Arcane Rocket Launcher

You conjure a imaginative magic shotgun in your hand, for 2 rounds, your hands can shoot sprays of bullets of magical force. you can use your Attack action to fire one Rocket per attack. The rocket explodes in a 15‑ft radius. Each creature in that area must make a Dexterity saving throw. A creature takes 6d6 fire damage on a failed save, or half as much on a successful one.

Using a Higher-Level Spell Slot. The spell adds 2d6 fire dmg for each spell slot level above 4.