Bombardier

When one thinks of fighting, they don't often think of explosives. A bombardier changes that by unleashing volleys of area of effect damage, at the cost of a loss in their range flexibility and difficulty to threaten aerial or close range targets.

Homemade Grenades

Starting when you choose this archetype at 3rd level, you gain proficiency with tinker's tools, allowing you to craft unique grenades as part of a long rest. You craft a number of these equal to your fighter level plus your dexterity modifier per long rest, and any remaining grenades from your previous long rest become duds and no longer function. Each grenade has a range of 75 feet and a long range of 120 feet. Whenever you take the attack action you can replace one or more of your attacks with one of your grenades. Treat these attack rolls as ranged weapon attacks using your dexterity modifier, that each deal 1d4 bludgeoning damage to the target if they hit. Regardless of if they hit or miss, all creatures within 10ft of where the grenade lands must make a Dexterity saving throw (DC 8+Proficiency Bonus+Dex) or take 1d6 fire damage, taking no damage on a success. 

Thrive In Explosions

When you choose this archetype at 3rd level, your exposure to the blasts and damages from grenades lend you a helpful resilience. You are immune to the damage of your own grenades, but also have resistance to fire damage. 

Versatile Payload

When you reach 7th level, your experience with your grenades has taught you how to increase their potency. When you create your grenades, you can choose to change the extra damage from their explosion from fire to any other of the following types: acid, cold, lightning, poison, thunder. You can still choose to leave them as fire damage, and not all of your grenades need to be the same damage type. Additionally, the explosion damage from your grenades deal an additional 1d6 damage (to 2d6). 

Rapid Repair

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.

Fusillade

Starting at 15th level, you can unload your grenades with devastating speed and accuracy. When you take the attack action, if you replace every attack with one of your grenades, you may make an additional one as a bonus action. Furthermore, attacks with your grenades and their explosions now ignore any cover that isn't total cover. 

Parting Gift

At 18th level, when you are reduced to 0hp you drop half of the grenades you have left, which immediately detonate in random locations up to 15 feet away, dealing damage as normal. The creature who reduced you to 0hp this way however has disadvantage the saving throws cause by this ability.