Gun Encyclopedia

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Ammunition - Handgun

Ammunition -Rifle

Anti-materiel Rifle

An anti-materiel rifle is generally a large-caliber rifle used in peacetime for destroying equipment and unexploded ordnance, and during wartime for attacking unarmored or lightly armored vehicles, fuel dumps, parked airplanes, etc. Though most similar in form to sniper rifles there is not as much focus on accuracy and more concern for effectively damaging a target. The roots of the field go back to World War I and the first anti-tank rifle.

Assault Rifle

An assault rifle is a type of automatic weapon. It is generally defined as a selective-fire rifle or carbine (depending on the particular firearm's size), using intermediate-powered ammunition. It can be considered a compromise between the battle rifle, firing full-power rifle ammunition, and the less powerful submachine gun, which uses pistol ammunition. Assault rifles are standard small arms in most modern armies. The name is a literal translation of the German term Sturmgewehr, first applied to the Sturmgewehr 44 developed during WW2, and gradually became a popular term for this type of firearm. The term has since been retro-actively applied to earlier weapons with similar traits.

Automatic

An automatic firearm is a firearm that will continue to load and fire ammunition as long as the trigger (or other activating device) is pressed or until it runs out of ammunition. The M2 machine gun, the M60 machine gun and the M134 Minigun are examples of full-automatic weapons, as are the autocannon mounted on many military aircraft and used in other applications such as anti-aircraft defense.Although automatic firearms (by definition) are capable of full-automatic fire, most also have a selective fire capability, meaning that they can be used as a semi-automatic firearm generally by manipulating a selector switch (as with the M16), or by pressing the trigger further to the rear, as with the Steyr AUG assault rifle. So-called "automatic" pistols, however, are actually semi-automatic in operation, firing a single shot for each trigger press, automatically ejecting the spent cartridge and loading a fresh one into the chamber. Though they are correctly referred to as "automatic pistols", the nature of their action is, in fact, semi-automatic and that distinction is necessary for description in the popular press. Full-automatic weapons tend to be restricted to military and police personnel in most developed countries. In the United States, they have been off the public market since the Gun Owners Protection Act of 1986.

Ballistics

Ballistics (gr. ba'llein, "throw") is the science that deals with the motion, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and hurling projectiles so as to achieve a desired performance. A ballistic body is a body which is free to move, behave, and be modified in appearance, contour, or texture by ambient conditions, substances, or forces, as by the pressure of gases in a gun, by rifling in a barrel, by gravity, by temperature, or by air particles. Firearm ballistics information is used in forensic science. Separately from ballistics information, firearm and tool mark examinations involve analyzing firearm, ammunition, and tool mark evidence in order to establish whether a certain firearm or tool was used in the commission of a crime. Ballistics is sometimes subdivided into: Internal ballistics, the study of the processes originally accelerating the projectile, for example the passage of a bullet through the barrel of a rifle; Transition ballistics, the study of the projectile's behavior when it leaves the barrel and the pressure behind the projectile is equalized. External ballistics, the study of the passage of the projectile through space or the air; and Terminal ballistics, the study of the interaction of a projectile with its target, whether that be flesh (for a hunting bullet), steel (for an anti-tank round), or even furnace slag (for an industrial slag disruptor).

Bipod

A bipod is a support device that is similar to a tripod or monopod, but with two legs. It provides significant stability along two axes of motion (side-to-side, and up-and-down.) On firearms, bipods are commonly used on sniper rifles to reduce motion and permit more accurate shooting. They are also seen on other long-barreled weapons, especially light machine guns or squad automatic weapons. Machine guns are capable of firing long continuous bursts of fire, but at the cost of increased recoil (which decreases accuracy), and increased weight (machine guns are heavier in order to absorb the stresses of prolonged fully-automatic fire.) The bipod permits the operator to rest the weapon on the ground, a low wall, or other object, reducing operator fatigue and permitting increased accuracy.

Blank

A blank is a type of cartridge for a gun that contains gunpowder but no bullet or shot. Blanks are commonly used for safety reasons in military training maneuvers, and in starter's pistols to signal the beginning of races. However, it should be noted that given the explosiveness of a blank cartridge they are by no means safe. While blanks do not contain bullets, they often contain a paper or plastic plug that seals the powder in the case, called a wad (a term derived from shotgun shells). This wad can cause bruising at medium ranges and severe penetrating wounds at close range.

Blowback Action

Blowback is one particular system in which an automatic or semi-automatic firearm may operate. In the blowback system there is no positive lock between the bolt and the barrel. The mass of the bolt and force of its recoil spring act to keep the breech closed. The expanding gases from the fired round overcome this inertia and "blow back" the breech. The breech must be kept closed until the round has left the barrel and gas pressures have subsided. The weight of the bolt is the major factor in determining this, and to remain practical this system is only really useful for weapons using relatively low pressure rounds. Blowback operation is typically found only on semi-automatic small-caliber pistols and automatic submachine guns.

Bolt Action

A bolt-action firearm is typically a rifle that is manually operated (i.e. by hand), specifically that the opening and closing of the breech is controlled manually by a bolt. The term "action" references the means by which a firearm operates. Typically, the bolt consists of a tube of metal inside of which the firing mechanism is housed, and which has at the front or rear of the tube several metal knobs, or "lugs", which serve to lock the bolt in place. The operation can be done via a rotating bolt, a lever, or a number of systems. For example, one setup is a straight-pull design that use a rotating bolt, such as the German Blaser R93 rifle. Straight pull designs have seen a great deal of use, though manual turn-bolt designs are what most commonly thought of in reference to a bolt-action design due to the type ubiquity. As a result the bolt-action term is often reserved for more modern types of rotating bolt-designs when talking about a specific weapon's type of action, however both straight pull and rotating bolt rifles are types of bolt-action rifles. Most bolt-action firearms are fed by an internal magazine loaded by hand, by en bloc, or stripper clips, though a number of designs have had a detachable magazine or independent magazine, or even no magazine at all, thus requiring that each round be independently loaded. Typically, the capacity has been limited to several rounds, as it can permit the magazine to be flush with the bottom of the rifle, reduce the weight, or prevent mud and dirt from entering. A number of older bolt actions had a tube magazine, such as along the length of the barrel.

Bullet

A bullet is a projectile shot by a gun, usually made of a metal alloy. In contrast to a shell, a bullet does not contain explosives. The term bullet refers specifically to the metal slug that is propelled from a firearm. Although the term is occasionally used to refer to the combination of bullet, case, gunpowder, and primer, such an item is properly called a cartridge. A cartridge without a bullet is called a blank.

Caliber

In firearms, the caliber is the diameter of the inside of the barrel. In a rifled barrel the distance is measured between the lands. The measurement is in inches and the caliber (abbreviated to cal) is quoted as a fraction (hundredths or thousandths) of an inch, so a 0.22 inch smallbore rifle is .22 cal. Outside Great Britain and the U.S., the caliber of a weapon is commonly expressed in millimeters (mm). The caliber of a weapon is often informally used to describe certain common weapons. A .45 cal pistol is called a '45', a 9 mm semi-automatic pistol is called a '9 mil', a .380 caliber is called a '380', etc. This gives rise to the impression that "cal" is a unit of measurement, equal to 1/100 or 1/1000 of an inch, whereas it is rather a figure of speech. For historical reasons, the name of a cartridge is not always the actual caliber. As one example, the common .38 Special revolver actually fires a bullet 0.357 inches in diameter.

Carbine

A carbine is a firearm similar to, but generally shorter and less powerful than a rifle or musket of a given period. There have been many carbines developed from rifles, being essentially shorter rifles firing the same ammunition, although usually at a lower velocity. However, there are other cases where the carbine and rifle adopted by a particular nation were unrelated, using completely different ammunition. The shorter length and lighter weight of carbines makes them easier to handle in close-quarter combat situations (such as urban or jungle warfare), or when deploying from vehicles. The downside of carbines, when compared with their longer counterparts, is generally poorer long-range accuracy and shorter effective range.

