The flintlock .44 caliber 6 shot revolver is capable of rapid fire, easily emptying all six chambers in an instant. As with all firearms, the force of impact is dependent on the ammunition provided.
Mr. 5 fills the chambers with his breath, which is made explosive due to his Bomu Bomu no Mi powers. This allows him to fire invisible explosive blasts that will accumulate for devastating damage, and gives him virtually infinite ammunition. He only uses the flintlock for tougher situations, and was rather displeased that he had to use it against Usopp.
During the raid on Minion Island, Gladius was wielding a flintlock. Although the manga did not show its model up close, the anime revealed that it is a flintlock .44 caliber 6 shot revolver, when he used it to shoot down Corazon.