Gun Glossary: Small Arms Content from the guide to life, the universe and everything

Gun Glossary: Small Arms

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A collection of Bren Guns.

Guns represent a long evolution in mankind's pursuit of effective ways to end lives. Make no mistake, the gun was initially designed to kill, pure and simple, though a number of sports and non-lethal recreational activities have since evolved and involved them. All modern variations of the firearm evolved from black powder weapons such as the harquebus1 and hand cannons found in the late 13th Century. Despite various differences in mechanical design, projectile, purpose, and appearance, all guns share a common denominator. They are designed to, at the wielder's behest, propel an object through a tube at a target.

There are many misgivings surrounding these weapons the world over. Subsequently, different countries and cultures have adopted very different attitudes and laws regarding them.

Although long-range and heavier weapons, such as cannon and other artillery pieces, are often known as 'guns'2, this Entry deals exclusively with small arms.

Small Arms

Small arms are weapons that can be carried by an individual, normally a member of the armed forces. This usually includes pistols, rifles, shot guns, light machine guns, sub-machine guns, assault rifles and carbines. Older weapons, such as the musket, can also be described as being small arms.

Locks and Actions

Locks and actions describe how the different types of gun are fired and loaded.

  • Touchlock

    The oldest method of firing a gun and used by almost all cannon until the Crimean War. The very earliest small arms, such as harquebusses, were touchlock. These guns do not have triggers. Instead the gun is fired by touching the pan or touch-hole, which contains a small amount of powder, with a match. This ignites the powder in the barrel and fires the gun.

  • Matchlock

    The first guns with triggers, the action was taken from the crossbow. Matchlocks were very similar to a touch lock, with the trigger mechanism linked to a lit match cord, usually hemp cord soaked in saltpetre. Pulling the trigger moves the match cord into contact with the pan, firing the gun.

  • Wheel-lock

    The wheel-lock worked to the same principle as modern cigarette lighters. After the wheel is wound up, pulling the trigger rotated the wheel and created sparks that ignited the powder in the pan. More expensive than matchlocks, wheel-locks were often used as pistols by the wealthy for hunting rather than the battlefield.

  • Flintlock

    Flintlocks were efficient, reliable, easy to use and the most common form of firing a gun until the Crimean War. Pulling the trigger caused the flint in the hammer to create a spark which ignited the powder in the pan and fired the gun.

  • Caplock

    Also known as the Percussion Lock, the percussion cap was invented in 1805 by Reverend Alexander John Forsyth. He wished to reduce the delay in firing caused by pulling the trigger, igniting the powder in the pan and the gun actually firing. The percussion lock removed the pan containing powder and instead a cap is placed onto a nipple behind the barrel. When the trigger is pulled, the hammer explodes the cap which ignites the powder and fires the gun. Caplocks were virtually waterproof and later, when the cap was placed within the bottom of the cartridge, effectively led to the development of all modern weapons.

  • Breech-Loader

    Gun which is loaded by opening the breech, or rear, of the barrel.

  • Muzzle-Loader

    Any gun loaded from its front (muzzle).

  • Smooth-Bore

    Gun that has not been rifled.

  • Bolt-Action

    Many rifles require the bolt to be manually rotated, pulled to the rear, then moved forward again in order to eject spent brass, advance a round and move the next round into the chamber. This was common throughout the 20th Century including both World Wars where the bolt action Lee Enfield rifle was the standard British weapon.

  • Lever-action

    Similar to the bolt-action, empty cartridges are ejected by pulling a lever located behind the trigger mechanism. Easier to operate than a bolt-action, but often less accurate. Lever-actions are popular in Westerns and are epitomised by the Winchester Repeating Rifle, although the Martini-Henry lever-action rifle was used from the late Victorian era up to the Great War, including in the Anglo-Zulu War.

  • Pump-Action

    Weapons that require the pumping mechanism to load and unload ammunition are considered to be pump-action. Most pump-action weapons are shotguns, which have an internal magazine which feeds a new shell into the chamber each time the gun is pumped.

  • Single Action

    Single Action weapons must be manually cocked for each shot, that is, the hammer must be drawn back in order to spin the revolver cylinder around and position the next round in front of the hammer. Pulling the trigger has the single action of releasing the hammer. This improves accuracy but slows the fire rate.

