A revolver (also called a wheel gun ^[1][2]) is a repeating handgun that has a revolving cylinder containing multiple chambers and at least one barrel for firing. The revolver allows the user to fire multiple rounds without reloading after every shot, unlike older single-shot firearms. After a round is fired the hammer is cocked and the next chamber in the cylinder is aligned with the barrel by the shooter either manually pulling the hammer back (single action operation) or by rearward movement of the trigger (double action operation).

Revolvers still remain popular as back-up and off-duty handguns among American law enforcement officers and security guards and are still common in the American private sector as defensive and sporting/hunting firearms. Famous and iconic revolvers models include the Colt 1851 Navy Revolver, the Webley, the Colt Single Action Army, the Colt Official Police, Smith & Wesson Model 10, the Smith & Wesson Model 29 of Dirty Harry fame, the Nagant M1895, and the Colt Python.

Though revolvers are usually referred to as and often are handguns, other firearms may also have a revolver action. These include some models of grenade launchers, shotguns, rifles and cannons, such as revolver cannon. These are different from other firearms with revolving chambers, such as Gatling-style rotary cannons in that revolvers typically require the hammer to be re-cocked with each shot and require manual reloading, while guns like the Minigun are motor-driven and have a barrel for each chamber.

In the development of firearms, an important limiting factor was the time it took to reload the weapon after it was fired. While the user was reloading, the weapon was useless, and an adversary might be able to take advantage of the situation and kill or wound the user. Several approaches to the problem of increasing the rate of fire were developed, the earliest simply being multi-barrelled weapons which allowed two or more shots without reloading.^[3] Later weapons featured multiple barrels revolving along a single axis.

During the late 16th century in China, Zhao Shi-zhen invented the Xun Lei Chong, a five-barreled musket revolver spear. Around the same time, the earliest examples of what today is called a revolver were made in Germany. These weapons featured a single barrel with a revolving cylinder holding the powder and ball. They would soon be made by many European gun-makers, in numerous designs and configurations.^[4] However, these weapons were difficult to use, complicated and prohibitively expensive to make, and as such they were not widely distributed.

In 1836, an American, Samuel Colt, patented the mechanism which led to the widespread use of the revolver,^[5] the mechanically indexing cylinder. According to Samuel Colt, he came up with the idea for the revolver while at sea, inspired by the capstan, which had a ratchet and pawl mechanism on it, a version of which was used in his guns to rotate the cylinder by cocking the hammer. This provided a reliable and repeatable way to index each round and did away with the need to manually rotate the cylinder. Revolvers proliferated largely due to Colt's ability as a salesman. But his influence spread in other ways as well; the build quality of his company's guns became famous, and its armories in America and England trained several seminal generations of toolmakers and other machinists, who had great influence in other manufacturing efforts of the next half century.^[6]

Early revolvers were caplocks and loaded as a muzzle-loader: the user poured black powder into each chamber, rammed down a bullet on top of it, then placed percussion caps on the nipple at the rear of each chamber, where the hammer would fall on it. This was similar to loading a traditional single-shot muzzle-loading pistol, except that the powder and shot could be loaded directly into the front of the cylinder rather than having to be loaded down the whole length of the barrel. Importantly, this allowed the barrel itself to be rifled, since the user wasn't required to force the tight fitting bullet down the barrel in order to load it (a traditional muzzle-loading pistol had a smoothbore and relatively loose fitting shot, which allowed easy loading, but gave much less accuracy). When firing the next shot, the user would raise his pistol vertically as he cocked the hammer back so as to let the fragments of the burst percussion cap fall out so as to not jam the mechanism. Some of the most popular cap-and-ball revolvers were the Colt Model 1851 "Navy" Model, 1860 "Army" Model, and Colt Pocket Percussion revolvers, all of which saw extensive use in the American Civil War. Although American revolvers were the most common, European arms makers were making numerous revolvers by that time as well, many of which found their way into the hands of the American forces, including the single action Lefaucheux and LeMat revolver and the Beaumont–Adams and Tranter revolvers, which were early double-action weapons, in spite of being muzzle-loaders.^[7]

In 1854, Eugene Lefaucheux introduced the Lefaucheux Model 1854, the first revolver to use self-contained metallic cartridges rather than loose powder, pistol ball, and percussion caps. It is a single-action, pinfire revolver holding six rounds.^[8]