Casing

A casing, also called case or the brass, is the part of a cartridge that contains the gunpowder charge, the primer, and the bullet. After a shot is fired, the casing is empty as its gunpowder charge has burned, as the primer has been used and as the bullet has been propelled. The empty case is often ejected automatically.After a crime committed with a firearm the police attempt to collect cases and bullets used in weapons associated with the crime.

Chamber

In firearms, the chamber is the part of the barrel in which the cartridge is inserted prior to being fired. Rifles and pistols have a single chamber in their barrel, while revolvers have multiple chambers in their cylinder and no chamber in their barrel. The act of chambering a round means the insertion of a ound into the chamber, either manually or through the action of the weapon.

Closed Bolt

A semi or fully-automatic firearm which is said to fire from a closed bolt is one where, when ready to fire, a round is in the chamber and the bolt and working parts are forward. When the trigger is pulled the firing-pin or striker fires the round, the action is cycled by the energy of the shot sending the bolt to the rear which ejects the empty cartridge case, the bolt then goes forward feeding a fresh round from the magazine into the chamber, ready for the next shot.

Firearm

A firearm is a kinetic energy mechanical device that fires either single or multiple projectiles propelled at high velocity by the gases produced by action of the rapid confined burning of a propellant. This process of rapid burning is technically known as deflagration. In older firearms, this propellant was typically black powder, but modern firearms use smokeless powder or other propellants. The term gun is often used as a synonym for firearm, but in specialist use has a restricted sense—referring only to an artillery piece with a relatively high muzzle velocity and a relatively flat trajectory, such as a field gun, a tank gun or an anti-tank gun, or a naval gun. Guns are distinct from howitzers and mortars, which have lower muzzle velocities and higher trajectories. Hand-held firearms, like rifles, carbines, pistols and other small firearms are never called "guns" in the restricted sense.

Flintlock

Flintlock is the general term for any firearm based on the flintlock mechanism. The type is now obsolete. Introduced about 1630, it rapidly replaced earlier types, such as the matchlock and wheellock, and continued in common use for over two centuries, replaced by cap and cartridge-based systems. The last major use of flintlocks in the Americas occurred in the first years of the American Civil War; however, a few guns of this type are still manufactured for black powder enthusiasts.

Gas Actuated Action

The gas-operated system for implementing automatic reloading of a firearm is one of five such systems, the others being recoil-operated, Gatling, chain, and blowback. In a gas-operated system some of the expanding gases from the round being fired are routed from a port just behind the muzzle (where the pressure is lower) in front of a piston, typically lying over the barrel. The piston is forced backwards by the gas, and is connected to the breech of the gun, which is unlocked by the backwards motion induced by the piston when the round leaves the barrel. This system is useful for machine guns and assault rifles, and permits use of a long barrel and makes efficient use of the propellant. Usually, the speed at which the weapon fires is determined by a regulator, which controls the gas flow to the piston. The greater the gas flow, the faster the weapon will fire. This also means the faster the shot is fired, the more warping and jamming caused by overheating. Weapons using this type of automatic reloading include the HK G36, AK-47 and derivatives. The M-16 uses direct impingement, which is a version of gas operation without a piston.

Gas Delayed Blowback Action

Gas-delayed blowback (also called gas-retarded blowback) is a firearm operating principle (not to be confused with gas-operated). The bolt is never really locked, and so is pushed rearward by the expanding propellant gases as in other blowback-based designs. However, propellant gases are vented from the barrel into a cylinder with a piston that delays the opening of the bolt. Gas-delayed blowback is one of the rarer operating principles. It is used by the HK P7 and Steyr GB pistols.

Gunpowder

Gunpowder is a substance which burns very rapidly and is used as a propellant in firearms, specifically either black powder or smokeless powder. As it burns, a subsonic deflagration wave is produced rather than the supersonic detonation wave which high explosives would produce. This reduces peak pressures in a gun.

Headspace

In firearms terms, headspace refers to the distance between the bolt face and chamber necessary for reliable functioning of the weapon, or as a verb, the mechanism by which the correct positioning is achieved. The headspace is measured from the part of the chamber that stops forward motion of the cartridge to the face of the bolt. For example, 5.56 NATO ammunition headspaces off the shoulder of the cartridge. .303 British headspaces off the rim of the cartridge. Headspace is measured with a set of headspace gages. Each caliber typically has a minimum and maximum gauge. The bolt must lock on the minimum gauge, and must not lock on the maximum. Headspace is important for the proper functioning of the firearm. If the headspace is too short, ammunition that is in specification may not chamber correctly. If headspace is too large, the cartridge case may rupture, damaging the weapon or injuring the shooter.

Hydrostatic Shock

Hydrostatic shock is the effect commonly believed to be caused by a high velocity object entering a body, such as a bullet fired from a weapon. The shock is described in the following way—the object will cause ordinary damage by the actual penetration, but also pass a shock wave in the surrounding tissue due to the energy of the slowing object being passed into the largely liquid material of the body (65%+). The shock wave, or sometimes competing shockwaves from multiple impacts, are believed to cause greater damage than the object itself, sometimes enough to rupture internal organs and fracture bone. Especially large objects are believed to cause hydrostatic shock by the closure of the cavity created by the object's passage. There is a body of opinion, however, that believes hydrostatic shock is errant nonsense. The argument is based around how energy is transferred and the effects of such a transfer. Issues raised include kinetic energy vs. momentum, the rate of energy transfer, thermodynamics (kinetic energy would be transformed into heat), the speed of sound in tissue, hydrodynamic effects, 'wound tracks', and the nature of a body.

Kinetic Energy

Kinetic energy is energy that a body has as a result of its speed. It is formally defined as work needed to accelerate a body from rest to a velocity v. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work would also be required to return the body to a state of rest from that velocity.

Lever Action

A lever-action is a type of firearm which uses a lever located around the trigger guard area (often including the trigger guard itself) to load fresh cartridges into the chamber of the barrel when the lever is "cranked". The most famous of such lever-action firearms are the Martini-Henry and the Winchester rifle, but many manufacturers produce lever-action rifles. Both Marlin and Winchester have a model 1894 lever action rifle, as both manufacturers released them in that year. The Marlin has a single stage lever action, and the Winchester has a double stage. This is hard to describe, but is easy to notice when the two are compared.A very significant lever-action design was the Spencer repeating rifle. The design was completed by Christopher Spencer in 1860 and was a magazine-fed lever-operated breechloader rifle. The firing system had to be independently primed, a lever had to be cocked, and it used copper rimfire cartridges. It was fed from a removalable seven round tube magazine, enabling the rounds to be fired one after another, and which, when emptied could be exchanged for another. It was adopted by the United States and used during the American Civil War, with over 20,000 made. This marked the first adoption of a removable magazine-fed infantry rifle by any country. Lever-action rifles were popular, but less so among the military because they were harder to fire from the prone position than straight pull or bolt-action rifles. From other positions they were faster than either to reload, but they they were gradually phased out in the early 1900s.They have remained popular for civilian rifles up to the present, and there are also many lever-action shotguns.

Light Machine Gun

A light machine gun (LMG) is a categorization type, or class of machine guns that are generally lighter than other of machine guns of its period, and usually designed to be carried by an individual soldier, but sometimes with an assistant. In practice, they are either automatic rifles (machine rifles) or medium machine guns with a bipod, a stock, and sometimes a pistol grip. Modern light machine guns are often lighter caliber, in addition to being lighter weight. Usually an LMG, or LMG version of a firearm is intended to act as a support weapon in that it can generate a greater volume of continuous fire than the usual firearms carried by infantry soldiers, but at the cost of greater weight and higher ammunition consumption. While it is usually possible to fire an LMG "from the hip" or on the move, they are much more accurate when fired from a prone position, especially when using a bipod. They are often designed to be used with magazines, not belts, but some, such as the M249, use both. Light machine guns are often used as squad automatic weapons.

