Repeating Shot

Source: Eberron - Forge of the Artificer

Weapon (Any Simple or Martial with the Ammunition Property), Uncommon (Requires Attunement)

This magic weapon grants a +1 bonus to attack and damage rolls made with it when it’s used to make a ranged attack, and it ignores the Loading property if it has that property.

If the weapon lacks ammunition, it produces its own, automatically creating one piece of magic ammunition when the wielder makes a ranged attack roll with it. The ammunition created by the weapon vanishes the instant after it hits or misses a target.