Gun barrel in the context of Cordite

Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, charcoal (which is mostly carbon), and potassium nitrate (saltpeter). The sulfur and charcoal act as fuels, while the saltpeter is an oxidizer. Gunpowder has been widely used as a propellant in firearms, artillery, rocketry, and pyrotechnics, including use as a blasting agent for explosives in quarrying, mining, building pipelines, tunnels, and roads.

Gunpowder is classified as a low explosive because of its relatively slow decomposition rate, low ignition temperature and consequently low brisance (breaking/shattering). Low explosives deflagrate—burning at subsonic speeds—whereas high explosives detonate, producing a supersonic shockwave. Ignition of gunpowder packed behind a projectile generates enough pressure to force the shot from the muzzle at high speed, but usually not enough force to rupture the gun barrel. It thus makes a good propellant but is less suitable for shattering rock or fortifications with its low-yield explosive power. Nonetheless, it was widely used to fill fused artillery shells (and used in mining and civil engineering projects) until the second half of the 19th century, when the first high explosives were put into use.

A muzzleloader is any firearm in which the user loads the projectile and the propellant charge into the muzzle end of the gun (i.e., from the forward, open end of the gun's barrel). This is distinct from the modern designs of breech-loading firearms, in which user loads the ammunition into the breech end of the barrel. The term "muzzleloader" applies to both rifled and smoothbore type muzzleloaders, and may also refer to the marksman who specializes in the shooting of such firearms. The firing methods, paraphernalia and mechanism further divide both categories as do caliber (from cannons to small-caliber palm guns).

Modern muzzleloading firearms range from reproductions of sidelock, flintlock and percussion long guns, to in-line rifles that use modern inventions such as a closed breech, sealed primer and fast rifling to allow for considerable accuracy at long ranges.

A firearm is any type of gun that shoots projectiles using high explosive pressure generated from combustion (deflagration) of chemical propellant, most often black powder in antique firearms and smokeless powder in modern firearms. Small arms is a subset of light firearms that is designed to be readily carried and operated by an individual. The term "firearm" is however variably defined in both technically and legally in different countries (see legal definitions), and can be used colloquially (sometimes incorrectly) to refer to any type of guns.

The first firearms originated in 10th-century Song dynasty China (see gunpowder weapons in the Song dynasty), when bamboo tubes containing gunpowder and pellet projectiles were mounted on spears to make the portable fire lance, which was operable by a single person and was later used effectively as a shock weapon in the siege of De'an in 1132. In the 13th century, fire lance barrels were replaced with metal tubes and transformed into the metal-barreled hand cannon, and the technology gradually spread throughout Eurasia during the 14th century. Older firearms typically used black powder as a propellant, but modern firearms use smokeless powder or other explosive propellants. Most modern firearms (with the notable exception of smoothbore shotguns) have rifled barrels to impart a stabilizing spin to the bullet for improved external ballistics.

A bayonet (from Old French bayonette, now spelt baïonnette) is a knife, dagger, sword, or spike-shaped melee weapon designed to be mounted on the end of the barrel of a rifle, carbine, musket or similar long firearm, allowing the gun to be used as an improvised spear in close combat.

The term is derived from the town of Bayonne in southwestern France, where bayonets were supposedly first used by Basques in the 17th century. From the early 17th to the early 20th century, it was an infantry melee weapon used for both offensive and defensive tactics, usually when charging in mass formations (human wave attacks). In contemporary times, bayonets are considered a weapon of last resort, and are rarely used in combat, although they are still used for ceremonial purposes (e.g, military parades).

A pistol is a type of handgun, characterized by a barrel with an integral chamber. The word "pistol" derives from the Middle French pistolet (c. 1550), meaning a small gun or knife, and first appeared in the English language c. 1570 when early handguns were produced in Europe. In colloquial usage, the word "pistol" is often used as a generic term to describe any type of handgun, inclusive of revolvers (which have a single barrel and a separate cylinder housing multiple chambers) and the pocket-sized derringers (which are often multi-barrelled).

The most common type of pistol used in the contemporary era is the semi-automatic pistol. The older single-shot and lever-action pistols are now rarely seen and used primarily for nostalgic hunting and historical reenactment. Fully-automatic machine pistols are uncommon in civilian usage because of their generally poor recoil-controllability (due to the lack of a buttstock) and strict laws and regulations governing their manufacture and sale (where they are regarded as submachine gun equivalents).

A shotgun (also known as a scattergun, peppergun, or historically as a fowling piece) is a long-barreled firearm designed to shoot a straight-walled cartridge known as a shotshell, which discharges numerous small spherical projectiles called shot, or a single solid projectile called a slug. Shotguns are most commonly used as smoothbore firearms, meaning that their gun barrels have no rifling on the inner wall, but rifled barrels for shooting sabot slugs (slug barrels) are also available.

Shotguns come in a wide variety of calibers and gauges ranging from 5.5 mm (.22 inch) to up to 5 cm (2.0 in), though the 12-gauge (18.53 mm or 0.729 in) and 20-gauge (15.63 mm or 0.615 in) bores are by far the most common. Almost all are breechloading, and can be single barreled, double barreled, or in the form of a combination gun. Like rifles, shotguns also come in a range of different action types, both single-shot and repeating. For non-repeating designs, over-and-under and side-by-side break action shotguns are by far the most common variants. Although revolving shotguns do exist, most modern repeating shotguns are either pump action or semi-automatic, and also fully automatic, lever-action, or bolt-action to a lesser extent.