Machine Gun

Unlike semi-automatic firearms, which require one trigger pull per bullet fired, a machine gun is designed to fire bullets as long as the trigger is held down and ammunition is fed into the weapon. Although the term "machine gun" is often used to describe all fully-automatic weapons, in military usage the term is restricted to weapons designed to provide suppressive fire in continuous or frequent bursts of automatic fire for as long as ammunition lasts (however, a fully automatic firearm with a projectile caliber of equal to or greater than 20 mm (0.8 inch) is called an automatic cannon). Some machine guns have in practice maintained suppressive fire almost continuously for hours; other automatic weapons will eventually overheat, usually in less than a minute. Because they become very hot in operation, practically all machine guns fire from an open bolt, to permit air cooling from the breech between bursts. They also have either a barrel cooling system or removable barrels (so that a hot barrel can be swapped for a cool one.) Although subdivided into "light", "medium", "heavy" or "general purpose", even the lightest machine guns tend to be substantially larger and heavier than other automatic weapons. Squad automatic weapons (SAWs) are a variation of light machine guns and only require one operator (sometimes with an assistant to carry ammunition). Medium and heavy machine guns are either mounted on a tripod or on a vehicle; when carried on foot, the machine gun and associated equipment (tripod, ammunition, spare barrels) require additional crew members. The majority of machine guns are belt-fed, although some light machine guns are fed from drum or box magazines, and some vehicle-mounted machine guns are hopper-fed.

Magazine

A magazine is an ammunition storage device within or attached to a firearm. The magazine may be integral to the firearm (fixed) or removable (detachable). The cartridges in the magazine are loaded into the firearm either automatically or manually depending on the type of gun, but almost always by a spring. Some magazines can in turn be loaded by a clip; contrary to the common misconception, 'clip' and 'magazine' are not synonymous. An example of this misuse is the use of 'banana clips' to refer to curved box magazines, although this particular phrase is not as common as the more proper 'banana magazine'. The most common type of magazine is the detachable "box" type. However, other types are available, such as the "drum" magazine sometimes used with the Thompson submachine gun, the "pan" magazine of the Russian DP-28 machine gun, and the fixed "tube" magazine found on many lever-action rifles and pump-action shotguns. Magazines for a particular firearm may come in different shapes and sizes. Certain magazines are unmistakable in their appearance, such as those of the AK-type assault rifles, while with others it can be more difficult to tell what gun they belong to, such as when comparing the Ruger Mini-14's magazines with AR-15/M16 magazines.

Matchlock

Matchlocks were the first and simplest small arms firing mechanisms developed. Using the matchlock mechanism, the powder in the gun barrel was ignited by a piece of burning cord called a "match". The match was wedged into one end of an S-shaped piece of steel. As the trigger (often actually a lever) was pulled, the match was brought into the open end of a "touch hole" at the base of the gun barrel, which contained a very small quantity of gunpowder, igniting the main charge of gunpowder in the gun barrel. The match usually had to be relit after each firing.

Medium Machine Gun

A Medium Machine Gun or MMG in modern terms, usually refers to a belt fed, full power rifle caliber (such as 7.62 mm rifle caliber) automatic weapon with some provision for more extended firing than lighter automatic firearms, often using an extra-heavy barrel, fins, barrel-changing, or even a water cooling jacket; but they are light enough to be used by infantry with a bipod. (typically they weigh between 15 and 40 pounds). The descriptor is a grey area, especially historically, and occupies a uncertain realm between machine guns called light and heavy. Two features which have remain somewhat constant however, are some added ability for greater fire over automatic rifles, and the ability to be used in both light infantry support roles on a bipod, but also on mounts and tripods. While heavies are rarely, if ever used on bipods, and lighter machine guns are rarely if ever mounted, mediums have historically been used in both. Heavy machine guns are either crew-served or mounted, while mediums are usually operated by 1-2 soldiers. Light machine guns and automatic rifles are often a individual weapon with a fixed, naked barrel. On the other hand medium machine guns have usually had more endurance of some sort, such as the aforementioned heavier barrel, barrel change, fins, etc.

Minigun

The term Minigun actually orginates in the 1960s when a larger caliber weapon was scaled down to a 7.62 mm rifle caliber and the resulting weapon was dubbed the minigun by the manufacturer, General Electric. It started to be used by the U.S. military starting then, especially as helicopter door-gun, but was also adopted for many other roles and in other Services. It has been used in most major U.S. military operations since then, as well as being adopted by other countries. The GE Minigun is in use in all major branches of the US military, under a number of designations. The basic fixed armament version was given the designation M134 by the US Army, while the exact same weapon was designated GAU-2B/A by the US Airforce. A variant was further developed by the US Airforce specifically for flexible installations, at the time primarily for the UH-1N helicopter, as the GAU-17/A. The primary end users of the GAU-17/A have been the US Navy and the US Marine Corp, who mount them on as defensive armament on a number of helictopers. Also, the weapon has been fitted as armament on a variety of surface ships. In two pictures released by the USN, these weapons were described as GAUSE-17/As, but there is no official mention of this designation outside of these pictures, and it is generally believed to be a misnomer or similar error.

A Minigun is also a general term for a multibarreled machine gun with a high rate of fire (several thousand rounds per minute), employing Gatling-style rotating barrels. More technically it is a externally powered gatling gun of a smaller caliber, though it is sometimes used more generally to refer to ones of similar rates of fire and configuration regardless of power source. In popular culture, its any sort of machine-gun like rapidly firing gatling multi-barrel gun, and often found in movies and video/computer games (e.g Predator (1987)). For example, the GShG 7.62 was a Soviet gas-operated rotary machinegun of caliber 7.62x54 mm with four barrels. There were also other gatling type's in larger caliber as well. While very similar in many ways and somtimes mistaken for a minigun, because it was gas-operated rather than externally powered it has some different traits.

Muzzle brake

A muzzle brake or compensator is a device that is affixed to the muzzle of a firearm, and which redirects propellant gases to either counter the recoil of the gun, or to prevent the muzzle from climbing during rapid fire. They are very useful for combat and timed competition shooting, and are commonly found on rifles firing very large cartridges (often big-game rifles), as well as some artillery and tank guns. They are also commonly used on pistols for practical pistol competitions, and are usually called compensators in this context.

Muzzle brakes are simple in concept. One of the simplest designs can be found on U.S. 90 mm tank guns, which consisted of a small length of tubing mounted at right angles to the end of the barrel. As the shell left the barrel the gases would rush around it, hitting the inside "front" of this tube, pushing it, and thus the gun as a whole, forward. Brakes more typically consist of a small length of tubing "fit over" the end of the barrel, pointing in the same direction. Slits or holes are cut into the tube, angled toward the rear of the gun. When a round is fired there is a brief period in which the bullet is at the end of the brake, but not yet exited. During this time the gases pushing the round escape through the holes to the rear, countering the recoil.

There are advantages and disadvantages to muzzle brakes on firearms. Despite manufacturers claims of recoil reduction of 50% and more, that is really physically impossible. What is really happening is that because the muzzle break tends to reduce lateral movement as well as recoil to the shooter it may well feel like half the recoil has been mitigated. The other two primary advantages to the muzzle brake are that because they minimize lateral movement of the barrel the gun does not move far off target facilitating quick reacquisition of the target for additional shots. This is a big advantage on fully automatic weapons. The other thing that well designed muzzle brake does is increase accuracy. The gasses rushing by the round just as it leaves the barrel can cause it to be deflected; by diverting the gasses at exactly this point this deflection can be reduced. Certain types of muzzle brakes slightly stabilize the bullet at this juncture and noticeably decrease shot to shot deviation.

The disadvantage to a muzzle brake is that it is directing propellant gasses at a 90-degree angle to the line of fire, the consequence of this is that it is effectively directing the weapons report sideways as well. Weapons with muzzle brakes sound significantly louder, particularly to anybody on either side of the weapon. Another disadvantage of the muzzle brake is that because they are diverting super hot propellant gasses at right angles to the bore of the weapon, the muzzle flash is significantly larger. Although this is not readily apparent in daylight, at night it is brilliantly apparent, which is a particular issue to the military. Some muzzle brakes are better than others in regard to muzzle flash but nobody has yet designed a muzzle brake that can minimize muzzle flash to the level of that achieved with modern military flash hiders of the Vortex design. Muzzle brakes on both small arms and artillery pieces can also cause escaping gases to throw up dust clouds, obscuring visibility and making the firer easier to spot by the enemy. Troops often wet the ground in front of antitank guns in defensive emplacements, to prevent this.

