Weapon Modifications

The majority of the listed firearms can have modifications applied to them to further enhance their abilities. The modifications can affect both the weapon's visuals and mechanics.
Depending on the type of game that you are running, the modifications might affect either the material cost of crafting the firearm or the cost of manufacturing the firearm / modification.
For certain modifications, the base cost of the firearm might affect the cost of the modification and will be listed to the appropriate modifications. The cost of a firearm with multiple modifications of these types does stack.
Improved Iron Sights Iron sights with improved visibility. +1 to attack rolls.
Scope A specially crafted glass scope ranging in length. When viewing through the scope in combat, attack rolls made within far range do not have disadvantage, but attack rolls made within normal range have disadvantage.
A scope can also double as basic binoculars, granting advantage on Perception checks within the normal range of the weapon.
Rifled Barrel(s) Excludes: Blunderbuss weapons and the Hand Cannon
Cost: 1/4 Base Weapon cost
Spiral grooved patterns on the inside of the barrel designed to spin the ball making it more accurate. +1 to attack rolls for all barrels.
Extended Barrel Extends the barrel of the firearm, adding an extra 10ft of range to the firearm. For area focused firearms, the area of effect is decreased by 5ft.
Detachable Cylinder Only Includes: Pepper-Box and Pepper-Box Rifle
Modified Pepper Box with a detachable cylinder, which allows the shooter to reload much faster. Takes one action to reload all barrels rather than one action per barrel.
Breechlock Mechanism Excludes: Light Firearms, Volley Gun, Pepper-Box Rifle
Cost: 2x Base Weapon cost
Replaces the muzzleloading mechanism with a cartridge mechanism. Rather than shooting a lead ball or an equivalent ammunition, the firearm must shoot pre-packed carttidges. Loaded cartridges can be loaded into the breech of the firearm, reducing the reload speed for each barrel by one action.
Bronze Firearms Cost: 3x Base Weapon cost
Firearms with a bronze cast barrel instead of an iron cast barrel. Misfire Score decreases by one to a maximum of one