearms, but still considered very dangerous.
The Hand Cannon - Level 1 item The hand cannon must be loaded with gunpowder and shot before being fired. Loading the weapon takes a lot of time, so it is mostly used in the beginning of a battle.
Level 1: 360 gp; Level 11: 9,000 gp; Level 21: 225.000 gp
Item Slot: Weapon (Two-Handed)
Power (Encounter - Firearm): Standard Action. Range 15/30. Attack: Dexterity +1 vs Reflex. Hit: 2d4 + Dex damage.
Level 11: Dexterity +3 vs Reflex. Damage 2d6 + Dex
Level 21: Dexterity +5 vs Reflex. Damage 2d8 + Dex
The Arbeques - Level 3 item The Arbuques is a more advanced version of the hand cannon.
Level 3: 680 gp; Level 11: 17,000 gp; Level 21: 425.000 gp
Item Slot: Weapon (Two-Handed)
Power (Encounter - Firearm): Standard Action. Range 20/40. Attack: Dexterity +1 vs Reflex. Hit: 2d6 + Dex damage.
Level 11: Dexterity +3 vs Reflex. Damage 2d8 + Dex
Level 21: Dexterity +5 vs Reflex. Damage 2d10 + Dex
The Musket - Level 5 item The Musket can be reloaded much faster then hand cannon or Arbuques.
Level 5: 1.000 gp; Level 15: 25,000 gp; Level 21: 625,000 gp
Item Slot: Weapon (Two-Handed)
Property: If you spend a standard action reloading this weapon, you can recharge its encounter power.
Power (Encounter - Firearm): Standard Action. Range 20/40. Attack: Dexterity +1 vs Reflex. Hit: 2d6 + Dex damage.
Level 11: Dexterity +3 vs Reflex. Damage 2d8 + Dex
Level 21: Dexterity +5 vs Reflex. Damage 2d10 + Dex
The Musket is basically the firewall "non-weapon-weapon" variant. It can be fired every other round (and a feat might improve this to shooting every round). The biggest disadvantage - it is not a weapon attack, so all your nice weapon powers are useless.
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Cartridge Firearms
Cartridge firearms use a combination of bullet and gunpowder, making the reload process faster and yielding more reliable results. This is a requirement for firearms as weapons.
All firearms are considered superior weapons. A two-handed firearm can be equipped with a bayonet, allowing its user to use the firearm in melee as a spear.
Pistol: Prof +3;
Dmg 1d8, Range 15/30, Price 200 gp, Weight 2 bl, Group: Firearm; Properties. High Crit, Load Minor
Rifle: Prof +3,
Dmg 2d4, Range 20/40, Price 300 gp, Group: Firearm; Properties: High Crit, Load Minor
Bayonet: Prof +2,
Dmg 1d8, Price 5 gp; Weight 1 lb; Group: Spear; Properties; Reach
Bullets (10): 20 gp
New Enhancements Repeating Firearm - Item Level 2+ Note: If you want to give your firearms a feeling of rareness, this might be the minimum required enhancement for them. The typical firearm of the old world has these properties.
Level 2: +1 - 680 gp; Level 7: +2 - 3,400 gp; Level 12: +3 - 17,000 gp
Level 18: +4 - 85,000 gp; Level 23: +5 - 425,000 gp; Level 28: +6 2,125,000 gp
Weapon: Firearms
Enhancement: Attack and Damage Rolls
Critical: +1d8 per plus
Power (Encounter - Firearm): Standard Action. Make one basic attack against the target, but the target is resolved against the lower of AC and Reflex. Regardless of success, until the end of your next turn, your square and all adjacent squares are considered obscured due to the gunpowder. (Granting concealment against attacks from any square in the burst or any attacks directed at any square in the burst.)
Semi-Automatic Firearm - Item Level 3+ This group covers revolvers and modern auto-loaders. The bullets is fed from a magazine or a cylinder, allowing a fast firing rate with minimal effort by the shooter.
Level 2: +1 - 680 gp; Level 7: +2 - 3,400 gp; Level 12: +3 - 17,000 gp
Level 18: +4 - 85,000 gp; Level 23: +5 - 425,000 gp; Level 28: +6 2,125,000 gp
Weapon: Firearms
Enhancement: Attack and Damage Rolls
Critical: +1d8 per plus
Property: You can reload this firearm as a free action.*
Power (Encounter - Firearm): Standard Action. Make two basic ranged attacks, attacking two adjacent targets. Each attack is resolved against the lower of the targets AC or Reflex Defense.
*Optional: This is pretty simple, but again, counting bullets in your magazine is a little annoying. Fell free to adapt this. Also, I don't bother to distinguish between the intracities between a revolvers "reloading" mechanism and that of a modern auto-loader pistol. I am not a gun nut! Shotgun - Item Level 4+ Shotguns can be used to use fire shot, allowing you to cover a wider area. They lack in range.
Level 4: +1 - 840 gp; Level 9: +2 - 3,400 gp; Level 14: +3 - 21,000 gp
Level 19: +4 - 85,000 gp; Level 23: +5 - 525,000 gp; Level 28: +6 2,625,000 gp
Weapon: Rifle
Enhancement: Attack and Damage Rolls
Critical: +1d10 per plus
Property: Reduce the long and short range by 5 squares each.
Power (Encounter - Firearm): Standard Action. Make a basic attack against all targets in a Close Blast 3. The attack is made against the lower of AC and Reflex of the target.
Level 14 and 19: Close Blast 4
Level 24 and 29: Close Blast 5
Full-Automatic Firearm - Item Level 5+ Automatic firearms reload bullets automatically and allow even faster firing rates then of semi-automatic weapons. The blowback from the shot, the expanding gases from the explosion, or magic allows continuous fire.
Level 5: +1 - 1,000 gp; Level 10: +2 - 5,00 gp; Level 15: +3 - 25,000 gp
Level 20: +4 - 125,000 gp; Level 25: +5 - 625,000 gp; Level 30: +6 3,125,000 gp
Weapon: Firearms
Enhancement: Attack and Damage Rolls
Critical: +1d8 per plus
Property: You can reload this firearm as a free action.
Power (Encounter - Firearm): Standard Action. Make a basic attack against all targets in a Area Burst 1 within range. The attack is made against the lower of AC and Reflex of the target.
Level 14 and 19: Area Burst 2
Level 24 and 29: Area Burst 3
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Feats Combat Engineer (Heroic)
Prerequisite: Int 13 or Skill Training in Arcana and Thievery
You gain proficiency with all firearms, siege weapons and bayonets. When making an attack with a firearm, you can substitute your Dexterity Modifier with your Intelligence Modifier for the attack and damage rolls. When making an attack with a siege weapon, you can use your Dexterity Modifier in place of your Intelligence Modifier for the attack and the damage roll.
Rifleman (Heroic)
Prerequisite: Proficiency with Firearms, Rogue
You can treat a Firearm as a crossbow for the purpose of Rogue weapon powers and sneak attack, and you can treat a Bayonet as a light blade for the purpose of Rogue weapon powers and sneak attack. When using a firearm or a bayonet, your sneak attack damage is reduced by one die.
Quickload (Heroic)
Prerequisite: Proficiency with Firearms, Dex 13+
If a firearm (including a muzzle-loader) has a reload time of a standard action, you can reload it is as a minor action. if it has a reload time of a minor action, you can reload it as a free action. You still need both hands to reload your firearm.
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