Muzzleloader

Muzzle-loading muskets (smooth-bored long guns) were among the first small arms developed. The firearm was loaded through the muzzle with gunpowder, optionally some wadding and then a bullet (usually a solid lead ball, but musketeers could shoot stones when they ran out of bullets). Greatly improved muzzleloaders are manufactured today and have many enthusiasts, many of whom hunt large and small game with their guns. Muzzleloaders have to be manually reloaded after each shot; a skilled archer could fire multiple arrows faster than most early muskets could be reloaded and fired, although by the mid-18th century, when muzzleloaders became the standard small armament of the military, a well-drilled soldier could fire six rounds in a minute using prepared cartridges in his musket. Before then, effectiveness of muzzleloaders was hindered by both the low reloading speed and, before the firing mechanism was perfected, the very high risk posed by the weapon to the person attempting to fire it. One interesting solution to the reloading problem was the "Roman Candle Gun". This was a muzzleloader in which multiple charges and balls were loaded one on top of the other, with a small hole in each ball to allow the subsequent charge to be ignited after the one ahead of it was ignited. It was neither a very reliable nor popular firearm, but it enable a form of "automatic" fire long before the advent of the machine gun.

Open Bolt

A semi or fully-automatic firearm which is said to fire from an open bolt is one where, when ready to fire, the bolt and working parts are held to the rear. When the trigger is pulled the bolt goes forward, feeding a round from the magazine into the chamber and firing it. Like any other self-loading design, the action is cycled by the energy of the shot; this sends the bolt back to the rear, ejecting the empty cartridge case are preparing for the next shot.

Physics

For the viewpoint of physics (dynamics, to be exact), a firearm, as are most weapons, is a system for delivering maximum destructive energy to the target with minimum delivery of energy and momentum back to the shooter. It should be noted that the impact to the target can be no greater than the impact of the recoil, due to the law of conservation of momentum. However, the smaller size of the bullet, compared to the gun-and-shooter system, allows significantly higher energy to be imparted to the bullet than to the shooter, giving guns their lethal effect. Consider a system where the shooter-and-gun have mass M and the bullet has mass m, and the two systems move away from one another with new velocities V and v. Then, by the law of conservation of momentum, MV = mv, and thus V = mv/M and the kinetic energies imparted to the two systems are respectively 1/2 MV² and 1/2 mv². The energy imparted to the shooter can then be written as

Thus the ratio of the energies is the same as the ratio of the masses of the bullet and the shooter. However, almost all of the energy will be dissipated in the target. When the bullet strikes, its high velocity and small area means that it will exert large stresses in any object it hits. This usually results in its penetrating any soft object, such as flesh. The energy is then dissipated in the wound tract formed by the passage of the bullet. See terminal ballistics for a fuller discussion of these effects. The reversal of this mathematics is the reason why bulletproof vests work: the vest's material, usually Kevlar, works by presenting a series of material layers which catch the bullet and spread its momentum, hopefully bringing the round to a stop before it can penetrate into the body. People who wear this kind of vest also have to remember that while it can prevent a bullet from penetrating, they can still be affected by the kinetic energy of the bullet which can produce serious internal injuries. Hollywood depictions of firearm victims being thrown through plate-glass windows are inaccurate, as were this to be the case, the shooter would also be thrown backwards with equal force. Gunshot victims frequently fall or collapse when shot; however this is usually due to physical damage or psychological effects perhaps combined with being off-balance, not the momentum of the bullet pushing them over. (Note that the above paragraph does not apply if the victim is hit by heavier projectiles such as 20 mm cannon shell, where the momentum effects can be enormous; this is why very few such weapons can be fired without a weapons mount.)

Pistol

Nowadays there are three main varieties of pistol: "automatic" self-loading pistols and revolvers being by far the two most common types, followed distantly by single-shot hunting or target pistols. In a pistol the "chamber," in which the cartridge is held for firing is the rearmost portion of the barrel. Thus the term "pistol" technically excludes revolvers, although this distinction is often ignored in colloquial usage, where revolvers are commonly referred to as "pistols."

Primer

The percussion cap or primer was the crucial invention needed to make fire-arms that could fire in any weather. Before this development, firearms used igniters with flints or matches to set fire to a pan of gunpowder. A primer is a small, disposable copper or brass cup, 4 to 6mm in diameter (standard sizes are 0.175 inches and 0.210 inches for handgun and rifle cartridges). In the cup is a precise amount of stable, but shock-sensitive explosive mixture, with ingredients such as lead azide or potassium perchlorate. A striker hits the outside of the cup, which bends, and the explosive is crushed on an anvil. The shock-sensitive chemical compound explodes, igniting a secondary charge of gunpowder or other explosive. Caps were originally manually placed on nipples on the outside of single-shot muzzle-loading weapons. Pulling the trigger released a hammer to crush the cap against the nipple. Eventually, caps were incorporated into the rear of metallic cartridges. A small stamped anvil was added to the design, placed inside the cup to make the modern replaceable primer. Corrosive primers use stable, long-lived explosives that generate corrosive residues in a gun, usually metallic oxides which, when exposed to moisture, form hydroxides. They are popular with the many militaries because they work reliably under severe conditions. Noncorrosive primers are somewhat less reliable when stored for many years, but far easier on guns. Most civilian ammunition uses noncorrosive primers. New on the market in the late 1990s are lead free primers, which address the concerns over the lead and other heavy metal compounds found in other primers. The heavy metals, while small in quantity, is released in the form of a very fine soot, and many indoor firing ranges are moving to ban primers containing them for the potential health risk they pose. Lead free primers were originally less sensitive (and thus less reliable) and had a much greater moisture sensitivity and correspondingly shorter shelf life than normal noncorrosive primers. Since their introduction, lead free primers have improved to the point that they are nearly equal in performance to lead based primers, and will likely become the norm in the near future.

Pump Action

A pump-action rifle or shotgun is one in which the fore-end of the stock can be pumped back and forth in order to eject and chamber a round of ammunition. It is a little faster than a bolt-action or lever-action, as it does not require the trigger hand to be removed from the trigger whilst reloading.

Recoil

The recoil when firing a gun is the backward momentum of a gun, which is equal to the forward momentum of the bullet or shell, due to conservation of momentum. It has to be absorbed by for example the wrist, the shoulder or the carriage. For handguns it has to be limited to avoid breaking one's wrist, see also cartridge. It should be noted that the impact to the target can be no greater than the impact of the recoil, due to the law of conservation of momentum. However, the smaller size of the bullet, compared to the gun-and-shooter system, allows significantly higher energy to be imparted to the bullet than to the shooter. This is what gives guns their lethal effect. See physics for a more detailed discussion. Hollywood depictions of firearm victims being thrown through plate-glass windows are inaccurate, as were this to be the case, the shooter would also be thrown backwards with equal force. However, gunshot victims frequently do collapse when shot, but this is usually due to the effect of the energy of the bullet on their body systems, not the momentum of the bullet pushing them over. Of course this does not apply if the victim is hit by heavy weapons fire such as aircraft cannon, where the momentum effects can be enormous. This is why these weapons need to be mounted on a weapons platform. A recoil system absorbs momentum, for example by the barrel moving backwards. Cannons and such weapons without a recoil system roll several meters backwards when fired. In a soft-recoil system, a gun's barrel is moved forward prior to shooting. As the barrel is forced backwards by the recoil force, the energy is reduced by friction, resulting in less of an overall "kick". One of the early guns to use this was the French 65mm mle.1906; however, this method did not receive much attention until the 1970s. Recoilless rifles exhaust gas to the rear, balancing the recoil. They are used as light anti-tank weapons.

