To remove the cylinder, open it and slide it forward. Certain contemporary revolvers, primarily DA types like the Smith & Wesson 686 shown, contain a hammer block. When the side plate is removed, the hammer block falls out as an internal safety device. Remove the hammer block from the cannon and lay it aside with the other components.
The hammer block serves to protect the user's hand from being hit by the hammer if the gun goes off while it is in his or her grasp. The block also prevents the hammer from coming down on its own if the gun is dropped or otherwise mishandled. Modern guns without hammer blocks use trigger protection devices instead. The hammer block must be struck with the heel of your hand to release it; this is known as "hammering the block." Once released, it will fall away into the barrel chamber. There it will stay until fired, at which time it will be returned to its blocking position.
Hammer blocks are used on many large-frame revolvers to provide protection for the shooter. Most often, they are found on double-action (DA) guns where the possibility of fire when handling the weapon during play or practice is possible. On these guns, removal of the hammer block allows them to be safely handled. They can then be placed back on the gun when finished shooting.
Some single-action (SA) guns have hammer blocks for the same reason as stated above.
Locked revolvers have a tiny keyhole above the cylinder release clasp. Owners may lock the action of the revolver using a key provided with the purchase of every new revolver, presumably keeping it "secure" against use by minors or other unauthorized individuals. The key is small enough to fit into a pocket, and can be carried by any authorized user of the firearm.
Locked revolvers were popular among law enforcement officers in the early 20th century. By locking their guns away from children and others who might try to open them with gunpowder charges, officers could prevent accidental shootings while on duty.
Today, locked revolvers are used primarily for security purposes, to protect valuable equipment or collectibles that cannot be left unattended. They are also useful when you do not want your gun to go off accidentally.
The majority of today's revolvers are designed to be operated by one single manual crank or push button. A few older models still include a second set of barrels, called "delayed blowback", which require two separate actions to fire: a pull of the trigger and then a pressure point below the trigger guard. These features are used to provide security against someone trying to force the gun to fire through physical manipulation of the weapon itself.
Locked revolvers function by placing a special tool into the firing pin hole.
The hammer of a single-action revolver is manually cocked, generally with the thumb of the firing or supporting hand. This movement moves the cylinder to the next round and secures the cylinder with the chamber aligned with the barrel. The trigger is then pulled, which rotates the hammer into position for firing.
A double-action revolver has a two-step process to fire each cartridge. First, the hammer is manually cocked. Then, the trigger is pulled, which simultaneously releases the cylinder latch and triggers the hammer to strike the firing pin. The second step is required because some of the energy from the trigger pull is used to release the latch instead of just triggering the hammer. This allows for a stronger trigger pull without causing the gun to fire when you accidentally bump it.
A single-action revolver can be fired only by pulling the trigger; there is no separate latch to release in order to fire the gun. As soon as the trigger is pulled, the hammer falls onto the firing pin to discharge the weapon.
Revolvers usually have an internal mechanism that prevents the gun from being fired if it is dropped with the hammer down. This is called "lockout". This is done to prevent children from playing with the guns or animals from being shot by accident.