OGC:Capacity (5e Variant Rule)
From D&D Wiki
|This material is published under the OGL|
The firearm contains multiple bullets that may be fired before the weapon needs to be reloaded. When reloading, the creature may choose how many shots to load the firearm with up to its maximum capacity.
Firearms with this property do not need to reload until all shots are fired. Thus, a firearm with the Capacity property may be used to make multiple attacks in a round, but may only be fired once as an action, bonus action, or reaction during the same round in which it is reloaded.