    For semi-automatic pistols, Single Action means that the pistol must be manually cocked for the first shot (usually, this is done by pulling the 'slide' - this action cocks the hammer and feeds a cartridge into the chamber). For the second, and all consecutive shots, cocking is often done automatically in pistols, when recoil force pulls back the slide.

  • Double Action

    Double Action for the revolver means that trigger pull both cocks and releases the hammer for each shot, doing double the work than a Single Action weapon, which just releases the hammer. This action also rotates the cylinder to the next position. This mode speeds up the firing rate and simplifies shooting actions, but greatly increases trigger pull from the 2.2-4.4 lbs (1-2 kg) usually found in single-actions, to 8.8-12.2 lbs (4-6 kg) in double-actions, which can affect accuracy. For semi-automatic pistols, double action means that only the first round must be manually fed into the chamber; all following rounds are fed automatically and the hammer re-cocked with each shot.

  • Automatic Pistols

    Automatic pistols, not to be confused with machine pistols, have the simple expedient of not requiring cocking between rounds. The force generated in firing is sufficient to push the slide back, eject the spent brass, and allow a new round to be loaded.

  • Semi-Automatic

    Any weapon which does not require reloading, hand-chambering, or re-cocking between expended rounds is considered semi-automatic. One round is expended each time the trigger is pulled.

  • Full-Automatic

    By holding down the trigger mechanism, the weapon will discharge ammunition continuously until either the magazine/belt is emptied or there is a mechanical failure with the weapon.

Types of Firearms

A collection of guns.


The term pistol describes a firearm that can be held, cocked, and fired effectively in one hand. Although matchlock, flintlock, wheel lock and cap lock pistols have all been used and were largely single-shot, most modern pistols are either 'semi-automatic', chamber-fed by a detachable magazine, or 'revolver', with rounds pre-chambered in a rotating cylinder3. Pistols typically, though not always, weigh less than five pounds and are perhaps most effective at short range, such as 30 feet (10 metres) or less, although competitive target shooting often have targets at 25 and 50 yards (23 and 46 metres). They are often less powerful and not as accurate as their rifle equivalents.

Machine Pistols

Machine pistols are pistols which, by virtue of their design, will continue to expend ammunition at a high rate as long as the trigger is depressed. Essentially small submachine guns that can be fired in one hand, they are far more popular in the world of film and television than in reality due to their inaccuracy.


A blunderbuss is the muzzle-loading forerunner of the shot gun, typically used to fire a large number of metal balls or shot rather than a single bullet. With a large bore4 and short barrel, often with a flared end like a trumpet to help with loading, especially on horseback, and to spread the trajectory of the shot.


Shotguns were originally designed as hunting weapons. A shotgun is closely related to a rifle, with a few subtle differences. Breech-loading shotguns, the most primitive style of the weapon, are loaded by opening a latched hinge where the barrel meets the stock and trigger. A 'shell', a special shotgun round, is inserted directly into the chamber, the breech is closed, and the trigger strikes the back of the shell. Pump-action shotguns have an internal cylinder magazine. Both styles of shotguns are typically 'smooth bore'. By drawing back on the 'pump' mechanism, spent shell casings are ejected and a new one is advanced into place. Both styles of shotgun fire either 'shot' or 'sabot' rounds, which will be covered later in this Entry.


A harquebus, also known as an arquebus, was a primitive gun used in the 15th to 17th Centuries. The first shoulder-weapons with a wooden stock, they were very similar to a musket but shorter and wider. Having a larger calibre they generally fired a heavier bullet but were loaded and fired in a similar manner to the musket. They were touchlock or matchlock weapons and often were aimed with the support of a forked rest.


A musket is a historic smooth bore, muzzle-loading gun common between the 16th and 19th Centuries. Not as accurate as rifles, from the Napoleonic Wars onwards muskets were gradually replaced by rifles. By the time of the Napoleonic War, to load a musket involved a complicated process. Gunpowder was kept in a special paper container known as the cartridge, which also held the spherical ball to be shot at the enemy. Some of the powder would be added to the priming pan, the rest poured down the muzzle. The ball would be dropped into the barrel, followed by the paper cartridge to prevent the ball and powder from falling out. They would be rammed down the barrel into place with a ram rod to the breech. When the gun was fired, a spark in the priming pan would ignite the powder there and in the barrel, propelling the ball out of the musket at great speed. Before breech-loading guns became available, muskets were quicker to load than rifles, with well-drilled troops capable of 4-5 rounds per minute rather than a rifleman's 2 or 3. Among the most famous muskets is the Brown Bess.