On November 17, 1856, Daniel B. Wesson and Horace Smith signed an agreement for the exclusive use of the Rollin White Patent at a rate of 25 cents for every revolver. Smith & Wesson began production late in 1857 and enjoyed years of exclusive production of rear-loading cartridge revolvers in America, due to their association with Rollin White, who held the patent^[9] and vigorously defended it against any perceived infringement by other manufacturers (much as Colt had done with his original patent on the revolver). Although White held the patent, other manufacturers were able to sell firearms using the design, provided they were willing to pay royalties.^[10]Flayderman's%20Guide%20to%20An]]^{[[11]](https://openlibrary.org/search?q=Jinks%2C%20Roy%20G.%3B%20Sandra%20C.%20Krein%20%282006%29.%20} [[CITE|11|https://openlibrary.org/search?q=Jinks%2C%20Roy%20G.%3B%20Sandra%20C.%20Krein%20%282006%29.%20*Smith%20%26%20We)

After White's patent expired in April 1869, a 3rd extension was refused.

Other gun-makers were then allowed to produce their own weapons using the rear-loading method, without having to pay a royalty on each gun sold.

Early guns were often conversions of earlier cap-and-ball revolvers, modified to accept metallic cartridges loaded from the rear, but later models, such as the Colt Model 1872 "Open Top" and the Smith & Wesson Model 3, were designed from the start as cartridge revolvers.^[10]

In 1873, Colt introduced the famous Model 1873, also known as the Single Action Army, the "Colt.45" (not to be confused with Colt-made models of the M1911 semi-automatic) or simply, "the Peacemaker", one of the most famous handguns ever made.^[12] This popular design, which was a culmination of many of the advances introduced in earlier weapons, fired 6 metallic cartridges and was offered in over 30 different calibers and various barrel lengths. It is still in production, along with numerous clones and lookalikes, and its overall appearance has remained the same since 1873. Although originally made for the United States Army, the Model 1873 was widely distributed and popular with civilians, ranchers, lawmen, and outlaws alike. Its design has influenced countless other revolvers. Colt has discontinued its production twice, but brought it back due to popular demand and continues to make it to this day.

In the U.S. the traditional single-action revolver still reigned supreme until the late 19th century.

In Europe, however, arms makers were quick to adopt the double-action trigger.

While the US was producing weapons like the Model 1873, the Europeans were building double-action models like the French MAS Modèle 1873 and the somewhat later British Enfield Mk I and II revolvers (Britain relied on cartridge conversions of the earlier Beaumont–Adams double-action prior to this). Colt's first attempt at a double action revolver to compete with the European manufacturers was the Colt Model 1877, which earned lasting notoriety for its overly complex, expensive and fragile trigger mechanism, which in addition to failing frequently, also had a terrible trigger pull unless given the attentions of a competent gunsmith.

In 1889, Colt introduced the Model 1889, the first truly modern double action revolver, which differed from earlier double action revolvers by having a "swing-out" cylinder, as opposed to a "top-break" or "side-loading" cylinder. Swing out cylinders quickly caught on, because they combined the best features of earlier designs. Top-break actions gave the ability to eject all empty shells simultaneously, and exposed all chambers for easy reloading, but having the frame hinged into two halves weakened the gun and negatively affected accuracy, due to lack of rigidity. "Side-loaders", like the earlier Colt Model 1871 and 1873, gave a rigid frame, but required the user to eject and load one chamber at a time, as they rotated the cylinder to line each chamber up with the side-mounted loading gate.^[13] Smith & Wesson followed 7 years later with the ''Hand Ejector, Model 1896'' in .32 S&W Long caliber, followed by the very similar, yet improved, Model 1899 (later known as the Model 10), which introduced the new.38 Special cartridge. The Model 10 went on to become the best selling handgun of the 20th century, at 6,000,000 units, and the .38 Special is still the most popular chambering for revolvers in the world. These new guns were an improvement over the Colt 1889 design since they incorporated a combined center-pin and ejector rod to lock the cylinder in position. The 1889 did not use a center pin and the cylinder was prone to move out of alignment.^[13]

