As an Action you can spend at least one Ki Point to power this weapon, or up to a maximum of 10 Ki Points
Once powered you can then make a ranged attack against a target you can see within 100 ft adding your proficiency bonus to hit.
On a hit the target takes 1D12 +3 Force Damage. For every Ki Point over 1 that you spent add a D12 to the damage roll.
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.
Slow. If you hit a creature with this weapon and deal damage to it, you can reduce its Speed by 10 feet until the start of your next turn. If the creature is hit more than once by weapons that have this property, the Speed reduction doesn’t exceed 10 feet.
Notes: Bonus: Magic, Class Restriction: Monk, Damage, Combat, Range, Two-Handed, Ammunition (Firearms), Reload, Slow