Rifles, originally called the rifled musket, represent the heavier end of the firearm spectrum. Rifles come in three forms; single-shot, semi-automatic and manual-action. Single-shot rifles need to be reloaded after every shot. Semi-automatic rifles are magazine or clip fed, with each pull of the trigger discharging a round, ejecting the spent brass, and feeding a new round into the chamber. Semi-automatic rifles are usually the least accurate as the automatic action causes vibrations when the trigger is pulled, affecting the firing of the gun.

Manual-action rifles require the shooter to operate a mechanism by hand before they can fire again. Bolt-actions are the most common, but pump-action and lever-action use different mechanism to achieve the same effect. Lever-action rifles are typically faster firing than bolt rifles, but less accurate.


A carbine is in essence a short rifle. These were originally used by cavalry on horseback where a full-sized rifle would have been impractical. An early type of wheel-lock carbine commonly used by the cavalry was known as a dragon; those armed with it were known as dragoons.

Assault Rifles

Assault rifles as discussed here are a type of rifle designed for combat use, especially in close-combat military situations. Assault rifles differ from civilian rifles in several aspects. Generally speaking, assault rifles are weapons capable of selective fire with a large capacity detachable magazine and firing a cartridge that is either shorter or of lesser calibre than a main battle rifle, making them lighter and easier to carry. As 'select fire' weapons, they can switch between firing single shots, short bursts, usually 3 rounds for each pull on the trigger, or fully automatic fire. In combat they are normally used in single-shot mode, as full-auto fire is less accurate, and merely allows you to miss faster.

The first assault rifle was the German StG 445 and the most famous worldwide is the AK-47, also known as the Kalashnikov, first developed in 1947. Other examples include the Colt M-16 and SA-80.

'Assault Weapons' is a term used in American law to describe self-loading semi-automatic rifles that look like assault rifles, but aren't.

Sub-machine Guns

Although at first glance sub-machine guns, often abbreviated to SMGs, can be seen to bridge the gap between assault rifles and machine pistols and appear a hybrid of the two, in terms of development history, submachine guns were developed for trench fighting and other situations where traditional rifles were too long and too slow-firing to be useful. Sub-machine guns were found to be too weak and short-range for most combat situations. Designed to be fired with both hands, they have a fully automatic rate of fire and are fed by magazines. They are typically more accurate than machine pistols, but have less impact than a rifle of the same calibre.

Machine Guns

Machine guns can be described as essentially rifles designed to fire on a fully-automatic basis, although that is an over-simplification. There are various differences in design and use between rifles and machine guns and types of machine guns themselves. Though they can be used effectively on a semi-automatic setting, they are most effective in laying down fire upon a large sector, either as a defensive device or in support of an advance, whereas rifles are ideally used for single, precise shots.

Machine guns are usually fed by 'belts' of ammunition, though magazine-fed machine guns are not uncommon. Early examples of machine gun include the Gatling Gun (1861), Maxim6 (in service 1885-1918) and Vickers (in service in the British Army 1912-1968). The machine gun reached its dominance during the Great War.

In the present day, light machine guns are designed for use by one, sometimes two soldiers, perhaps the most famous of which is the Bren Gun (used by the British army 1935-1991). These are often magazine-fed. Medium machine guns use full-bore cartridges, are usually belt-fed and usually require a tripod or rest. Heavy machine guns are usually intended to provide greater impact and damage to enemy vehicles, including aircraft, and buildings. Even heavier weapons built on machine gun principles are termed 'automatic cannons'7 or 'autocannons' rather than machine guns.

Pieces and Parts

A reenactment of a historical military scene.

Nearly all firearms share certain common factors. Knowing the terminology associated with these factors will make it not only easier to converse about firearms, but understand the differences in design and the relative effectiveness of a weapon.