Revolvers have remained popular to the present day in many areas, although in the military and law enforcement, they have largely been supplanted by magazine-fed semi-automatic pistols such as the Beretta M9, especially in circumstances where reload time and higher cartridge capacity are deemed important.^[14]

Elisha Collier of Boston, Massachusetts patented a flintlock revolver in Britain in 1818, and significant numbers were being produced in London by 1822.^[15] The origination of this invention is in doubt, as similar designs were patented in the same year by Artemus Wheeler in the United States and by Cornelius Coolidge in France.^[16] Samuel Colt submitted a British patent for his revolver in 1835 and an American patent (number 138) on February 25, 1836 for a Revolving gun, and made the first production model on March 5 of that year.^[17]

Another revolver patent was issued to Samuel Colt on August 29, 1839.

The February 25, 1836 patent was then reissued as U.S.

Patent RE00,124 ^[69] entitled Revolving gun on October 24, 1848. This was followed by U.S. Patent 0,007,613 ^[70] on September 3, 1850 for a Revolver, and by U.S. Patent 0,007,629 ^[71] on September 10, 1850 for a Revolver. U.S. Patent 5,333,531 ^[72] was issued to Roger C. Field for an economical device for minimizing the flash gap of a revolver between the barrel and the cylinder. In 1855, Rollin White patented the bored-through cylinder entitled Improvement in revolving fire-arms U.S. Patent 00,093,653 ^[73]. In 1856 Horace Smith & Daniel Wesson formed a partnership (S&W), developed and manufactured a revolver chambered for a self-contained metallic cartridge.^[18]

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.

In contrast, other repeating firearms, such as bolt-action, lever-action, pump-action, and semi-automatic, have a single firing chamber and a mechanism to load and extract cartridges into it.^[19]

A single-action revolver requires the hammer to be pulled back by hand before each shot, which also revolves the cylinder.

This leaves the trigger with just one "single action" left to perform - releasing the hammer to fire the shot - so the force and distance required to pull the trigger can be minimal.

In contrast, with a self-cocking revolver, one long squeeze of the trigger pulls back the hammer and revolves the cylinder, then finally fires the shot.

They can generally be fired faster than a single-action, but with reduced accuracy in the hands of most shooters.^[19]

Most modern revolvers are "traditional double-action", which means they may operate either in single-action or self-cocking mode.

The accepted meaning of "double-action" has, confusingly, come to be the same as "self-cocking", so modern revolvers that cannot be pre-cocked are called "double-action-only".^[19] These are intended for concealed carry, because the hammer of a traditional design is prone to snagging on clothes when drawn.

Most revolvers do not come with accessory rails, which are used for mounting lights and lasers, except for the Smith & Wesson M&P R8 (.357 Magnum),^[20] Smith & Wesson Model 325 Thunder Ranch (.45 ACP),^[21] and all versions of the Chiappa Rhino (.357 Magnum, 9×19mm, .40 S&W, or 9×21mm) except for the 2" model, respectively.^[22] However, certain revolvers, such as the Taurus Judge and Charter Arms revolvers, can be fitted with accessory rails.^[23]

Most commonly, such revolvers have 5 or 6 chambers, hence the common names of "six-gun" or "six-shooter".^[24] However, some revolvers have 7, 8, 9, or 10 chambers,^[24] often depending on the caliber, and at least one revolver has 12 chambers (the US Fire Arms Model 12/22).^[25] Each chamber has to be reloaded manually, which makes reloading a revolver a much slower procedure than reloading a semi-automatic pistol.^[24]

Compared to autoloading handguns, a revolver is often much simpler to operate and may have greater reliability.^[24] 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.^[24] 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.^[24] Another significant advantage of revolvers is superior ergonomics, particularly for users with small hands.^[24] A revolver's grip does not hold a magazine, and it can be designed or customized much more than the grip of a typical semi-automatic.^[24] Partially because of these reasons, revolvers still hold significant market share as concealed carry and home-defense weapons.^[24]

A revolver can be kept loaded and ready to fire without fatiguing any springs and is not very dependent on lubrication for proper firing.^[24] Additionally, in the case of double-action-only revolvers there is no risk of accidental discharge from dropping alone, as the hammer is cocked by the trigger pull.^[24] However, the revolver's clockwork-like internal parts are relatively delicate and can become misaligned after a severe impact, and its revolving cylinder can become jammed by excessive dirt or debris.^[24]