A carbine (/ˈkɑːrbiːn/ KAR-been or /ˈkɑːrbaɪn/ KAR-byn) is a long gun that has a barrel shortened from its original length. Most modern carbines are rifles that are compact versions of a longer rifle or are rifles chambered for less powerful cartridges.

The smaller size and lighter weight of carbines make them easier to handle. They are typically issued to high-mobility troops such as special operations soldiers and paratroopers, as well as to mounted, artillery, logistics, or other non-infantry personnel whose roles do not require full-sized rifles, although there is a growing tendency for carbines to be issued to front-line soldiers to offset the increasing weight of other issued equipment. An example of this is the M4 carbine, the standard issue carbine of the United States Armed Forces.

Ballistics is the field of mechanics concerned with the launching, flight behaviour and impact effects of projectiles, especially weapon munitions such as bullets, unguided bombs, rockets and the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.

A ballistic body is a free-moving body with momentum, which can be subject to forces such as those exerted by pressurized gases from a gun barrel or a propelling nozzle, normal force by rifling, and gravity and air drag during flight.

A gun is a device that propels a projectile using pressure or explosive force. The projectiles are typically solid, but can also be pressurized liquid (e.g. in water guns or cannons), or gas (e.g. light-gas gun). Solid projectiles may be free-flying (as with bullets and artillery shells) or tethered (as with Tasers, spearguns and harpoon guns). A large-caliber gun is also called a cannon. Guns were designed as weapons for military use, and then found use in hunting. Now, there are guns, e.g., toy guns, water guns, paintball guns, etc., for many purposes.

The means of projectile propulsion vary according to designs, but are traditionally effected pneumatically by a high gas pressure contained within a barrel tube (gun barrel), produced either through the rapid exothermic combustion of propellants (as with firearms), or by mechanical compression (as with air guns). The high-pressure gas is introduced behind the projectile, pushing and accelerating it down the length of the tube, imparting sufficient launch velocity to sustain its further travel towards the target once the propelling gas ceases acting upon it after it exits the muzzle. Alternatively, new-concept linear motor weapons may employ an electromagnetic field to achieve acceleration, in which case the barrel may be substituted by guide rails (as in railguns) or wrapped with magnetic coils (as in coilguns).

In machining, boring is the process of enlarging a hole that has already been drilled (or cast) by means of a single-point cutting tool (or of a boring head containing several such tools), such as in boring a gun barrel or an engine cylinder. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. Boring can be viewed as the internal-diameter counterpart to turning, which cuts external diameters.

There are various types of boring. The boring bar may be supported on both ends (which only works if the existing hole is a through hole), or it may be supported at one end (which works for both, through holes and blind holes). Lineboring (line boring, line-boring) implies the former. Backboring (back boring, back-boring) is the process of reaching through an existing hole and then boring on the "back" side of the workpiece (relative to the machine headstock).

A bullet is a kinetic projectile, a component of firearm ammunition that is shot from a gun barrel. They are made of a variety of materials, such as copper, lead, steel, polymer, rubber and even wax; and are made in various shapes and constructions (depending on the intended applications), including specialized functions such as hunting, target shooting, training, and combat. Bullets are often tapered, making them more aerodynamic. Bullet size is expressed by weight and diameter (referred to as "caliber") in both imperial and metric measurement systems. Bullets do not normally contain explosives but strike or damage the intended target by transferring kinetic energy upon impact and penetration.

A breechloader is a firearm or artillery piece in which the user loads the ammunition from the breech (rear) end of the barrel. The vast majority of modern firearms are breech-loaders.

Before the mid-19th century, most guns were muzzleloaders, guns loaded from the muzzle (front) end of the barrel.

The chamber of a firearm is the cavity at the back end of a breechloading weapon's barrel or cylinder, where the ammunition is inserted before being fired. The rear opening of the chamber is the breech, and is sealed by the breechblock or the bolt.

The percussion cap, percussion primer, or caplock, introduced in the early 1820s, is a type of single-use percussion ignition device for muzzle loader firearm locks enabling them to fire reliably in any weather condition. Its invention gave rise to the caplock mechanism or percussion lock system which used percussion caps struck by the hammer to set off the gunpowder charge in rifles and cap and ball firearms. Any firearm using a caplock mechanism is a percussion gun. Any long gun with a cap-lock mechanism and rifled barrel is a percussion rifle. Cap and ball describes cap-lock firearms discharging a single bore-diameter spherical bullet with each shot.

A touch hole, also known as a cannon vent, is a small hole at the rear (breech) portion of the barrel of a muzzleloading gun or cannon. The hole provides external access of an ignition spark into the breech chamber of the barrel (where the combustion of the propellant occurs), either with a slow match (matchlock), a linstock or a flash pan ignited by some type of pyrite- (wheellock) or flint-based gunlock (snaplock, snaphaunce, and flintlock), which will initiate the combustion of the main gunpowder charge. Without a touch hole, it would be nearly impossible to ignite the powder because the only otherwise access into the barrel is from the front via the muzzle, which is obturated by the projectile.

In the later caplock firearms, the ignition sparks are generated by a shock-sensitive percussion cap placed over a conical "nipple", which has a hollow conduit known as the flash channel, that leads into the barrel and serves the same function as the touch hole.