  • Round (Cartridge and Bullet)

    Although originally the cartridge referred to the paper container that held the shot and a small quantity of gunpowder, with more modern weapons a cartridge normally consists of the blasting cap at the back, the bullet at the front held together by a normally brass cylindrical case8. When the blasting cap is struck by the hammer of the weapon, normally in the centre of the cartridge, it causes the powder within to rapidly combust. The resulting expansion of gas forces the bullet out of the barrel at great speed. The mass of a bullet is weighed in grains. A standard M-16 bullet is approximately 62 grains (4 grams), while a .50 (12.7mm) calibre bullet, the largest man-portable round, is nearly 671 grains (43.5 grams).

  • Calibre

    Calibre is the byword among all firearms for measuring guns. Calibre measures the diameter of a bullet and is generally given in inches. Calibre tends to vary between countries, manufacturers, and weapons. A .303 calibre round is 0.303 inches in diameter. When considering more technically accurate dimensions of a round, the SI definition is more useful. A .303 calibre round is described as 7.7 × 56mm, or a bullet 7.7mm in diameter set inside of a cartridge measuring 56mm in length.

  • Gauge and Bore

    Shotgun shells are a special kind of ammunition fired in only those weapons. The calibre of shotguns is measured in terms of gauge or bore. The gauge number is determined by the number of solid spheres of a diameter equal to the inside diameter of the barrel that could be made from a pound of lead. So a 10 gauge shotgun has an inside diameter equal to that of a sphere made from one-tenth of a pound (43.4g) of lead. The higher the gauge number, the smaller the diameter of the barrel. Common gauges are 10, 12, 16, and 20. Bore is measured in the same manner as calibre but is typically only used in association with the smallest popular shotgun, the .410 bore, which has a barrel with an inside diameter of 0.410 inches (10.414 mm). It is often mistakenly referred to as a .410 gauge.

  • Shotgun Shells:

    Shotguns fire one of three basic rounds for hunting, combat, and sport purposes: Slugs, Shotshells (commonly known simply as 'shot'), and Buckshot.

    • Slugs

      The heaviest round, the slug is essentially a large, bulky bullet with a breakaway plastic sleeve that it sheds once leaving the barrel. Slugs have the disadvantage of losing their airspeed extremely rapidly and being notoriously difficult to aim at ranges over 100m due to their bulky design. However, at any range, slugs inflict massive damage due to their sheer mass and speed. A typical 12 gauge shotgun round is a blunt one-ounce hunk of metal that is roughly described as a .750 calibre round weighing 432 grains (approx. 28 grams). For comparison, a standard deer rifle round, the .308 calibre (7.62 × 39mm), is only 150 grains (9.72g).

    • Shotshells and Buckshot

      For hunting small animals or fowl, the preferred ammunition for a shotgun is shotshells or buckshot. These are two different names for essentially the same thing, the only difference being size, with buckshot larger than shotshells. This ammunition is actually a hefty powder charge in a hard plastic cylinder behind anywhere from nine to a hundred metal spheres, depending on the shot number. Birdshot is typically considered anything that can be simply weighed into a shell rather than requiring hand-stacking, from #12 size (.05 inch, 1.27mm pellets) to #2 (.15 inches, 3.81mm) and BBs (.18 inches, 4.57mm). Buckshot comes in several sizes, from #4 (each pellet .24 inches, 6.1 mm in diameter), down to #000 (triple-aught buck), which has .36 inch (9.14mm) pellets.

  • Bolt

    The bolt is the device that causes the bullet in rifles and SMGs to slide forward into the chamber. When the round is discharged, semi-automatic weapons automatically push the bolt backwards. This ejects the now empty spent brass cartridge and feeds in a new round. Recoiling bolts help to absorb some of the recoil or shock of firing, as well as greatly improving consistent shooting posture and speed of fire.

  • Hammer

    The portion of a firearm at the back that can be cocked. When it is released, the hammer strikes the firing-pin, which strikes the rear of the cartridge, causing the powder to ignite and propel the bullet out of the rifle.

  • Firing Pin

    A small pin which, once the trigger is pulled, strikes the blasting cap at the back of the cartridge and ignites the powder within.

  • Chamber

    The portion of the firearm in which the cartridge is held, immediately before being discharged. In revolvers, the cylinder itself contains a number of tiny chambers, each holding one bullet within.

  • Slide

    In automatic pistols, the uppermost portion of the weapon. When loading and unloading the pistol, one must pull firmly back on the slide to either advance the first round into the chamber or eject a cartridge from the chamber, when loading and unloading. Each time the weapon is fired, the slide kicks backwards and performs both of these actions automatically.