Over the long period of development of the revolver, many calibers have been used.^[26] 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 caliber popular for target shooting and teaching novice shooters; .38 Special and .357 Magnum, known for police use; the .44 Magnum, famous from Clint Eastwood's "Dirty Harry" films; and the .45 Colt, used in the Colt revolver of the Wild West. Introduced in 2003, the Smith & Wesson Model 500 is one of the most powerful revolvers, utilizing the .500 S&W Magnum cartridge.^[27]

Because the rounds in a revolver are headspaced on the rim, some revolvers are capable of chambering more than one type of ammunition. The.44 Magnum round will chamber the shorter.44 Special and shorter .44 Colt, likewise the.357 Magnum will safely chamber.38 Special and .38 Short Colt. In 1996 a revolver known as the Medusa M47 was made that could chamber 25 different cartridges with bullet diameters between.355" and.357".^[28]

Revolver technology lives 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.^[29] In addition to serving as backup guns, revolvers still fill the specialized niche role as a shield gun; law enforcement personnel using a "bulletproof" gun shield sometimes opt for a revolver instead of a self-loading pistol, because the slide of a pistol may strike the front of the shield when fired. Revolvers do not suffer from this disadvantage. A second revolver may be secured behind the shield to provide a quick means of continuity of fire. Many police also still use revolvers as their duty weapon due to their relative mechanical simplicity and user friendliness.^[30]

With the advancement of technology and design in 2010 major revolver manufacturers are coming out with polymer frame revolvers like the Ruger LCR, Smith & Wesson Bodyguard 38, and Taurus Protector Polymer. The new innovative design incorporates advanced polymer technology that lowers weight significantly, helps absorbs recoil, and strong enough to handle.38 Special +P and .357 Magnum loads. The polymer is only used on the lower frame and joined to a metal alloy upper frame, barrel, and cylinder. Polymer technology is considered one of the major advancements in revolver history because the frame has always been metal alloy and mostly one piece frame design.^[31]

Another recent development in revolver technology is the Rhino, a revolver introduced by Italian manufacturer Chiappa in 2009 and first sold in the U.S. in 2010. The Rhino, built with the U.S. concealed carry market in mind, is designed so that the bullet fires from the bottom chamber of the cylinder instead of the top chamber as in standard revolvers. This is intended to reduce muzzle flip, allowing for faster and more accurate repeat shots. In addition, the cylinder cross-section is hexagonal instead of circular, further reducing the weapon's profile.^[22]

The first revolvers were front loading (also referred to as muzzleloading), and were a bit like muskets in that the powder and bullet were loaded separately. These were caplocks or "cap and ball" revolvers, because the caplock method of priming was the first to be compact enough to make a practical revolver feasible. When loading, each chamber in the cylinder was rotated out of line with the barrel, and charged from the front with loose powder and an oversized bullet. Next, the chamber was aligned with the ramming lever underneath the barrel. Pulling the lever would drive a rammer into the chamber, pushing the ball securely in place. Finally, the user would place percussion caps on the nipples on the rear face of the cylinder.^[7]

After each shot, a user was advised to raise his revolver vertically while cocking back the hammer so as to allow the fragments of the spent percussion cap to fall out safely.

Otherwise, the fragments could fall into the revolver's mechanism and jam it.

Caplock revolvers were vulnerable to "chain fires", wherein hot gas from a shot ignited the powder in the other chambers.

This could be prevented by sealing the chambers with cotton, wax, or grease.^[32]

Loading a cylinder in this manner was a slow and awkward process and generally could not be done in the midst of battle.^[33] Some soldiers solved this by carrying multiple revolvers in the field.

Another solution was to use a revolver with a detachable cylinder design.

These revolvers allowed the shooter to quickly remove a cylinder and replace it with a full one.^[19]

In many of the first generation of cartridge revolvers (especially those that were converted after manufacture), the base pin on which the cylinder revolved was removed, and the cylinder taken from the revolver for loading.

