Single-action and Double-action Firearms
The terms single-action and double-action refer to the mechanism of ammunition cycling in a firearm. With a single-action weapon the shooter must physically cock the hammer back before pulling the trigger to initiate the cartridge. You may be most familiar with them as the cowboy “six-shooter” although the number of chambers in the cylinder can vary widely. Semi-automatic pistols can also be single action, at least for the first round.
The Colt model 1911 is one of the most popular single action semi-autos. The hammer must be cocked to fire the first round. After that the gases produced by the cartridge firing will cycle the weapon and load a new cartridge from the magazine.
With double-action firearms each pull of the trigger will either cock the hammer and rotate the cylinder (in revolvers), or release the hammer or striker (semi-automatics). With semi-automatic firearms the gasses produced by the discharge of the cartridge will force the slide rearward while extracting and ejecting the spent cartridge. When the slide moves forward it strips a new cartridge from the magazine and loads it.
As a writer it’s important to understand the distinction between the two. For instance, if you have a scene where your protagonist is in a gunfight and during that fight he/she cocks the hammer of the gun (for dramatic effect I suppose) make sure it is a single action weapon. For that matter make sure it has a hammer. Most American law enforcement agencies will not allow single action weapons to be carried by their officers. So if your character is an officer keep that in mind.
Posted on May 9, 2011, in General and tagged crime, Crime Scene, csi, detective, double-action, fiction, firearms, forensics, gun, mystery, pistol, police, revolver, single-action, thriller, tom adair. Bookmark the permalink. Leave a Comment.