They do not consume any type of ammunition and can be fired indefinitely.
Each gun does the same amount of damage as a regular flintlock; damage of the bullets are fixed, albeit varies depending on which area you hit the target in; head shot being 600 damage, torso being 450 damage, and any other limb being 300 damage. You can fire two shots before reloading, but reload time is slightly longer.
Drake, Guard Captain of Alalea, is famous for using this weapon, but it is not available as a boss drop from him on death.
[Left Click] - The user shoots the gun on the right. Clicking again shoots the one on the left. Both guns reload at the same time, as soon as both are fired. However, there is a small gap between each reload.