Double Action, Single Action and Double Action Only In regards to pistols if the hammer is down for a single action pistol then the hammer must be cocked before firing. Will a double action pistol by pulling on the trigger the hammer will be cocked and will fire the cartridge. The return of the slide cock the hammer requiring a lighter trigger pull for subsequent shots. A double action only pistol the hammer will not recock when it is fired
Blow back pistols
In terms of ease of manufacture and cost, this is least expensive method of making a handgun today. There are many quality blowback semiautomatic pistols on the market and many more that are not so good.
Blow back pistols rely on the weight of the slide and the recoil spring to keep the action closed until the bullet leaves the barrel. In general blow back pistols are chambered for rimfire and relatively low powered centerfire cartridges such as the 380 automatic or 9mm Makarov. There are however, a few manufacturers that make pistols chambered for the 9 mm luger or 45 ACP and do so by making an extraordinarily heavy slide with a powerful recoil spring which makes for a cumbersome and generally unreliable pistol.
The barrel and the slide are locked together when the action is closed. When the pistol is fired the barrel and slide travel back a short distance on the receiver where the barrel disengages and the momentum of the slide causes it to continue back extracting the cartridge case from the chamber and ejecting it from the pistol. The slide continues back, compressing the recoil spring and recocking the pistol until it reaches its limit of travel. The recoil spring pushes the slide forward, which strips a cartridge from the magazine and shoves it into the chamber. The barrel and the slide are once again locked together and the pistol is ready to fire again.
Uncommon used with handguns chambered for rifle or some large magnum pistol cartridges .
Have 4 to 9 chambers in a cylinder, which rotates within the gun. Most commonly with 6 chambers
Double Action Revolvers
Most modern double action revolvers made have a swing out crane on which the cylinder rides. Cartridge cases are removed with the aid a star extractor in the center of the cylinder. The are however some older top break revolvers. Most are chambered for 22 rimfire or some of the lower powered revolver cartridges such as 32 S&W and 38 S&W.
Single Action Revolvers
A single action revolver requires that the hammer to be pulled back to rotate the cylinder and cock the firearm. The original colt revolvers and some replicas have a sharp cone like protrusion on the face of the hammer that acts as the firing pin. Firearms of this type must be carried with the hammer on an empty chamber to prevent an accidental discharge in case the hammer is bumped. A good example of a revolver of this type is the Colt Peacemaker.
Single shot pistols
Most common are the single shot break open pistols such as the Thompson Center Contender or the Remington bolt action XP-100 pistol. These generally fire more powerful cartridges and are used for hunting and long range target shooting at silhouetes.
Double Action Revolvers
Basic Function of common revolver
Cylinder on colt revolvers rotates clockwise, S&W, Ruger, Taurus rotates counter clockwise
Opening a Colt Double Action Revolver
Gripping the gun in the right hand use your thumb to move cylinder latch backwards and with your left hand reach under the gun and use your fingers to push the cylinder from right to left.
Opening a Smith & Wesson, Taurus or Rossi Double Action Revolver
Gripping the gun in the right hand use your thumb to push the cylinder latch forwards and with your left hand reach under the gun and use your fingers to push the cylinder from right to left.
Opening a Ruger Double Action Revolver
gripping the gun in the right hand use your thumb to depress the cylinder latch and with your left hand reach under the gun and use your fingers to push the cylinder from right to left.