The Gunner's Arson Shell

The next time you shoot and hit a target with a firearm while this spell is active, the target suffers the weapon's normal effects and must make a Dexterity saving throw. On a failed save, a creature takes 3d10 fire damage and is covered in sharp, flaming shards of metal shavings. At the start of each of the creature's turn until the spell ends, it takes an additional 1d10 fire damage until it or another creature within 5 feet of it uses an action to brush the shavings off or extinguish the flames, or if some other effect douses the flames (such as the target being submerged in water).

On a successful save, the creature takes half as much initial damage and is not covered in the shavings. If the target is a flammable object not being worn or carried, it is set on fire. If you shoot and miss while this spell is active, the spell is lost.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the initial damage increases by 1d10 for each slot level above 3rd.