  • Magazine

    A magazine9 is a device that both stores a number of rounds and allows them to be fed directly into the weapon's chamber, enabling shots to be fired in quick succession. There are two kinds of magazines, detachable and fixed, and they come in different styles, including box, rotary (including cylinder) and drum.

    • Box

      The most popular type of magazine, A standard detachable box magazine holds a number of rounds stacked on top of one another, and is inserted into the weapon where spring tension from the base of the magazine presses the rounds against the base of the chamber. As the chamber slides open, the rounds are automatically fed into the chamber itself each time the empty chamber is presented.

    • Cylinder

      The most popular style of rotary magazine used with revolvers, either fixed or detachable. The metal cylinder fits between the hammer and the barrel, with usually between four and twelve small holes in it. Each hole contains a round. When the cylinder is locked in place and the hammer drawn back, a hole in the cylinder aligns itself with both the barrel of the weapon and the hammer. Once fired, the cylinder revolves and automatically aligns the next chamber, and round, with the hammer.

    • Drum

      Usually used exclusively by some light machine guns, rounds are stored in a large drum-shaped cylinder. Drums normally contain more rounds than either a box or cylinder. The most famous drum submachine gun is the Thompson, which is often seen in gangster films set in the 1930s.

  • Belt

    An alternative to a magazine, usually used with machine guns. Belts hold cartridges and allow them to be quickly fed into the gun and fired in quick succession. Originally belts were made out of cloth just like a belt, more recently belts have been built of metal links which prove more reliable over frequent use.

  • Clip

    A clip clips rounds of ammunition together, ready to be inserted into a magazine or gun, speeding up the loading process. 'Clip' is often used incorrectly to refer to magazines, but technically, though similar, it serves a different purpose.

  • Rifling

    This describes the way the interior of a barrel is grooved. Putting rifling inside of a barrel in a corkscrew manner causes the bullets to rotate in their flight path, giving them a greater degree of accuracy. The rifling number indicates the number of grooves, while the ratio is the number of full rotations made in a given length. A 1:11 ratio, for example, means that the rifling makes one full rotation in eleven inches (0.279m). When bullets pass through the barrel they are usually grooved according to the rifling pattern inside the barrel, depending on type of bullet. Rifling patterns on bullets can be used to determine which type and make of weapon fired a bullet.

  • Cocking

    The act of drawing back the hammer of a weapon in preparation of firing the weapon. This can also mean loading a round into the chamber, as with several weapons the act of cocking them loads as well. In terms of SMGs, machine guns, and assault rifles, cocking the weapon is known as 'charging' it, which means locking the bolt in place in preparation of firing.

  • Minute of Angle (MOA)

    This is a specific statement regarding the accuracy of a weapon. Without getting into the math, a value of 1 MOA is equivalent to 1.047 inches (26.6mm) at 100 yards (91.4m). Therefore, given ideal shooting conditions and discounting human error, a weapon with an MOA of 1 will put every round within a 1.047-inch circle at a distance of 100 yards. This becomes a 2.094 inch circle at 200 yards, 3.1 inches at 300, etc.

  • Muzzle Brake

    A muzzle brake is designed to control both the light flash of a discharged round and the direction of the gases exiting the barrel. Instead of belting the gases forward directly out of the weapon, it vents them to the sides and slightly rearward, compensating for both the climb of the rifle and the recoil, or force of the fired round, itself.

One of the finest collection of small arms in the world can be found at the Royal Armouries, Leeds.

1Also known as the arquebus.2Traditionally heavy weapons found on ships were known as 'guns' when their land-based equivalents were known as 'cannon'.3The cylinder in some pistol designs can also be a detachable magazine.4A bore is the inside of the gun's barrel.5This is short for Sturmgewehr 44, storm rifle, 1944 model.6The subject of a poem by Hilaire Belloc after the First Matabele War when 50 soldiers armed with 4 Maxims reportedly defeated 5,000 Ndebele warriors. This read Whatever happens, we have got / the Maxim gun, and they have not.7Early examples were labelled Quick Firing or QF guns.8In some 'rimfire' weapons the blasting cap or 'primer' is in a rim around the back of the cartridge case, although these are not as common.9Originally a magazine was a dedicated room where ammunition was stored.

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