Boomstick

A firearm with a long + wide barrel. When
fired shoots a 15ft cone of fiery debris. Each
creature must make a DC16 Dex save. 4d6 fire
damage or half as much on a success.
The barrel remains quite hot after use and can
only be used twice daily. On a 3rd use the barrel
will explode destroying the weapon and dealing
8d6 fire damage to all in a 5ft radius.