Most revolvers using this method of loading are single-action revolvers, although Iver Johnson produced double-action models with removable cylinders. The removable-cylinder design is employed in some modern "micro-revolvers" (usually in .22 caliber), in order to simplify their design. These weapons are small enough to fit in the palm of the hand.^[31]

Later single-action revolver models with a fixed cylinder used a loading gate at the rear of the cylinder that allowed insertion of one cartridge at a time for loading, while a rod under the barrel could be pressed rearward to eject the fired case.^[34]

The loading gate on the original Colt designs (and on nearly all single-action revolvers since, such as the famous Colt Single Action Army) is on the right side, which was done to facilitate loading while on horseback; with the revolver held in the left hand with the reins of the horse, the cartridges can be ejected and loaded with the right hand.^[35]

Because the cylinders in these types of revolvers are firmly attached at the front and rear of the frame, and the frame is typically full thickness all the way around, fixed cylinder revolvers are inherently strong designs.

Accordingly, many modern large caliber hunting revolvers tend to be based on the fixed cylinder design.

Fixed cylinder revolvers can fire the strongest and most powerful cartridges, but at the price of being the slowest to load and reload and they cannot use speedloaders or moon clips for loading, as only one chamber is exposed at a time to the loading gate.^[36]

In a top-break revolver, the frame is hinged at the bottom front of the cylinder. Releasing the lock and pushing the barrel down exposes the rear face of the cylinder. In most top-break revolvers, this act also 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 inserted into the cylinder. The barrel and cylinder are then rotated back and locked in place, and the revolver is ready to fire.^[19]

Top break revolvers can be loaded more rapidly than fixed-frame revolvers, especially with the aid of a speedloader or moon clip. However, this design is much weaker and cannot handle high pressure rounds. While this design is mostly obsolete today, supplanted by the stronger yet equally convenient swing-out design, manufacturers have begun making reproductions of late 19th century designs for use in cowboy action shooting.^[19]

The most commonly found top-break revolvers were manufactured by Smith & Wesson, Webley & Scott, Iver Johnson, Harrington & Richardson, Manhattan Fire Arms, Meriden Arms and Forehand & Wadsworth.^[37]

The tip-up was the first revolver design for use with metallic cartridges in the Smith & Wesson Model 1, on which the barrel pivoted upwards, hinged on the forward end of the topstrap. On the S & W tip-up revolvers, the barrel release catch is located on both sides of the frame in front of the trigger. Smith & Wesson discontinued it in the third series of the Smith & Wesson Model 1 1/2 but it was fairly widely used in Europe in the 19th century, after a patent by Spirlet in 1870, which also included an ejector.^[38]

The most modern method of loading and unloading a revolver is by means of the swing out cylinder.^[39] The cylinder is mounted on a pivot that is parallel to the chambers, and the cylinder swings out and down (to the left in most cases). 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, closed, and latched in place.^[19]

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 can in fact cause the crane to bend over time, throwing the cylinder out of alignment with the barrel.

Lack of alignment between chamber and barrel is a dangerous condition, as it can impede 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.^[40]

The shock of firing can exert 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 cylinders are rather strong, but not as strong as fixed cylinders, and great care must be taken with the cylinder when loading, so as not to damage the crane.^[40]

One unique design was designed by Merwin Hulbert in which the barrel and cylinder assembly were rotated 90° and pulled forward to eject shells from the cylinder.

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.

Additionally, the need to cock the hammer manually acts as a safety.

Unfortunately with some revolvers, since the hammer rests on the primer or nipple, accidental discharge from impact is more likely if all 6 chambers are loaded.

The Colt Paterson Revolver, the Walker Colt, the Colt's Dragoon and the Colt Single Action Army pistol of the American Frontier era are all good examples of this system.^[19]

In double-action (DA), the stroke of the trigger pull generates two actions:

Thus, DA means that a cocking action separate from the trigger pull is unnecessary; every trigger pull will result in a complete cycle.

This allows uncocked carry, while also allowing draw-and-fire using only the trigger.

A longer and harder trigger stroke is the trade-off.

However, this drawback can also be viewed as a safety feature, as the gun is safer against accidental discharges from being dropped.^[19]

Most double-action revolvers may be fired in two ways.^[19]

Certain revolvers, called double-action-only (DAO) or, more correctly but less commonly, self-cocking, 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, DAO designs tend to have bobbed or spurless hammers, and may even have the hammer completely covered by the revolver's frame (i.e., shrouded or hooded). These are generally intended for concealed carrying, where a hammer spur could snag when the revolver is drawn. The potential reduction in accuracy in aimed fire is offset by the increased capability for concealment.^[41]

DA and DAO revolvers were the standard-issue sidearm of countless police departments for many decades.

