Most warriors and combat specialists spend their years perfecting the classic arts of swordplay, archery, or pole arm tactics. Whether duelist or infantry, martial weapons were seemingly perfected long ago, and the true challenge is to master them. However, some minds couldn’t stop with the innovation of the crossbow. Experimentation with alchemical components and rare metals have unlocked the secrets of controlled explosive force. The few who survive these trials of ingenuity may become the first to create, and deftly wield, the first firearms.
Source: D&D Beyond
Starting when you choose this archetype at 3rd level, you gain proficiency with firearms, allowing you to add your proficiency bonus to attacks made with firearms.
Upon choosing this archetype at 3rd level, you gain proficiency with Tinker’s Tools. You may use them to craft ammunition at half the cost, repair damaged firearms, or even draft and create new ones (DM’s discretion). Some extremely experimental and intricate firearms are only available through crafting.
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. These properties replace the optional ones presented in the Dungeon Master’s Guide. Firearms are ranged weapons.
When you choose this archetype at 3rd level, you learn to perform powerful trick shots to disable or damage your opponents using your firearms.
Trick Shots. You learn two trick shots of your choice. Many maneuvers enhance an attack in some way. Each use of a trick shot must be declared before the attack roll is made. You can use only one trick shot per attack. You learn an additional trick shot of your choice at 7th, 10th, 15th, and 18th level. Each time you learn a new trick shot, you can also replace one trick shot you know with a different one.
Grit. You gain a number of grit points equal to your Wisdom modifier (minimum of 1). You regain 1 expended grit point each time you roll a 20 on the d20 roll for an attack with a firearm, or deal a killing blow with a firearm to a creature of significant threat (DM’s discretion). You regain all expended grit points after a short or long rest.
Saving Throws. Some of your trick shots require your targets to make a saving throw to resist the trick shot’s effects. The saving throw DC is calculated as follows:
Trick shot save DC = 8 + your proficiency bonus + your Dexterity modifier
When you reach 7th level, you add your proficiency bonus to your initiative. You can also stow a firearm, then draw another firearm as a single object interaction on your turn.
Upon reaching 10th level, you learn how to quickly attempt to fix a jammed gun. You can spend a grit point to attempt to repair a misfired (but not broken) firearm as a bonus action.
Starting at 15th level, you can reload any firearm as a bonus action.
At 18th level, your firearm attacks score a critical hit on a roll of 19-20, and you regain a grit point on a roll of 19 or 20 on a d20 attack roll.
Upon reaching 18th level, whenever you score a critical hit on an attack with a firearm, the target additionally suffers half of the damage from the attack at the end of its next turn.