At 3rd level you story led you to make a deal (Willing or not) with a Celestial being. This gives you boons of the deal. When an enemy makes an attack against you with a ranged attack, you may use your reaction to roll a d6 and fire a shot from a fire arm. On a roll of 1 or 2 you gain a +3 to your AC vs the attack.
Heavenly Fighting Style
At 7th level you gain an improved fighting style.
Dueling → Divine Shot
When you make an attack with a pistol and your wielding nothing else you may have it deal bonus radiant damage equal to you CHA Modifier.
Sharpshot → Vigilant Eye
Once per round you may use your rifle to make an attack of opportunity, but your range with the attacks of opportunity are half that of a normal attack.
Boomstick → Divine Spliter
When you are wielding a shotgun your standard range becomes your standard attack range + 1/2 your standard attack range. This doesnt change your long range.
Twin Pistols → Twin Angels
When you are dual wielding pistols you may charge the loaded shot in each pistol. If these shots hit an enemy they deal extra radiant damage equal to your proficentcy bonus. You can use this a number of times per day equal to your proficentcy bonus.
At 11th level you may form a bond with a shotgun, rifle or 1 or 2 pistols. They deal half radiant damage and half piercing. When this weapon is seperated from you, you may call it to your hand as a bonus action. This weapon gains a +1 to attack and damage rolls and is magical. You may casue this item to radiate light out to 30ft and dim light out to 60 by using an action on your turn to activate or deactivate this effect.
At 15th level you have attained the form of an Angelic Gunslinger. You have resistance from radiant damage and piercing/slashing/blugeoning from non magical sources. You aslo sprout angelic wings that allow you to fly at your land speed but you cannot fly in heavy armor.