Only in the 1980s and 1990s did the semiautomatic pistol begin to make serious inroads after the advent of safe actions. The reasons for these choices are the modes of carry and use. Double action is good for high-stress situations because it allows a mode of carry in which "draw and pull the trigger" is the only requirement—no safety catch release nor separate cocking stroke is required.^[41]

In the cap-and-ball days of the mid 19th century, two revolver models, the English Tranter and the American Savage "Figure Eight", used a method whereby the hammer was cocked by the shooter’s middle finger pulling on a second trigger below the main trigger.

Iver Johnson made an unusual model from 1940 to 1947, called the Trigger Cocking Double Action. If the hammer was down, pulling the trigger would cock the hammer. If the trigger was pulled with the hammer cocked, it would then fire. This meant that to fire the revolver from a hammer down state, the trigger must be pulled twice.^[42]

The Zig zag revolver is a 3D printed.38 Revolver made public in May 2014.^[43][44][44] It was created by a $500 3D-printer using plastic filament, but the name of the printer was not revealed by the creator.^[44] It was created by a Japanese citizen from Kawasaki named Yoshitomo Imura^[44] He was arrested in May 2014 after he had posted a video online of himself firing a 3D printed Zig Zag revolver.^[43] It is the first 3D printed Japanese gun in the world which can discharge live cartridges.^[44]

As a general rule, revolvers cannot be effective with a sound suppressor ("silencer"), as there is usually a small gap between the revolving cylinder and the barrel which a bullet must traverse or jump when fired. From this opening, a rather loud report is produced. A suppressor can only suppress noise coming from the muzzle.^[45]

A suppressible revolver design does exist in the Nagant M1895, a Belgian designed revolver used by Imperial Russia and later the Soviet Union from 1895 through World War II. This revolver uses a unique cartridge whose case extends beyond the tip 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.^[46]

There is a modern revolver of Russian design, the OTs-38,^[47] which uses ammunition that incorporates the silencing mechanism into the cartridge case, making the gap between cylinder and barrel irrelevant as far as the suppression issue is concerned. 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.

Additionally, the US Military experimented with designing a special version of the Smith & Wesson Model 29 for Tunnel Rats, called the Quiet Special Purpose Revolver or QSPR. Using special.40 caliber ammunition, it never entered official service.^[48]

The term "automatic revolver" has two different meanings, the first being used in the late nineteenth and early twentieth centuries when "automatic" referred not to the operational mechanism of firing, but of extraction and ejection of spent casings.

An "automatic revolver" in this context is one which extracts empty fired cases "automatically," i.e., upon breaking open the action, rather than requiring manual extraction of each case individually with a sliding rod or pin (as in the Colt Single Action Army design).

This term was widely used in the advertising of the period as a way to distinguish such revolvers from the far more common rod-extraction types.^[49]

In the second sense, "automatic revolver" refers to the mechanism of firing rather than extraction.

Double-action revolvers use a long trigger pull to cock the hammer, thus negating the need to manually cock the hammer between shots.

The disadvantage of this is that the long, heavy pull cocking the hammer makes the double-action revolver much harder to shoot accurately than a single-action revolver (although cocking the hammer of a double-action reduces the length and weight of the trigger pull).

A rare class of revolvers, called automatic for its firing design, attempts to overcome this restriction, giving the high speed of a double-action with the trigger effort of a single-action.

The Webley-Fosbery Automatic Revolver is the most famous commercial example. It was recoil-operated, and the cylinder and barrel recoiled backwards to cock the hammer and revolve the cylinder. Cam grooves were milled on the outside of the cylinder to provide a means of advancing to the next chamber—half a turn as the cylinder moved back, and half a turn as it moved forward..38 caliber versions held eight shots,.455 caliber versions six. At the time, the few available automatic pistols were larger, less reliable, and more expensive. The automatic revolver was popular when it first came out, but was quickly superseded by the creation of reliable, inexpensive semi-automatic pistols.^[50]