Recoil Actuated Action

Recoil operation is one of the firearm actions used in automatic firearms. It uses the recoil of the barrel to cycle the action. There is a difference between "blowback" and "breechblock" actions. Recoil operated guns designed for low pressure, low "power" ammunition have "blowback" actions, and recoil operated guns designed for high pressure, high "power" ammunition have "breechblock" actions. The pressure generated by the propellant is so high that it would burst the cartridge case if it was not supported. Normally the sides of the cartridge case are supported by the chamber walls and the head of the cartridge case is supported by the breech. To prevent a ruptured cartridge case, the cartridge case should not be extracted until the pressure acting on the walls of the cartridge case is at a safe level; this means that the bullet has traveled far enough down the barrel so that the pressure has dropped, or the bullet has left the muzzle and the gas has vented out the muzzle. In lower pressure cartridges, such as .22 Long Rifle, .25 Auto, .32 Auto, or .380 Auto, it is feasible to design a practically useable "blowback" action, in which the barrel is fixed to the frame, and only the mass of the slide and the force of the recoil spring holds the gun closed long enough to support the case and delay extraction until a safe pressure has been achieved. Higher power cartridges, such as 9mm Luger, .40 S&W, or .45 Auto, generate much higher pressure; one could design a blowback action. But the slide would be so heavy as to make the gun difficult to control, or the recoil spring would be so stiff that it would be difficult to manually open the slide. So these guns have breechblock actions. This is how breechblock action works: 1. The recoil of the bullet going through and leaving the barrel, in the form of gas pressure, drives the breechblock and slide backward. 2. The barrel and the breechblock unlock. 3. Since the spring attaching to the barrel to the frame is firmer than the spring attaching to the slide to the frame, the barrel's cycling back into position is even faster than the slide's cycling, ramming the barrel clear of the breechblock. The extractor, which is a hook on one side of the breechblock, holds the case, pulls it out of the chamber, and the dedicated ejector spring in the breechblock, through the dedicated ejector pin, in the other side of the breechblock, holds the case against the walls of the chamber until the case can fully exit the chamber. The separation of the barrel and the slide opens a slot in the side of the slide that the barrel previously laid under and blocked. The slide flying back ratchets the action into a charged position, ready to strike the next primer. 4. The ejector spring and ejector pin throw an edge of the case forward, and the extractor holds its side of the case until the case spins so that the extractor cannot hold the case, so that the result is the flipping of the case outward. This ejects the spent cartridge's case through the slot in the slide and clears space for the next cartridge. 5. A spring in the magazine pushes all the cartridges up. One cartridge on the top of the pile ends up between the breechblock and the barrel, hooking the new case onto the extractor. 6. And the slide's spring rams the slide, breechblock against and the new cartridge into the barrel, putting the cartridge in the chamber, charging the ejector spring through the ejector pin, and locking the breechblock onto the barrel. The gun is just as it was before, minus one cartridge in the bottom of the magazine, plus heat, noise and the now closed gun recoiling back in the operator's hand(s). Some of the more common mechanical locks are: Tilt locked (Many Browning designs, Sturmgewehr 44) Falling-lock locked (Walther P38, Beretta 92FS) Rotating bolt (M1 Garand, M1 Carbine, M16, HK G36, AK-74, M1942 Johnson, M2 Mauser) Roller locking (MG-42) Toggle-locked Luger Browning Automatic Shotgun, Femaru STOP pistol. Radial Locking (Blaser 93) There is a further distinction between short-recoil and long recoil operation. (Short) recoil operation is common in pistols. The MG-42 machine gun and its descendant the MG-3 use recoil together with roller locking. The Maxim gun and the Barrett M82A1 heavy sniper rifle are also examples of recoil operation.

Revolver

Revolver-type weapons are part of the long development of making better multishot weapons. They were partly an attempt to improve on pepper-box type weapons, which used a revolving cylinder with one set of firing mechanisms, but had multiple barrels as well. Firing through a single barrel saved the expense and weight of having the multiple barrels of the Pepper-box. Revolvers have remained popular to the present day in many areas, although they have largely been supplanted by semi-automatic magazine-fed pistols such as the Colt 1911, especially in circumstances where reload time and higher cartridge capacity is important. 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 a double action revolver, the trigger pull can pull back the hammer as well as release it.

Most commonly, such guns have a five- or six-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 (even with the help of such devices as speedloaders). The alternatives are a replaceable cylinder, a speedloader 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.

Due to the simplicity of design, a revolver is easier to make and has higher reliability than other multi-shot firearms in extreme environments. For these reasons, such guns are the most commonly-owned weapons for personal self-defense and hunting, where their capability to fire powerful ammunition with great accuracy has maintained their popularity. 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 the cartridge firing. With a revolver this is not necessary as, as none of the energy for cycling the revolver comes from the firing of the cartridge, but is supplied by the user either cocking the hammer or, in a double action design, just pulling 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 .500 S&W is one of the most powerful, if not the most powerful revolver ever created.

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 that was compact enough to make a practical revolver.

The first generation of cartridge revolvers were converted caplock designs. In many of these (especially those that were converted after manufacture), the pin on which the cylinder revolved was removed, and the cylinder taken from the gun for loading. Later models used a loading gate at the rear of the cylinder that allowed one cartridge at a time accessed for loading, while a rod under the barrel could be pressed backwards to extract the fired case. Most revolvers using this method of loading are single action revolvers. Since the cylinder is firmly attached at front and rear of the frame, and since the frame is full thickness all the way around, most large caliber hunting revolvers tend to be single action. Oddly, the loading gate on the original Colt designs (copied by nearly all single action revolvers since) is on the right side, which slightly favors left handed users.

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.

The last and now 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 all 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 (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 rotating 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 provides a more secure bond between cylinder and frame, and allows the use of larger, more powerful cartridges.

Single 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, that of releasing the hammer. Because only a single action is performed and trigger pull lightened, firing a revolver in this way allows most shooters to achieve greater accuracy.

Double 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, and when the trigger is pulled, it 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) and then releases the hammer at the rear of its travel, firing the round in the chamber. Double action only revolvers lack the latch that enables the hammer to be locked to the rear, and thus can only be fired in the double action mode.

Automatic revolvers

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 the long, heavy pull that cocks 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). There is a rare class of revolvers, the automatic revolver, that 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 was the first commercial example, introduced in 1901. It was recoil operated, and the cylinder and barrel recoiled backwards to cock the hammer and revolve the cylinder. It was distinctive in that 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 8 shots, .455 caliber versions 6. At the time, the few available automatic pistols were larger, less reliable, and more expensive. The automatic revolver was popular when it came out, but it was quickly superseded by the creation of reliable, inexpensive automatic pistols. However, the GIGN paramilitary commandos often use S&W .357 revolvers.

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 6 or 7 cartridges, depending on the model. The company has made several versions of its "autorevolver", including longer barelled and even rifle-like variations, usually chambered for .357 Magnum ammunition, but also available in larger calibers like .44 Magnum and .454 Casull.

There is also a combat shotgun based on the automatic revolver principle, the Pancor Jackhammer. It uses a type of gas action to move the barrel forward (which unlocks it from the cylinder) and then rotate the cylinder and cock the hammer.

Rifle

A rifle is a firearm that uses a spiral groove cut into the barrel to spin a projectile (usually a bullet), thus improving accuracy and range of the projectile.  Examples of non-rifled firearms are most shotguns, and muskets. Originally, rifles were sharpshooter weapons, whilst the regular infantry made use of the greater firepower of massed muskets, which fired round balls of calibers up to 0.75 inch (19 mm). Benjamin Robins, an English mathematician, realized that an extruded bullet would retain the mass and kinetic force of a musket ball, but would slice through the air with much greater ease. The innovative work of Robins and others would take until the end of the 1700s to gain acceptance.

