Firearms

Class Proficiencies 

Barbarian   

• Double-barrel shotgun, Simple blasters, blitz cannon, magnus, REC gun, volcanic 

Bard 

• Light revolver, parlor gun, Simple blasters

Cleric 

• Simple blasters 

Druid 

• Hunting rifle 

Fighter 

• Lever-action shotgun, light revolver, repeating rifle, revolver, Simple blasters, martial blasters 

Monk 

•  Simple blasters

Ranger 

• Hunting rifle, revolver 

Rogue 

• Coach gun, light revolver, parlor gun, Simple blasters 

Sorcerer 

• Phaser, Psionic helm, Repeater, Swarm pistol

Wizard 

• Simple blasters 

Damage Rolls with Firearms 

Unlike other weapons, you don't add your ability modifier to the damage roll of a firearm unless otherwise stated. 

Two-Weapon Fighting with Firearms 

Unlike other ranged weapons, you can engage in two-weapon fighting with two light firearms. When you do so, you subtract 2 from the damage roll of the bonus attack, to a minimum of 1 damage. 

Firearm Properties 

All firearms produce a loud boom, audible out to half a mile. In addition, firearms require special ammunition and some of them have additional special properties. 
     Ammunition. The ammunition of a firearm is destroyed upon use. Firearms use bullets, scatter firearms use shells, and cannons use cannonballs. 
     Concealable. You have advantage on Dexterity (Sleight of Hand) checks made to hide this weapon. 
     Mounted. This weapon is normally used while attached to a tripod, wagon, or other bracing mount. While it is mounted, it can't be moved. You can mount or unmount this weapon as an action. While it is unmounted and the creature wielding it is not prone, this weapon can only be used proficiently by a Medium or larger creature with a Strength score of at least 17. 
     Reload. A limited number of shots can be made with a weapon that has the reload property. If you are not proficient with the firearm, you must then use your action to reload it. If you are proficient, you can choose to use your bonus action to reload instead. 
     Scatter. If you make an attack within this weapon’s normal range, you deal an additional die of weapon damage. 

Special Firearms

Firearms with special rules are described here. 
     Gatling Gun. As an action, you can rapidly fire at an area rather than a single target. Select a 15-foot cube within the weapon's range. Each creature in that area must make a DC 15 Dexterity saving throw or take damage as if hit by this weapon's attack, or half as much on a successful saving throw. This action uses 10 round of ammunition. 
     Light Cannon. An attack with this weapon can target a space within range, which is treated as having 10 AC. On a hit, each creature within 5 feet of the point of impact must make a DC 14 Dexterity saving throw or take half the damage rolled.