The Gunner can apply several different attachments to their firearms, altering their properties, damage, or function. Here is a list of the available firearm attachments, categorized into five types: Barrel, Melee, Muzzle, Sights, and Miscellaneous.

In addition, some attachments gain upgraded effects at certain Gunner class levels, while others require the Gunner to be at least a certain level to apply them in the first place.

Barrel Attachments

Extended Barrel

This barrel has been elongated to increase accuracy and range. The normal range of a firearm with this attachment increases by 20 feet, and its long range increases by 60 feet.

When you reach 11th level in the Gunner class, the normal range instead increases by 40 feet, and the long range by 120 feet.

Sawed-Off Barrel

This barrel has been cut short to facilitate close-quarters combat. Being within 5 feet of a hostile creature doesn’t impose Disadvantage on ranged attack rolls using a firearm. The normal and long ranges of the firearm are both halved (calculated after other attachments that affect range).

Subaquatic Barrel

This barrel has been improved to fire underwater. Attacks made using a firearm with this attachment ignore the penalties of underwater combat.

Wide Barrel (9th Level)

This wide barrel allows for larger bullets with more stopping power. When you hit a Large or smaller creature with a ranged attack using a firearm with this attachment, the creature is pushed 5 feet directly away from you. If you hit it a second time on the same turn, you can choose to push it another 5 feet or knock it Prone. If you roll a 1 on an attack roll made using the firearm, you’re pushed 5 feet directly away from your target.

When you reach 15th level in the Gunner class, this effect applies to Huge or smaller creatures.

High-Velocity Barrel (11th Level)

This magitech barrel accelerates projectiles to near impossible speeds. Ranged attacks made using a firearm with this attachment pass through the first creature or object they hit, as long as it’s Medium or smaller and less than 2 feet thick. If there’s another creature or object no more than 5 feet directly behind the original one, you can target it with the attack as well, making a new attack roll. This attack roll ignores any cover provided by the first creature or object.

When you reach 15th level in the Gunner class, ranged attacks made using a firearm with this attachment pass through magical barriers such as those created by the Tiny Hut, Wall of Force, and Forcecage spells, and ignore the effects of the Shield spell.

Double Barrel (15th Level)

This extra barrel makes a firearm twice as dangerous. Attacks made using a firearm with this attachment deal an extra die of damage on a hit. The Reload value of the firearm is halved (calculated after other attachments that affect Reload). This attachment can’t be applied to firearms with Reload (1).

Sights Attachments

Adamantine Sights

Being Prone or targeting a Prone creature more than 5 feet away doesn’t impose Disadvantage on ranged attack rolls made using a firearm with this attachment.

Arcanovision Sights (9th Level)

While looking through this attachment, you see an aura around visible creatures or objects within 30 feet of you that bear magic, as per the Detect Magic spell.

When you reach 15th level in the Gunner class, you can’t have Disadvantage on ranged attack rolls using the firearm against creatures or objects bearing the aura.

Auto-Targeting Sights (9th Level)

When you make a ranged attack roll using a firearm with this attachment against a creature you can see, you can choose not to roll, but instead treat it as if you’d rolled a 10 on the d20. Once you use this attachment, you can’t do it again until you use an action to reset the mechanism.

Night Vision Sights

You have Darkvision out to 60 feet while looking through this attachment. When you reach 15th level in the Gunner class, you can also see normally in magical Darkness out to 60 feet while looking through this attachment.

Telescopic Sights

Attacking at long range doesn’t impose Disadvantage on ranged weapon attack rolls made using a firearm with this attachment. The attachment also functions as a Spyglass.

Thermal Sights (9th Level)

While looking through this attachment, you have Advantage on Wisdom (Perception) checks made to detect creatures that produce body heat, and you can always see those creatures regardless of light conditions or obscurement, as long as they’re not behind Total Cover. Some Constructs, Elementals, and Undead exist at ambient temperature and can’t be seen with this property (GM’s discretion).

Melee Attachments

Bayonet

This knife, spike, or similar implement allows you to use your firearm as a melee weapon. A firearm with this attachment is also considered a Simple Melee weapon. It deals 1d4 Piercing damage on a hit, and you can use your Dexterity modifier instead of Strength for the attack and damage rolls of melee attacks made with it.

The damage of this attachment increases to 1d6 when you reach 5th level in the Gunner class, and again to 1d8 when you reach 11th level in the Gunner class.

Taser

This metal rod crackles with electricity. A firearm with this attachment is also considered a Simple Melee weapon. It deals 1 Lightning damage on a hit, and you can use your Dexterity modifier instead of Strength for the attack and damage rolls of melee attacks made with it. If a creature takes damage from this attachment, it can’t take Reactions until the start of its next turn.

The damage of this attachment increases to 1d4 when you reach 9th level in the Gunner class, and again to a 1d6 when you reach 15th level in the Gunner class.

Grapplehook (5th Level)

This sharp hook is connected to the firearm by a short length of chain. A firearm with this attachment is also considered a Simple Melee weapon. It deals 1d4 Piercing damage on a hit, and you can use your Dexterity modifier instead of Strength for the attack and damage rolls of melee attacks made with it. A Medium or smaller creature hit with a melee attack using the firearm with this attachment has the hook embedded in it, and can’t move farther than 10 feet away from you until it or a creature within reach of it uses an action to remove the hook, until you move farther than 10 feet from it, or until you make a melee attack with the firearm against a different creature. You can use a Bonus Action to reel a creature with a hook embedded in it 5 feet towards you.

When you reach 11th level in the Gunner class, the hook can embed itself in Large or smaller creatures.

