A revolver is a type of handgun that has a revolving cylinder containing multiple chambers for cartridges and a barrel for firing them. Each time the trigger is pulled, the cylinder advances to the next chamber and the round is fired. Depending on caliber, most revolvers have a capacity of anywhere from 5 to 10 rounds of ammunition. Once all rounds are expended, the cylinder can be flipped open to extract the spent casings and insert new ammunition.