In 1997, the Mateba company developed a type of recoil-operated automatic revolver, commercially named the Mateba Autorevolver, which uses the recoil energy to auto-rotate a normal revolver cylinder holding six or seven cartridges, depending on the model. The company has made several versions of its Autorevolver, including longer-barrelled and carbine variations, chambered for .357 Magnum, .44 Magnum and .454 Casull.^[51]

The Pancor Jackhammer is a combat shotgun based on a similar mechanism to an automatic revolver. It uses a blow-forward action to move the barrel forward (which unlocks it from the cylinder) and then rotate the cylinder and cock the hammer.^[52]

Revolvers were not limited to handguns and as a longer barrelled arm is more useful in military applications than a sidearm, the idea was applied to both rifles and shotguns throughout the history of the revolver mechanism with mixed degrees of success.^[53]

Revolving rifles were an attempt to increase the rate of fire of rifles by combining them with the revolving firing mechanism that had been developed earlier for revolving pistols.

Colt began experimenting with revolving rifles in the early 19th century, making them in a variety of calibers and barrel lengths.

Colt revolving rifles were the first repeating rifles adopted by the U.S. Government, but they had their problems. They were officially given to soldiers because of their rate of fire. But after firing six shots, the shooter had to take an excessive amount of time to reload. Also, on occasion Colt rifles discharged all their rounds at once, endangering the shooter. Even so, an early model was used in the Seminole Wars in 1838.^[54][55] During the Civil War a LeMat Carbine was made based on the LeMat revolver.^[56]

Colt briefly manufactured several revolving shotguns that were met with mixed success. The Colt Model 1839 Shotgun was manufactured between 1839 and 1841. Later, the Colt Model 1855 Shotgun, based on the Model 1855 revolving rifle, was manufactured between 1860 and 1863. Because of their low production numbers and age they are among the rarest of all Colt firearms.^[57]

The Armsel Striker was a modern take on the revolving shotgun that held 10 rounds of 12 Gauge ammunition in its cylinder. It was copied by Cobray as the Streetsweeper.^[14][58]

Taurus manufactures a carbine variant of the Taurus Judge revolver along with its Australian partner company, Rossi known as the Taurus/Rossi Circuit Judge. It comes in the original combination chambering of .410 bore and .45 Long Colt, as well as the .44 Remington Magnum chambering. The rifle has small blast shields attached to the cylinder to protect the shooter from hot gases escaping between the cylinder and barrel.^[59]

The MTs255 (Russian: МЦ255) is a shotgun fed by a 5-round internal revolving cylinder. It is produced by the TsKIB SOO, Central Design and Research Bureau of Sporting and Hunting Arms. They are available in 12, 20, 28 and 32 gauges, and .410 bore.

The Hawk MM-1, Milkor MGL, RG-6, and RGP-40 are grenade launchers that use a revolver action. Because the cylinders are much more massive, they use a spring-wound mechanism to index the cylinder.

Revolver cannons use a motor-driven revolver-like mechanism to fire.

A six gun is a revolver that holds six cartridges. The cylinder in a six gun is often called a "wheel", and the six gun is itself often called a "wheel gun".^[60][61] Although a "six gun" can refer to any six-chambered revolver, it is typically a reference to the Colt Single Action Army, or its modern look-alikes such as the Ruger Vaquero and Beretta Stampede.

Until the 1970s, when older-design revolvers such as the Colt Single Action Army and Ruger Blackhawk were re-engineered with drop safeties (such as firing pin blocks, hammer blocks, or transfer bars) that prevent the firing pin from contacting the cartridge's primer unless the trigger is pulled, safe carry required the hammer being positioned over an empty chamber, reducing the available cartridges from six to five, or, on some models, in between chambers on either a pin or in a groove for that purpose, thus keeping the full six rounds available. This kept the uncocked hammer from resting directly on the primer of a cartridge. If not used in this manner, the hammer rests directly on a primer and unintentional firing may occur if the gun is dropped or the hammer is struck. Some holster makers provided a thick leather thong to place underneath the hammer that both allowed the carry of a gun fully loaded with all six rounds and secured the gun in the holster to help prevent its accidental loss.

Six guns are used commonly by single-action shooting enthusiasts in shooting competitions, designed to mimic the gunfights of the Old West, and for general target shooting, hunting and personal defense.^[62]