By the mid-19th century, however, manufacturing had advanced sufficiently that the Brown Bess was replaced by a range of—generally single-shot, breech-loading—rifles, designed for aimed, discretionary fire by individual soldiers. Then as now, rifles have a stock, either fixed or folding, which is braced against the shoulder. Until the early 20th century rifles tended to be very long—a Martini-Henry of 1890 was almost six feet (1.8 m) in length, with a fixed bayonet—and the demand for more compact weapons for cavalrymen led to the carbine, or shortened rifle. Most rifles are firearms—powered by gunpowder—although some of the earliest rifled weapons were powered with compressed air. Air rifles remain popular today, for vermin control, hunting small game and casual shooting ("plinking").

Muskets were smooth-bore, large caliber weapons using ball-shaped ammunition fired at relatively low velocity. Due to the high cost and great difficulty of precision manufacturing, and the need to load readily from the muzzle, the musket ball was a loose fit in the barrel. Consequently on firing the ball bounced off the sides of the barrel when fired and the final direction on leaving the muzzle was unpredictable. The origins of rifling are difficult to trace, but some of the earliest practical experiments seem to have originated in Europe during the fifteenth century. Archers had long realized that a twist added to the tail feathers of their arrows gave them greater accuracy. Early muskets produced large quantities of smoke and soot, which had to be cleaned from the action and bore of the musket frequently; either the action of repeated bore scrubbing, or a deliberate attempt to create 'soot grooves' might also have led to a perceived increase in accuracy, although no-one knows for sure. True rifling dates from the mid-1400s, although the precision required for its effective manufacture kept it out of the hands of infantrymen for another three and a half centuries.

Some early rifled guns were created with special barrels that had a twisted polygonal shape. Specially-made bullets were designed to match the shape so the bullet would grip the rifle bore and take a spin that way. These were generally limited to large caliber weapons and the ammunition still did not fit tightly in the barrel. Many experimental designs used different shapes and degrees of spiraling. Although uncommon, polygonal rifling is still used in some weapons today with one example being the GLOCK line of pistols.

These designs were gradually replaced with cylindrical barrels cut with helical grooves, the surfaces between the grooves being called "lands".

These designs were gradually replaced with cylindrical barrels cut with helical grooves, the surfaces between the grooves being called "lands". This innovation shortly preceded the mass adoption of breech-loading weapons, as it was not practical to push an overbore bullet down through a rifled barrel, only to then (try to) fire it back out. The dirt and grime from prior shots was pushed down ahead of a tight bullet or ball (which may have been a loose fit in the clean barrel before the first shot), and, of course, loading was far more difficult, as the lead had to be deformed to go down in the first place, reducing the accuracy due to nose deformation. Several systems were tried to deal with the problem, usually by resorting to an under-bore bullet that expanded upon firing. One of the most famous was the Minié system, which relied on a conical bullet (known as a Minié ball) with a hollow at the base of the bullet that caused the base of the round to expand from the pressure of the exploding charge and grip the rifling as the round was fired. Minié system rifles, notably the U.S. Springfield and the British Enfield of the early 1860s, featured prominently in the U.S. Civil War, due to the enhanced power and accuracy. The better seal gave more power, as less gas escaped past the bullet, which combined with the fact that for the same bore (caliber) diameter a long bullet was heavier than a round ball. Enhanced accuracy came from the expansion to grip the rifling, which spun the bullet more consistently.

Another important area of development was the way rounds were stored and used in the weapon. The Spencer repeating rifle was a breech-loading manually operated lever action rifle, that was adopted by the United States and over 20,000 were used during the Civil War. It marked the first adoption of a removable magazine-fed infantry rifle by any country. The design was completed by Christopher Spencer in 1860. It used copper rim-fire cartridges stored in a removable seven round tube magazine, enabling the rounds to be fired one after another, and which, when emptied could be exchanged for another.

As the bullet enters the barrel it screws itself into the rifling, a process which gradually wears down the barrel, and more rapidly causes the barrel to heat up. For this reason machine-guns are equipped with quick-change barrels which can be swapped every few thousand rounds, or, in earlier designs, were water-cooled. Modern stainless steel barrels for target rifles are much harder, and so wear far less, allowing tens of thousands of rounds to be fired before accuracy drops, unlike older carbon steel barrels, which were more limited, to around 1,000 shots, before the extreme accuracy faded. (Many shotguns and small arms have chrome-lined barrels to reduce wear and enhance corrosion resistance. This is rare on rifles designed for extreme accuracy as the plating process is difficult and liable to reduce the effect of the rifling.) Hardened armor-piercing bullets produce wear rapidly, which necessitates that they are encased in softer metal or Teflon.

Over the 19th century, bullet design also evolved, the slugs becoming gradually smaller and lighter. By 1910 the standard blunt-nosed bullet had been replaced with the pointed, 'spitzer' slug, an innovation which increased range and penetration. Cartridge design evolved from simple paper tubes containing black powder and shot to sealed brass cases with integral primers for ignition, whilst black powder itself was replaced with cordite, and then other smokeless mixtures, propelling bullets to higher velocities than before.

The increased velocity meant that new problems arrived, and so bullets went from being soft lead to harder lead, then to copper jacketed, in order to better engage the spiraled grooves without being "stripped" in the same way as a thread would be if subjected to extreme forces.

Rifles were initially single-shot, muzzle-loading weapons. During the 18th century, breech-loading weapons were designed, which allowed the rifleman to reload whilst under cover, but defects in manufacturing and the difficulty in forming a reliable gas-tight seal prevented widespread adoption. During the 19th century, multi-shot repeating rifles using lever, pump or linear bolt actions became standard, further increasing the rate of fire and minimizing the fuss involved in loading a firearm. The problem of proper seal creation had been solved with the use of brass cartridge cases, which expanded at the point of firing and effectively sealed the breech while the pressure remained high, then shrinking back slightly to allow for easy removal. By the end of the 19th century, the leading bolt-action design was that of Paul Mauser, whose action—wedded to a reliable design possessing a five-shot magazine—became a world standard through two world wars and beyond. The Mauser rifle was paralleled by Britain's ten-shot Lee-Enfield and America's 1903 Springfield Rifle models, the latter of which is pictured above.

The advent of mass, rapid firepower and of the machine-gun and the rifled artillery piece was so rapid as to outstrip the development of any way to attack a trench filled with rifle and machine-gun equipped soldiers. The nightmare hell of the Great War was to be the greatest vindication and vilification of the rifle as a military weapon. By the Second World War military thought was turning elsewhere, towards more compact weapons. These designs became the assault rifle, one of the most significant developments of the 20th century army.

Nonetheless, civilian rifle design has not significantly advanced since the early part of the 20th century. Modern hunting rifles have fiberglass stocks and more advanced recoil pads, but are fundamentally the same as infantry rifles from 1910. Many modern sniper rifles can trace their ancestry back for over a century; the Russian 7.62 x 54 mm bullet, used in the front-line SVD Dragunov, dates from 1891.

WW2 saw the first mass-fielding of self-loading, semi-automatic rifles including the M1 Garand. As machine-gun mechanisms became smaller, lighter and more reliable, fully-automatic rifles and assault rifles became the norm.

History of use

Muskets were used for rapid, unaimed volley fire. The average conscripted soldier could be easily trained to use them. The (muzzle-loaded) rifle was originally a sharp-shooter's weapon used for targets of opportunity and sniper fire. The adoption of cartridges and breech-loading in the 19th century was concurrent with general adoption of rifles. In the early part of the 20th century, soldiers were trained to shoot accurately over long ranges with high-powered cartridges. World War 1 Lee-Enfields rifles (among others) were equipped with long-range 'volley sights' for massed fire at ranges of up to a mile (1600 m) - individual shots were unlikely to hit, but a platoon firing repeatedly could produce an effect similar to light artillery or a machine gun - but experience in WW1 showed that long-range fire was best left to artillery and machine guns.

Up to, during, and after WW2 it has become accepted that most infantry engagements took place at ranges of less than 100 meters, and that the range and power of the large rifles was 'overkill', and the weapons were heavier than the ideal. Today, an infantryman's rifle is optimised for ranges of 300 meters or less, and soldiers are trained to deliver individual rounds or bursts of fire at these ranges. Accurate, long-range fire is the domain of the sniper and of enthusiastic target shooters. The modern sniper rifle is generally capable of accuracy better than one arcminute (300 μrad).

