A revolver is a multishot firearm, usually a handgun, in which multiple firing chambers are grouped into a cylinder which rotates to align each round sequentially with a single barrel.

History
A revolver works by having several firing chambers arranged in a circle in a cylindrical block that are brought into alignment with the firing mechanism and barrel one at a time. A single action revolver requires the hammer to be pulled back by hand before each shot. In contrast, in a double action revolver, squeezing the trigger can pull back the hammer to cock the gun as well as serving to release the hammer. Most modern double action revolvers can also be fired in single action mode as well, which serves to improve the practical accuracy by reducing the force and distance required to pull the trigger. A few designs, however, have fully-concealed hammers and are double-action-only. Because the effort required to cock the hammer is part of the firing action in double action revolvers, they can generally be fired faster than a single action, but at the cost of reduced accuracy in the hands of most shooters.
Most commonly, such guns have a six or eight shot capacity (hence the other name Six Shooter); however, some revolvers have up to a 10-shot capacity (this often depends on the caliber, though different companies produce revolvers in the same calibers with different capacities, due to other design differences), and each chamber has to be reloaded manually. This makes the procedure of reloading such a weapon slow. The alternatives are a replaceable cylinder, a speedloader (manufactured by HKS and Safariland) which can reload all chambers at once, or a moon clip that holds a full load (or even half of one in the case of a half-moon clip) of ammunition and that is inserted along with the ammunition. Additionally, Bianchi manufactures a product known as a "speedstrip". Speedstrips cannot reload a completely empty revolver as rapidly as a speedloader, but are less expensive, flatter, and more flexible when it comes to partial reloads.
Compared to autoloading handguns, a revolver is often simpler to operate (despite often being more mechanically complex) and may have greater reliability (depending on factors such as firmness of grip, ammunition used, and degree of maintenance and lubrication provided to the firearm). For example, should a semiautomatic pistol fail to fire, clearing the chamber requires manually cycling the action to remove the errant round, as cycling the action normally depends on the energy of a cartridge firing. With a revolver, this is not necessary as none of the energy for cycling the revolver comes from the firing of the cartridge, but is supplied by the user either through cocking the hammer or, in a double action design, by just squeezing the trigger.
Over the long period of development of the revolver, many calibers have been used. Some of these have proved more durable during periods of standardization and some have entered general public awareness. Among these are the .22 rimfire, a popular target shooting caliber; .38 Special and .357 Magnum, known for police use; the .44 Magnum, famous from Clint Eastwood's "Dirty Harry" films; and the .45 Long Colt, used in the Colt revolver of the "Wild West". Introduced in 2003, the Smith & Wesson Model 500 is the most powerful production revolver ever created, using the .500 S&W Magnum round.
As revolvers are of a 19th-century design, it is not surprising that semi-automatic pistols have overtaken them in military and law enforcement applications. Their often lower ammunition capacities and relatively longer reload times compared to autoloading pistols are the main reasons for the switchover that occurred in the 1980s and 1990s. Additionally, the flat profile of semi-automatics make them more suitable for concealed carry. Revolvers still remain popular in the role of back-up (and possibly off-duty) guns among American law enforcement officers and security guards. Also, revolvers are still common in the American private sector as defensive and sporting/hunting firearms.
Famous police and military revolvers include the Webley, the Colt Single Action Army, the Smith & Wesson Model 29, the Smith & Wesson Model 10, and the Smith & Wesson 1917.
Revolver technology does live on in other weapons used by the military. Some autocannons and grenade launchers use mechanisms similar to revolvers, and some riot shotguns use spring loaded cylinders holding up to 12 rounds.

Overview

Loading and unloading
The first revolvers were muzzle loading, which meant that each chamber in the cylinder was loaded from the front with loose powder and a bullet. Usually, there was a loading lever attached to the bottom of the barrel that gave the user leverage to force the oversized lead ball into the chamber, which sealed it and held the ball and powder securely in place. The first practical revolvers were caplocks, because the caplock method of priming was the first to be compact enough to make a practical revolver feasible.

Muzzle loading
The first generation of cartridge revolvers were converted caplock designs.
Since the cylinder in these revolvers is firmly attached at the front and rear of the frame, and since the frame is typically full thickness all the way around, fixed cylinder revolvers are inherently strong designs. Because of this, many modern large caliber hunting revolvers tend to be based on the fixed cylinder design.

