You have a +1 bonus to attack and damage rolls made with this magic weapon.
There is a slot in this gun where you can put a cartridge that costs 10 GP, that can be swapped out that adds an extra D6 of a specific type of damage (Acid, Lightning, Fire, Cold, Psychic, Poison, Radiant, Thunder, Necrosis), that can be added to the roll. This gun is pretty hard to find and expensive to buy (1000 GP), but can be invaluable in a battle.
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.
This weapon has the following mastery property. To use this property, you must have a feature that lets you use it.
Vex. If you hit a creature with this weapon and deal damage to the creature, you have Advantage on your next attack roll against that creature before the end of your next turn.
Notes: Bonus: Magic, Damage: Acid, This magical pistol needs to be able to draw on your magic when it does not have a cartridge in. , Damage, Combat, Range, Ammunition (Firearms), Reload, Vex