You have trained under many artificers and have learned how to imbue you weapon with Magical properties.

Arcane Tinkering

You gain this at 3rd level. In creating and maintaining your firearms, you gain proficiency in the Arcana skill and tinkerers tools, and in order to use them, you learn how to use firearms. Should a magical mishap occur, you need to roll an arcana check to understand the exact nature of the issue, and then a tinkerers tools check to fix it. Mechanically, whenever a magical mishap occurs, a DC of 30 is set for fixing the weapon. The arcana check reduces the DC by the amount of the check, which then aids the tinkerers tools check to fix the weapon.

 

Magical mishap

When a natural 1 is rolled when firing an Arcane firearm, a magical mishap occurs. When this happens, roll on the Sorceror wild magic table to see what occurs, and roll a flat d20 to see the state of the firearm. On a 10 or higher, the weapon merely needs a tinker, and can be fixed with a bonus action. On a 9 or lower, the weapon is damaged and needs to be fixed as described in the Arcane Tinkerer feature.

Arcane Barrel

You gain this at 3rd level.

The arcane barrel is what makes each user of arcane firearms unique. Each barrels are typically uniform in design, allowing them to be taken from old firearms and placed into new and perhaps more powerful ones. They represent their makers understanding of their weapons and techniques as well as being a source of pride for them. Before firing a firearm, a barrel has to be “loaded”. Loading takes an action. When a barrel is loaded, the firearm deals damage based on the barrel and has a special effect associated with each barrel. You can only use the special effects of each barrel 1 per long rest. Each special effect requires 3 shots worth of dragonshard powder.

When selecting this class, you gain 2 barrel options and you then gain 1 additional option at 7th, 10th and 15th level.

Fire barrel

When loaded the firearm deals an additional 1d6 fire damage. Special Effect: You can use an action to fire 3 fire bolts at any target.

Force barrel

When loaded the firearm deals an additional 1d6 force damage. Special Effect: You can use an action to fire a small wall of force. The wall is 5ft high and 5ft wide, and can act as cover or as a blockage say, filling up a door. The wall only lasts for 5 minutes or until the barrel is switched out.

Frost barrel

When loaded the firearm deals an additional 1d6 cold damage. Special Effect: You can use an action to coat an area in ice. Choose a 10 feet cube within in 50ft, that area becomes difficult terrain for 1 minute as it is coated with ice, and anyone standing in the area must make a DEX saving throw, on a fail they take 3d10 cold damage.On a success, they only take half damage

Lightning Barrel

When loaded the firearm deals and additional 1d6 lightning damage. Special Effect: You can use an action to use the lightning bolt spell as per the spell.

Radiant barrel

When loaded the firearm deals an additional 1d6 radiant damage. Special Effect: You can use your action to fire a targeted burst of light to blind targets. You choose a point within 100ft, anything within 10ft of that target makes a constitution saving throw. On a fail they are blinded and take 3d10 radiant damage, on a success they take half damage and are not blinded.

Shadow barrel

When loaded the firearm deals an additional 1d6 necrotic damage. Special Effect: You can use an action to fire a Shadow shot at a target. If the shot hits, the target must make a strength saving throw. On a failure the target takes 3d10 necrotic damage and is grappled by their own shadow. At the end on their turns they may make a saving throw to escape the shadow. On a success they take half damage and aren’t grappled.

Magic from Mayhem

when a magical mishap occurs, you can choose channel the explosive burst of magical energy into a shot. You make at attack with disadvantage against a target, and it counts as a critical on a hit. You then suffer the effects of a Magical Mishap and your Arcane Barrel is badly damaged and needs to be fixed as per the Arcane Tinkerer feature.

 

Spin the Barrel

you gain the option to Spin the Barrel as an action. Once per short rest, you can target up to a number of enemies equal to the amount to Arcane Barrels you have functioning , and make a number of shots equal to the number of Arcane Barrels you have functioning. You can spread the shots across as you like, for example making 1 shot each at 2 people and make 2 shots at a single person. After using this feature you suffer a Magical Mishap.

Speed Loading

You’ve practiced swapping barrels so much that it becomes second nature. You can now switch barrels as a bonus action.

Superior Barrel

if you finish a short rest and have only 1 or less special effects from your barrels you regenerate 1 barrel's special effect.

Dragon Barrel

your mastery of your craft reaches its pinnacle. You gain access to your final Arcane Barrel, a Dragon Barrel. The dragon barrels are based off of the 3 Progenitor dragons, Eberron, Siberys and Khyber.

Eberron, The One Between

When loaded the firearm deals an additional 1d6 force damage and 1d6 cold damage. Special Effect: You can use an action to fire an Eberron Shot. Assisted by the world around you, you deal 4d6 force and 4d6 cold damage to your target, and regain that much HP.

Khyber, The One Below

When loaded, the firearm deals an addition 1d6 necrotic damage and 1d6 fire damage. Special Effect: You can use an action to fire a Khyber Shot. If the target has an intelligence of 3 or higher, and is not a fiend, they take 4d6 necrotic damage and 4d6 fire damage and are paralysed as they experience terrible images of the Khyber. At the end of their turns they can make an intelligence saving through to escape the paralysis. 

Siberys, The One Above

When loaded the firearm deals an additional 1d6 radiant damage and 1d6 lightning damage. Special Effect: You can use an action to fire an Siberys Shot. If the target of the shot has the capacity to cast spells, they take 3d10 radiant and 3d10 lightning damage, and if they cast a spell on their next turn, the spell is countered and they retake the damage.