Thanks to extensive practice with firearms, you gain the following benefits:
Ability Score Increase. Increase your Dexterity score by 1, to a maximum of 20.
Ignore Loading. You ignore the Loading property of firearms. If you're holding one of them, you can load ammunition into it even if you lack a free hand.
Firing in Melee. Being within 5 feet of an enemy doesn't impose Disadvantage on your attack rolls with crossbows.
Dual Wielding. When you make the extra attack of the light property you can add your ability modifier to the damage of the extra attack if that attack is with a firearm that has the Light property and you aren't already adding that modifier to the damage.