The word "pistol" is often synonymous with the word "handgun". Some handgun experts make a technical distinction that views pistols as a subset of handguns. Sometimes in American usage, the term "pistol" refers to a handgun whose chamber is integral with the barrel, making pistols distinct from the other main type of handgun, the revolver, which has a revolving cylinder containing multiple chambers. However, Commonwealth usage makes no distinction at a technical level—"pistol" may refer to revolvers, semi-automatics, or muzzle-loading/cap-&-ball handguns. For example, the official designation of the Webley Mk VI was "Pistol, Revolver, Webley No. 1 Mk VI", and the designation "Pistol No. 2 Mk I" was used to refer to both the Enfield Revolver and the later Browning Hi-Power semi-automatic.
The first pistols were made as early as the 15th century, but their creator is unknown. By the 18th century, the term came to be used often to refer to handheld firearms. Practical revolver designs appeared in the 19th century, and it was in that century that the (sometimes-observed) technical differentiation in usage from the words "pistol" and "revolver" developed, at that time differentiating the newer revolver from the single-shot pistols previously in use.
 Etymology of "pistol"
Hand cannon from the Chinese Yuan Dynasty (1271–1368).The word "pistol" is derived from the French pistole (or pistolet), which has these possible origins:
From the Czech pistole and this one from the Czech píšťala (flute or pipe, referring to the shape of a Hussite firearm), from Middle High German pischulle or from Middle French pistole.
From the city of Pistoia, Italy, where hand-held guns (designed to be fired from horseback) were first produced in the 1540s.
That early pistols were carried by cavalry in holsters hung from the pommel (or pistallo in medieval French) of a horse's saddle. Single-shot pistols are theoretically the simplest pistols. The earliest handguns were single-shot, muzzle-loading guns with ignition provided by inserting a smoldering match cord into a touch hole. As such, they were essentially nothing more than miniature cannons, small enough to be handheld.
Improvements followed in subsequent centuries, as various types of locks (ignition devices) were invented. In the matchlock, the separate match cord was affixed to a spring-loaded pivot which could be tripped by a trigger. In the wheellock, a mechanism analogous to that used in today's cigarette lighters replaced the smoldering match cord. In the 17th century, the flintlock, which strikes a flint against steel, appeared. (The flintlock, amazingly, remained state-of-the-art for some two hundred years.) In the 19th century, percussion caps were developed, followed shortly by modern integrated-primer cartridges, and hammers therefore traded their flint for firing pins.
Single-shot pistols continue to be manufactured today and are often used for target shooting and handgun hunting game, including big game. The most powerful handguns are capable of taking all game including elephant.
Not long after the very beginning of firearms, inventors began experimenting with multi-barreled weapons in the quest for the ability to fire more than one shot before needing to reload. Not surprisingly, all types of firearms were included in their efforts, from volley guns to analogously devised handguns. Before anyone had developed a practical capability for delivering multiple loads to one barrel in quick succession (which is how repeating fire is usually accomplished today), gun smiths were aggregating multiple loaded barrels into one place.
Some examples of multi-barreled pistols are:
Pepper-box guns (variously referred to as pepper-box pistols or pepper-box revolvers)
Howdah pistols, often made from double-barrelled rifles.
With the development of the revolver in the 19th century, gunsmiths had finally achieved the goal of a practical capability for delivering multiple loads to one handgun barrel in quick succession. Revolvers feed ammunition via the rotation of a cartridge-filled cylinder, in which each cartridge is contained in its own ignition chamber, and is sequentially brought into alignment with the weapon's barrel by a mechanism linked to the weapon's trigger (double-action) or its hammer (single-action). These nominally cylindrical chambers, usually numbering between five and eight depending on the size of the revolver and the size of the cartridge being fired, are bored through the cylinder so that their axes are parallel to the cylinder's axis of rotation; thus, as the cylinder rotates, the chambers revolve about the cylinder's axis.
There is a hybrid form of the revolver, known as the automatic revolver, which combines the revolving chamber concept of the conventional revolver with the recoil-harnessing, self-cycling ability of the semi-automatic pistol. Weapons of this type are rare, as the technology was quickly rendered obsolete by a combination of the double-action revolver and the semi-automatic pistol.
