Stats
The Gunbreaker is a STR/CON based subclass that has access to Fighters Champion passives. Gunbreaker "ranged" attacks use STR for attack and damage rolls.

Proficiency
The Gunbreaker is proficient with heavy armor, shields, Gunblades and other martial/simple weapons. The Gunbreaker should never use any weapon other than the Gunblade. You are intended to wield a Gunblade with a shield, but you can use it as a two handed weapon or even dual wield them if you want. Other than offhand damage there's no advantage to dual wielding in terms of special shots, they all use main hand ammo and are restricted to the main hand Gunblade. You can however use offhand ammo for the regular melee/ranged attacks.

Unique Gunbreaker Weapon, The Gunblade
The Gunbreaker uses a special long sword with firearm parts attached to it, this weapon is called a Gunblade.  Most Gunbreaker ranged attacks are limited to 9m. This is a tradeoff since having a gun attached to a long blade would make it rather unwieldy and inaccurate. Also the ammunition is quite large in order to facilitate the special shots, think of them as being almost the size of a shotgun shell.  The gunblade will level with you and take you all the way to end game.

Ka
This is a class resource that all Gunslingers use to power some of their abilities.

Gunblade Mechanics / Overheat
The Gunblade grants you the OVERHEAT mechanic. Any time you deal burning or fire damage you gain 2 stacks of Overheat. You can carry a maximum of 7 stacks of Overheat.  You lose overheat at the rate of 1 stack per turn. When you are stacking Overheat you also take 1d4 Fire damage every turn. When you activate the Overheat Convergence passive toggle (on the far right of your hotbar) the next attack you do that deals fire damage will also deal bonus fire damage equal to the amount of stacks of Overheat x 2.

Progression

Level 1

• Fang Strike - first attack in a 3 move melee combo chain, does weapon damage plus level scaled bonus damage.
• Second Wind
  

• These Boots (party buff) - An AoE party buff that grants the effects of Longstrider
• Net Shot - (once per turn, 4 turn cooldown for the same target) - Fires a net that entangles an enemy for 2 turns.
• Action Surge
  

• Leaping Strike - The Gunbreaker can leap up to 9m to immediately deal weapon damage to an enemy and knock them prone for 2 turns.
• Claw Strike - second attack in a 3 move melee combo chain, does weapon damage plus level scaled bonus damage.
• Improved Critical
  

• Grapple Shot - Fires an electrified tether that pulls an enemy to your position. Compels the enemy to attack you for two turns. (Once per encounter)
• Gunbreaker Protection (reaction) - When an ally is attacked you can fire a Grapple Shot and pulls the attacking enemy to you and possibly compels them to duel you. The enemy being targeted has to be within 9m
• Flame Strike - Deals melee weapon damage and fire damage. Deals bonus fire damage if Overheated
• Flame Shot - Deals ranged weapon damage and fire damage. Deals bonus fire damage if Overheated
  

• Gunbreakers Countershot (reaction) - Interrupts an enemy spell being cast. 9m range.
• Scattergun Shot - A short range cone attack that does 1/2 weapon damage and has a chance to daze targets.
• Talon Strike - final attack in a 3 move melee combo, does weapon damage plus level scaled bonus damage.
• Gunbreaker's Prey - Same as the Hunter's Prey passives.
• Extra Attack
  

• Grease Grenade - A grenade that spreads grease in a 4m radius on impact.
• Flame Grenade - A grenade that spreads fire in a 4m radius on impact.
• Extra feat
  

• Remarkable Athlete: Jump
• Remarkable Athlete: Proficiency
• Dragonfire - (usable only during Overheat convergence) - A short range cone of fire erupts from your blade doing bonus damage based on Overheat stacks. Also causes burning for 1 turn.
  

• Gunbreaker Rescue - gives a targeted ally temporary hit points and encases them in a shield that prevents all incoming and outgoing damage for 2 turns. (usable once per short rest)
  

• Indomitable
  

•  Piercing Shot - Fires a round in a straight line for 9m hitting targets in that line that don't save (dex).
  

• Improved Extra Attack