Rifling

Rifling refers to spiral grooves that have been formed into the barrel of a firearm. It is the means by which a firearm imparts a spin to a prjectile to gyroscopically stabilize it to improve accuracy. Most rifling is created by either cutting with a machine tool, pressed by a tool called a "button" or forged into the barrel over a "mandrel". The grooves are the spaces that are cut out, and the resulting ridges are called 'lands'. These lands and grooves can vary in number, depth, shape, direction of twist ('right' or 'left'), and 'twist rate' (turns per unit of barrel length). The spin imparted by rifling significantly improves the stability of the projectile, improving both range and accuracy. Typically in small firearms, the diameter of the bullet matches the diameter of the cirlce that encompasses the bottoms of the rifled grooves. When the cartridge is fired, the bullet is forced into the barrel and the rifling engages the bullet, deforming it somewhat. As the bullet is propelled down the barrel, it begins to spin. This rate of spin is dictated by a bullet's muzzle velocity and the twist rateof the rifling. For a given caliber, faster rates of twist are needed to stabilize longer(heavier)bullets. Smooth-bore firearms muskets require bullets that are the same diameter or less than the diameter of the bore. The energy from the discharge upsets or obdurates the bullet and expands it to form a tight seal in the musket. Rifling allows tight-fitting over-bore bullets to be squeezed into the barrel. This allows for higher pressures and longer range for rifles. A perfectly formed bullet would have the axial center of its rotating mass coincide with the axial center of its form. To the extent that these two axises differ, the flight path of the spinning bullet takes the form of an expanding cone due to gyroscopic forces. As the twist rate increases, so does the size of the "cone of inaccuracy". Therefore, increasing the twist rate beyond that required to stabilize the bullet is counterproductive.

Rimfire

A rimfire is a type of firearm cartridge. It is called a rimfire because, instead of the firing pin striking the primer cap at the center of the base of the cartridge to ignite it (as in a centerfire cartridge), the pin strikes the base's rim. The rimfire cartridge is essentially an extended and widened percussion cap which contains not only the priming compound, but also the propellant powder and the projectile (bullet). Once the cartridge has been struck and discharged it cannot be reloaded, as the head is deformed by the firing pin impact.

Rimfire cartridges are typically inexpensive, due primarily to large production quantities. A box of fifty inexpensive .22 Long Rifle cartridges typically costs less than US$1.00. Premium or match-grade .22 Long Rifle cartridges, as well as less common or out-of-production rimfire cartridges (such as the .22 Short, .22 Long, .32 Rimfire, .22 Winchester Auto, .22 WMR, and 5mm Remington) can cost substantially more.

The first rimfire cartridge was the .22 BB Cap, which used no gunpowder by relying entirely on the priming compound for propulsion. Dating back to 1857, the .22 BB Cap is essentially just a percussion cap with a round ball pressed in the front, and a rim to hold it securely in the chamber. Velocities are very low, comparable to an airgun, as the round was intended for use in indoor shooting galleries. The next rimfire cartridge was the .22 Short, developed for Smith and Wesson's first revolver; it used a longer rimfire case and 4 grains (260 mg) of black powder to fire a conical bullet. This led to the .22 Long, with a longer case and 5 grains (320 mg) of black powder. The .22 Long Rifle is a .22 Long case loaded with a longer, heavier bullet intended for better performance in the long barrel of a rifle. The .22 Long Rifle is the most common cartidge in the world. While larger rimfire calibers were made, such as the .44 Henry and the .41 Remington, the larger calibers were quickly replaced by centerfire versions, and today the .22 caliber rimfires are all that survive of the early rimfires. The early 21st century has seen a revival in interest in rimfire cartridges, with two new rimfires introduced, both in .17 caliber (4.5 mm).

Roller-delayed Blowback Action

Roller-delayed blowback is a firearm operating principle, a refined form of blowback. The main proponent of the system, Heckler & Koch, refers to it as roller-locked, although the rollers delay, rather than positively lock, the bolt. Roller-delayed blowback is not to be confused with the older roller-locked recoil operated principle, as used in the MG-42 and MG3, where the bolt is rigidly locked to the barrel as it recoils. Roller-delayed blowback was first used in experimental MG-42 derivatives and a 1945 Mauser Sturmgewehr prototype. It then made its way via the Spanish CETME to Heckler & Koch, where it was the basis for much of its product line from the 1950s onwards. The main examples are the Heckler & Koch HK G3 and HK MP5.

Semi-Automatic

A semi-automatic firearm requires a trigger pull for each round that is fired. For example, if someone were to shoot ten rounds in a semi-automatic firearm, they would need to pull the trigger ten times (once for each round fired). Compare this to a fully automatic firearm, which will continue to fire as long as the trigger is held or until it runs out of ammunition. Pistols, rifles, and shotguns can all be semi-automatic. A semi-automatic option is a common choice on selective fire firearms. Semi-automatic weapons are sometimes divided into two categories: those that fire from an open bolt and those that fire from a closed bolt. When the trigger is pulled, the open bolt flies forward, picking up a cartridge from the magazine and ramming it into the chamber and the gun fires. The closed bolt system moves the bolt forward and picks up the cartridge as the last phases of the previous cycle, and when the trigger is pulled again only the firing pin moves. The closed bolt system is generally more accurate, since the center of gravity changes relatively little. The open bolt system is almost exclusively used in submachine guns, as it also lets the barrel cool more quickly.

There is some casual dispute over the correct use of the words automatic and semi-automatic. Gun enthusiasts sometimes argue that the word automatic is often linked to fully automatic fire and that an automatic weapon is simply any weapon that chambers a new round during the extraction of the previous cartridge's casing. The term is often used to mean a self-loading semi-automatic firearm rather than a fully automatic one. One narrow definition would be that a semi-automatic firearm would thus be a weapon using the open bolt system, and the semi-automatic function is simply the removal of the case, whereas an automatic weapon would both remove the empty case and chamber a fresh cartridge. In practice, a automatic pistol usually means a self-loading semi-automatic pistol but a automatic rifle usually means one capable of fully automatic fire (as opposed to a semi-auto SLR). Both uses can be found, and the exact meaning must be determined from context.

Shotgun

A shotgun is a firearm typically used to fire a number of small spherical pellets, the shot, from a smoothbore barrel of relatively large diameter. Compared to many bullets, the energy of any one ball of shot is fairly low, making shotguns useful primarily for hunting birds and other small game, or as close-combat weapons or defensive weapons where the short range ensures that many of the balls of shot will hit the target. Ammunition for shotguns is referred to as shotgun shells, or just shells. There are also rifled barrels available for many shotguns. And different variations of ammunition. Some of which can be quite lethal. The shotgun has several advantages over a normal gun. It has enormous stopping power at short range. The wide spread of shot produced by the gun makes it easy to aim and to be used by inexperienced marksmen. Also, shot is less likely to penetrate walls and hit bystanders. It is favored by law enforcement for its low penetration and high stopping power, while many American households use it as a home defense weapon for its ease of use and wide spray.

Shotguns have also been referred to as "scatterguns", "fowling pieces" or "two-shoot guns" historically, and were used as a replacement for the blunderbuss. The first recorded use of the term shotgun was in 1776 in Kentucky. It was noted as part of the "frontier language of the West" by James Fenimore Cooper. During its long history, it has been favored by bird hunters, guards and law enforcement officials. Essentially, early muzzle-loading shotguns were identical to muskets, in that they were both smoothbore weapons that were often used to fire multiple projectiles. However, the musket was generally a longer barreled weapon than a true shotgun. The shotgun has fallen in and out of favor with military forces several times in its long history. Shotguns and similar weapons are simpler than long-range rifles, and were developed earlier. The development of more accurate and deadlier long-range rifles minimized the usefulness of the shotgun on the open battlefields of European wars. But armies have "rediscovered" the shotgun for specialty uses many times.