The first lever action pistols were based on a Horace Smith and Daniel B. Wesson patent of 1854. The Smith & Wesson pistols were made in Norwich, Connecticut 1854-55. In 1855, Oliver F. Winchester became an active investor and H. Smith and D.B. Wesson both dropped out of the enterprise. In July 1855, the name was changed to Volcanic Repeating Arms Company, and later to New Haven Arms Company, opening an important chapter in Winchester's history. The production of the Volcanic pistols lasted until 1860. Two models were produced: The Navy Pistol .41 cal. with 6" / 8" / 16 " barrels and a Pocket Pistol .31 cal. with 3½" / 6" barrels.
The next development in handgun history after a practical revolver was the development of the semi-automatic pistol, which uses the energy of one shot to reload the chamber for the next. Typically recoil energy from a fired round is mechanically harnessed; however, larger calibers may also be gas operated (e.g. Desert Eagle). After a round is fired, the pistol will cycle, ejecting the spent casing and chambering a new round from the magazine, allowing another shot to take place immediately.
Some terms that have been, or still are, used as synonyms for "semi-automatic pistol" are automatic pistol, autopistol, autoloader, self-loading pistol and selfloader.A machine pistol is generally defined as a firearm designed to be fired with one hand, and capable of fully automatic or selective fire. While there are a number of machine pistols such as the Glock 18 and later models of the Mauser C96, these are rare; the light weight, small size, and extremely rapid rates of fire of a machine pistol make them difficult to control, making the larger and heavier submachine gun a better choice in cases where the small size of a machine pistol is not needed. Most machine pistols can attach a shoulder stock (the Heckler & Koch VP70 would only fire single rounds at a time unless the stock was attached); others, such as the Beretta 93R, add a forward handgrip. Either of these additions technically create a legal non-pistol under the US National Firearms Act, as pistols are by definition designed to be fired with one hand. The addition of a stock or forward handgrip is considered a design change that creates either a short-barreled rifle or any other weapon, and therefore such additions are generally only found on legal machine guns.
Single-action handguns have a trigger whose sole function is to drop a pre-cocked hammer to discharge a cartridge. For revolvers, the popular Colt Peacemaker of Old West fame is typically thought of. Its hammer must be manually cocked for each shot. For auto-loading pistols the Colt 1911 or Browning Hi-Power are typical examples. They must be cocked for the first shot, but subsequent shots are cocked automatically due to the racking of the slide. These types of guns typically have a very light and crisp trigger pull, making for more accurate target shooting.
Traditional double-action handguns have a mechanism that can be either pre-cocked, like the above single-action gun, or can be fired with the gun uncocked. In this case, the gun has an additional mechanism added to the trigger that will cock the gun (and rotate the cylinder in the case of revolvers) as the trigger is pulled. Once the trigger is pulled far enough, the hammer is released and the gun fired. For autoloading pistols the self-loading mechanism will also re-cock the hammer after the first shot is fired so that subsequent shots are fired single-action. For revolvers, each shot is fired with the hammer initially uncocked unless the shooter manually cocked the gun. Popular auto pistols in this category include the Walther P38 and Beretta 92. These guns typically have a longer, heavier trigger pull for the first shot then light, crisp pulls for subsequent shots. Popular revolvers include the Ruger Redhawk and Smith & Wesson Model 29. These have comparatively long, heavy trigger pulls for all shots unless the revolver is manually cocked.
Double-action only handguns do not have the ability to be cocked and is usually evidenced by a lack of either the hammer spur or the entire hammer. A typical autopistol in this category is the Ruger KP93DAO and a typical revolver is the Smith & Wesson Centennial or the Enfield No 2 Mk I*. All pistols in this category have a long, heavy trigger pull for all shots.
Pre-set triggers are only on autoloading pistols. In this case the pistol mechanism is always partially cocked while being carried and during firing. The partially cocked firing pin or striker is not cocked enough to cause an accidental release to discharge a cartridge, adding to the safeness of the design, but is cocked enough to remove much of the trigger pull and weight of a purely double-action pistol. These types of pistols do not have external hammers and do not generally have a decock function. Common pistols in the category are the HS2000 (Springfield XD) and the various forms of the extremely popular Glock. The trigger pull of these guns is between double-action and single-action pistols. Pre-set triggers may or may not have a second-strike feature on a dud cartridge.
Some automatic pistol models such as the HK USP Universal Self-loading Pistol (or U.S.P.) come in a variety of mechanism types and can be easily changed by a gunsmith for both left- and right-handed shooters and for different operating mechanism and safety features.
Glock introduced a new "Safe Action" mechanism that is neither a single nor double action. The weapon is never "cocked" in terms of a hammer being "cocked". The partly tensioned firing pin lock is released by pressing the trigger, resulting in the first and subsequent trigger pulls all being the same.