An ornate pistol of inconceivable complexity that once belonged to an Engineer at the Forge Beyond time.

The strange handgrip incorporates metallic transfer plates that draw on the users magical potential. When attacking with this weapon, the user adds their spellcasting modifier to hit and damage rolls.

Does not require proficiency to wield.  

It’s up to you to decide whether a character has proficiency with a firearm. Characters in most D&D worlds wouldn’t have such proficiency. During their downtime, characters can use the training rules in the Player’s Handbook to acquire proficiency, assuming that they have enough ammunition to keep the weapons working while mastering their use.

Notes: Bonus: Magic, Range, Ammunition (Firearms), Reload, Vex