Needle (5th Level)

This attachment consists of a hollow needle filled with venomous fluid. A firearm with this attachment is also considered a Simple Melee weapon. It deals 1 Piercing damage on a hit, and you can use your Dexterity modifier instead of Strength for the attack and damage rolls of melee attacks made with it. When you hit a creature with a melee attack using it, the creature becomes Poisoned until the end of its next turn. After this effect triggers, it can’t trigger again until you use an action to reset the mechanism.

This attachment deals an extra 1d4 Poison damage on a hit with the melee weapon when you reach 11th level in the Gunner class.

Buckler (9th Level)

This attachment consists of a small shield mounted to the barrel. You gain a +1 bonus to AC while holding a firearm with this attachment.

Weighted Butt (9th Level)

This attachment has a dangerous heft to it. A firearm with this attachment is also considered a Simple Melee weapon. It deals 1d4 Bludgeoning damage on a hit, and you can use your Dexterity modifier instead of Strength for the attack and damage rolls of melee attacks made with it. When you roll a 4 on the damage die against a creature, the creature is dazed, gaining Disadvantage on the next attack roll it makes before the end of its next turn.

When you reach 15th level in the Gunner class, this damage increases to 1d6, and you daze a creature on a roll of 5 or higher.

Muzzle Attachments

Scattershot

This attachment breaks bullets into a shower of shrapnel as they exit the barrel. A firearm with this attachment loses its normal and long ranges, and can’t be used to make ranged attack rolls against creatures. Instead, you can use an action to fire shrapnel from it in a 15-foot Cone, making a ranged attack roll. Each creature in the area must succeed on a Dexterity saving throw with the DC equal to the result of your attack roll or take the damage of the attack. Magical ammunition can’t be fired by a firearm with this attachment, and mundane bullets fired from it are destroyed.

When you reach 11th level in the Gunner class, the area increases to a 20-foot Cone.

Suppressor

A firearm with this attachment loses the Loud property.

When you reach 11th level in the Gunner class, making an attack with a firearm using this attachment while hiding doesn’t reveal you to creatures outside of the firearm’s normal range.

Muzzle Flash (5th Level)

When you make the first ranged weapon attack using a firearm with this attachment after reloading it, the muzzle produces a blinding flash. Each other creature within 5 feet of you gains Disadvantage on the next attack roll it makes before the end of its next turn. Creatures with Immunity to the Blinded condition ignore this effect.

Red-Hot Muzzle (5th Level)

This muzzle is built with a deliberate fault that causes it to overheat. When you make the first ranged weapon attack using a firearm with this attachment after it’s reloaded, the muzzle becomes incandescent until the firearm is reloaded again or until you hit with a melee attack using the firearm. A melee attack made using a firearm with an incandescent muzzle deals an extra 1d6 Fire damage on a hit.

When you reach 11th level in the Gunner class, this damage increases to 1d8.

Concentration Breaker (9th Level)

This muzzle imbues bullets that pass through it with anti-magic properties. Creatures have Disadvantage on Constitution saving throws made to maintain Concentration as a result of taking damage from a ranged weapon attack using a firearm with this attachment.

Force Pulse (9th Level)

When you make the first ranged weapon attack using a firearm with this attachment after it’s reloaded, the muzzle produces a pulse of repelling force. Each other Medium or smaller creature within 5 feet of you is pushed 5 feet directly away from you.

When you reach 11th level in the Gunner class, this effect applies to Large or smaller creatures. When you reach 15th level in the Gunner class, this effect applies to Huge or smaller creatures.

Miscellaneous Attachments

Automatic Reloader

The first time that a firearm with this attachment needs to be reloaded, the attachment reloads it automatically (no action required). After this attachment triggers, it can’t trigger again until you spend an action resetting the mechanism.

Decorative Etchings

While visibly holding a firearm with this attachment, you have Advantage on Charisma (Intimidation) and Charisma (Persuasion) checks.

Extended Capacity

A firearm with this attachment has its Reload value increased by 1, to a maximum of 6.

The Reload value increases by an additional 1 when you reach 5th, 11th, and 15th levels in the Gunner class.

Smart Grip

You can’t be disarmed of or otherwise forced to drop a firearm with this attachment.

When you reach 11th level in the Gunner class, you can’t have Disadvantage on melee attack rolls made using a firearm with this attachment.

Arcane Stabilizer (5th Level)

A firearm with this attachment is considered magical for the purposes of overcoming resistance and immunity to nonmagical attacks and damage. This also applies to attacks made using Melee attachments.

When you reach 11th Level in the Gunner class, the firearm with this attachment gains a +1 bonus to attack and damage rolls made with it. If the firearm already has a bonus to attack and damage rolls, you use the highest of the two. When you reach 15th level in the Gunner class, this bonus increases to +2.

Bipod (9th Level)

As an action or Bonus Action while standing on the ground and holding a firearm with this attachment, you can unfold and mount a bipod to aid in your aiming. While you remain in the same space with the bipod unfolded, you have Advantage on the first ranged attack roll you make using the firearm on each of your turns. You can fold the bipod back in using an action or Bonus Action. If you move or are moved without first folding the bipod, you have Disadvantage on attack rolls made using the firearm until the bipod is folded.

Heat Sink (15th Level)

This attachment allows you to overheat your firearm in order to push it past its limits. When you attack using a firearm with this attachment as part of the Attack action, you can choose to make an additional attack as part of the same action, taking 3d6 Fire damage as the weapon overheats. If you take any of this Fire damage, you have Disadvantage on the attack roll. After you use this effect, you can’t do so again until you use an action to vent the excess heat.