This weapon does not require you to hold any ammunition as it regenerates its own. 

The weapon's properties are Reload 10, misfire 3

Instead of the weapon needing to be repaired whenever it misfires, instead, The Board Of Directors becomes displeased with your performance on the battlefield, causing you to hear voices and yelling in your mind, making you take 3d8 psychic damage

In order to attune to The Service Weapon, you need to spend an hour meditating over the weapon, which puts you through a dream sequence that teaches you how to use the weapon and also connecting you with the entities that have bestowed it upon you, these entities are known as "The Board Of Directors".

While attuned to the weapon, you gain proficiency in the Intelligence (Religion) skill and you gain a +3 to damage and attack rolls.

 

Firearms are a new and volatile technology, and as such bring their own unique set of weapon properties. Some properties are followed by a number, and this number signifies an element of that property (outlined below). These properties replace the optional ones presented in the Dungeon Master’s Guide. Firearms are ranged weapons.

Reload. The weapon can be fired a number of times equal to its Reload score before you must spend 1 attack or 1 action to reload. You must have one free hand to reload a firearm.

Misfire. Whenever you make an attack roll with a firearm, and the dice roll is equal to or lower than the weapon’s Misfire score, the weapon misfires. The attack misses, and the weapon cannot be used again until you spend an action to try and repair it. To repair your firearm, you must make a successful Tinker’s Tools check (DC equal to 8 + misfire score). If your check fails, the weapon is broken and must be mended out of combat at a quarter of the cost of the firearm. Creatures who use a firearm without being proficient increase the weapon’s misfire score by 1.

Explosive. Upon a hit, everything within 5 ft of the target must make a Dexterity saving throw (DC equal to 8 + your proficiency bonus + your Dexterity modifier) or suffer 1d8 fire damage. If the weapon misses, the ammunition fails to detonate, or bounces away harmlessly before doing so.

Ammunition

All firearms require ammunition to make an attack, and due to their rare nature, ammunition may be near impossible to find or purchase. However, if materials are gathered, you can craft ammunition yourself using your Tinker’s Tools at half the cost. Each firearm uses its own unique ammunition and is generally sold or crafted in batches listed below next to the price.

THIS IS UNOFFICIAL MATERIAL

These game mechanics are usable in your campaign if your DM allows them but not refined by final game design and editing. They aren’t officially part of the Dungeons & Dragons game and aren’t permitted in D&D Adventurers League events unless otherwise stated.

Notes: Proficiency: Religion, Bonus: Magic, Ignore Weapon Property: Two-Handed, Hour long meditation, Combat, Two-Handed, Reload, Misfire