Fixed cylinder designs
The next method used for loading and unloading cartridge revolvers was the top break design. In a top break revolver, the frame is hinged at the bottom front of the cylinder. Releasing the lock and pushing the barrel down brings the cylinder up - this exposes the rear of the cylinder for reloading. In most top break revolvers, the act of pivoting the barrel and cylinder operates an extractor that pushes the cartridges in the chambers back far enough that they will fall free, or can be removed easily. Fresh rounds are then placed into the cylinder, either one at a time or all at once with either a speedloader or a moon clip. The barrel and cylinder are then rotated back and locked in place, and the revolver is ready to fire. Since the frame is in two parts, held together by a latch on the top rear of the cylinder, top break revolvers are relatively weak, and cannot handle high pressure rounds. Top break designs are nearly extinct in the world of firearms, but they are still found in airguns.
One of the most famous "break top" revolvers is the Schofield Model 3, designed in the late 19th century and used by western outlaw Jesse James. Another notable design is the Enfield and Webley series of revolvers used by the British Armed Forces from the 1880s through the 1960s.

Top break
The last and most common method of loading and unloading is the swing out cylinder. The cylinder is mounted on a pivot that is coaxial with the chambers, and the cylinder swings out and down (to the left in most cases, due to right-handed shooters being in the majority). An extractor is fitted, operated by a rod projecting from the front of the cylinder assembly. When pressed, it will push all fired rounds free simultaneously (as in top break models, the travel is designed to not completely extract longer, unfired rounds). The cylinder may then be loaded, singly or again with a speedloader, and closed, where it latches in place. The pivoting part that supports the cylinder is called the crane; it is the weak point of swing-out cylinder designs. Using the method often portrayed in movies and television of flipping the cylinder open and closed with a flick of the wrist will in fact cause the crane to bend, throwing the cylinder out of alignment with the barrel. Lack of alignment between chamber and barrel is a dangerous condition- impeding the bullet's transition from chamber to barrel. This gives rise to higher pressures in the chamber, bullet damage, and the potential for an explosion if the bullet becomes stuck. The shock of firing can also put a great deal of stress on the crane, as in most designs the cylinder is only held closed at one point, the rear of the cylinder. Stronger designs, such as the Ruger Super Redhawk, use a lock in the crane as well as the lock at the rear of the cylinder. This latch provides a more secure bond between cylinder and frame, and allows the use of larger, more powerful cartridges.

Swing out cylinder

Action
In a single action revolver, the hammer is manually cocked, usually with the thumb of the firing or supporting hand. This action advances the cylinder to the next round and locks the cylinder in place with the chamber aligned with the barrel. The trigger, when pulled, releases the hammer, which fires the round in the chamber. To fire again, the hammer must be manually cocked again. This is called "single action" because the trigger only performs a single action, of releasing the hammer. Because only a single action is performed and trigger pull is lightened, firing a revolver in this way allows most shooters to achieve greater accuracy.

Single action
Most double action revolvers may be fired in two ways. The first way is exactly the same as a single action revolver; the hammer is cocked, which advances the cylinder clockwise when viewed from the rear, and when the trigger is pulled, this releases the hammer. Double action revolvers also can be fired from a hammer down position, by just pulling the trigger. In this case, the trigger first cocks the hammer (thus advancing the cylinder counterclockwise or clockwise, depending on the gun's manufacturer) and then releases the hammer at the rear of its travel, firing the round in the chamber. Certain revolvers, called double action only, lack the latch that enables the hammer to be locked to the rear, and thus can only be fired in the double action mode. With no way to lock the hammer back, double action only designs tend to have bobbed or spurless hammers, and may even have the hammer completely covered by the revolver's frame. These are generally intended for concealed carry for defensive purposes, where a hammer spur could snag when the revolver is drawn. The potential reduction in accuracy in aimed fire is offset by the increased usability for concealed carry.

Double action
As a general rule, revolvers cannot be equipped with a sound suppressor, as there is usually a small gap that exists between the revolving cylinder and the barrel over which a bullet must traverse or jump when fired. From this opening, a rather loud report is produced even when a suppressor is installed on the end of the barrel of most revolvers. However, eliminating this problem would make the revolver an ideal weapon for suppressed use: in automatics, the action itself creates a significant amount of noise even if muzzle report is totally eliminated. A revolver, which does not cycle on its own and whose action is naturally quiet, does not present this problem.
Nonetheless, a suppressible revolver design does exist in the Nagant M1895, a Russian military revolver used from 1895 through World War II. This revolver uses a unique cartridge that extends beyond the end of the bullet, and a cylinder that moves forward to place the end of the cartridge inside the barrel when ready to fire. This bridges the gap between the cylinder and the barrel, and expands to seal the gap when fired. While the tiny gap between cylinder and barrel on most revolvers is insignificant to the internal ballistics, the seal is especially effective when used with a suppressor, and a number of suppressed Nagant revolvers have been used since its invention. which uses ammunition that incorporates the silencing mechanism into the cartridge case, making the gap between cylinder and barrel irrelevant as far the suppression issue is concerned. Ironically the OTs-38 does need an unusually close and precise fit between the cylinder and barrel due to the shape of bullet in the special ammunition (Soviet SP-4), which was originally designed for use in a semi-automatic.

Use with suppressors

Main article: Automatic revolver Famous brands and manufacturers

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