Snaphance

Snaphance or Snaphaunce refers to a mechanism for igniting a firearm's propellant usually in a muzzleloading gun. The mechanism, which first appeared in the late 1550s, uses flint and steel to create a shower of sparks to ignite the propellant in the gun. The flint is held in a clamp at the end of a bent lever called the cock. Upon pulling the trigger, this moves forward under the pressure of a strong spring and strikes a curved plate of hardened steel - called simply the steel, or in 17th century English dialect the frizzen - producing a shower of sparks (actually white hot steel shavings). These fall into a flash pan holding priming powder. The flash from the pan travels through the touch hole causing the main charge of gunpowder to detonate. The snaphance was a development of the earlier snaplock, the main difference being the Snaphance used an automatic pan-cover (to keep the priming dry until the exact moment of firing) similar to that used in the wheel-lock, whereas the Snaplock had a manually operated pan cover similar to that of the matchlock. The Snaphance also used the lateral sear mechanism from the wheel-lock to connect trigger to cock, and later, improved models also had a variety of safety mechanisms to prevent accidental discharge of the gun.

Sniper Rifle

Sniper rifle is a type of rifle used for engaging in the act of sniping, most purely a rifle used for shooting with great accuracy over long distances. Common features include precision manufacture, a highly reliable gun action, a precise scope or optical system, and almost always some support device for the shooter to fire from multiple positions. The need for high reliability and simplicity has resulted in many modern rifles continuing to be bolt action, though many are semi-automatic. The scope is dependent on the rifle and intended engagement distance. Some large caliber sniper rifles are sighted out to 1500 m with ultra high-magnification scopes, while rifles intended for urban combat and more limited range would use much less magnification. Many modern rifles incorporate bipods to steady the rifle for accurate shooting.

Squad Automatic Weapon(SAW)

A squad automatic weapon (SAW) is a light or general-purpose machine gun, usually equipped with a bipod and firing a 7.62 mm or 5.56 mm rifle bullet. A SAW is used to provide suppressive fire for an infantry squad or section. The basic use of this weapon is to force enemy troops to take cover and reduce the effectiveness of their return fire while friendly troops attack. This increases the likelihood of a successful attack against an enemy position. Therefore, a SAW must be light enough for an individual soldier to carry. A SAW can also be used to defend against a massed assault. However, it is not as effective in this role as a medium or heavy machine gun, as a SAW is not mounted on a tripod, and therefore cannot be set up to cover preset arcs of fire. Many SAWs (such as the RPK-74 and L86) are modified assault rifles. Most SAWs in current operation are derived from only three basic patterns: RPK, the Stoner Weapons System, or FN M249.

Doctrine

Assault rifles often provide a full automatic setting, but troops too often become excited in combat and waste large amounts of ammunition. Therefore, in many modern armies, military doctrine requires the ordinary soldier to avoid using his weapon's fully automatic mode unless defending against a mass assault or an ambush. This doctrine greatly reduces logistics loads, including combat pack weights, aerial resupply, and fuel requirements. It reduces training requirements and expense. It also extends patrol time for a typical soldier. The problem is that this doctrine provides no fire support during an assault. The SAW was invented so that a machine gun could be carried on assaults. It is a specialist weapon to avoid unnecessary use of ammunition, and reduce both the training and combat pack loads of a squad.

When applied to civil or irregular militia, this doctrine makes private purchase of ammunition affordable, and allows militia to train and operate with standard military doctrines using nonmilitary repeating rifles. In war time, such lightly equipped civil militia can be easily upgraded by distributing relatively few SAWs, one per squad, and training.

Stopping Power

Stopping power is a colloquial term used to describe the ability of a particular weapon to stop the actions of an individual by means of penetrating ballistic injury. Some theories of stopping power involve concepts such as "energy transfer" and "hydrostatic shock", although there is disagreement about the importance of these effects. Obviously, stopping power is related to the physical properties of the bullet and the effects it has on its target, but the issue is complicated and not easily studied. Critics contend that the importance of "one-shot stop" statistics is overstated, pointing out that most gun encounters do not involve a "shoot once and see how the target reacts" situation.

Submachine Gun

A submachine gun is a firearm that combines the automatic fire of a machine gun with the ammunition of a pistol, and is usually between the two in weight and size. They were first experimented with in the form of stocked pistols being turned fully automatic in the late 1800s and early 1900s. The first dedicated designs were developed in the latter stages of WWI both as improvement on earlier stocked pistols, and to offer an advantage in trench warfare. They rose to prominence as a front-line and commando weapon during WWII, and are now widely used by police and paramilitary organizations. They are ideal for close-range combat in enclosed urban environments, where a weapon's range and accuracy is less important than the ability to easily and instinctively spray a target with bullets. They were also popularized in the 1920's and 30's as weapon of choice of gangsters. Submachine guns lack long-range power and accuracy compared to higher power rifles, limiting their use in the open. Stocked automatic weapons firing pistol rounds were developed around the same time during World War One, by Italy, Germany, and the U.S.

Suppressor

A suppressor, also commonly known as a silencer is a device attached to a firearm (or sometimes an air gun) to reduce the amount of noise and flash generated by firing the weapon. It is a cylindrical-shaped metallic tube (mostly colored black) that is fitted into the barrel. The suppressor aerodynamically compresses or suppresses the motion of air in and around the barrel in which the bullet exits, causing the gunshot to be muffled or unheard. It usually has a quiet phum sound. Suppressors work much like an automotive muffler, reducing the amount of audible noise caused by the release of high pressure gas when the bullet exits the barrel. The term "silencer" is inaccurate as suppressors lessen the sound of a firearm's muzzle blast only, they cannot completely eliminate the sound of firing. The near silent suppressed firearms seen in movies and television are pure fabrication; the most effective suppressors at most reduce sound to the level of a cough, and for all but the smallest rimfire calibers, those suppressors are far larger than those depicted. Most suppressors can be removed by unscrewing it off the barrel, but some weapons have sound suppressors built into the barrel.

Early suppressors were created around the beginning of the 20th century by a number of inventors. American inventor Hiram P. Maxim is credited with inventing and selling the first commercially successful models from around 1902. The suppressor was first introduced into the United States Army Air Force before World War II. OSS (Office of Strategic Services) agents during World War II favored the newly-designed 22-caliber pistol. The addition to the sound suppressor baffle to the barrel eliminated the gunshot, and absorbed 90 percent of the noise. William Donovan, Director of the OSS, demonstrated the pistol for President Roosevelt while visiting the White House. Donovan fired ten shots into a sandbag without interrupting the President as he dictated a letter.

Legal regulation of suppressors varies widely around the world. The USA, taxes and regulates their manufacture and sale. In the United States, it is legal for an individual to possess and use a suppressor, however the BATF must approve the transfer; such transfers also require payment of a $200 tax and a significant background check. Some states go further, and explicitly ban any civilian possession of suppressors. Despite common misconception that suppressors violate the laws of war, special forces have made use of suppressed firearms in warfare worldwide since their invention. One of the more famous, and most effective, suppressed firearms was the British De Lisle carbine developed in WWII.

The suppressor is typically a cylindrical piece of machined metal that attaches to the muzzle of the pistol or rifle. Some others are designed as an integral part of the weapon, and may include an expansion chamber that partially surrounds the barrel (these are often called "telescoping" designs, a reference to old-fashioned collapsing telescopes). The suppressor reduces noise by allowing the rapidly expanding gasses from the detonation of the round to be briefly diverted or trapped inside a series of hollow chambers called baffles. Some advanced designs use baffles to shift the frequency of the remaining sound beyond the range of human hearing, further reducing noise. Other types, called "wet" suppressors or "wet cans", use a small quantity of water, oil, or grease in the first chamber to cool the powder gasses and reduce the volume. The coolant lasts only a few shots before it must be replenished, but while it lasts it can greatly increase the effectiveness of the supressor. One manufacturer claims a 30% improvement in sound suppression for "4 magazines" (32 to 68 rounds) with the addition of 5 ml of water or light oil to their suppressor. Water is most effective, due it its high heat of vaporization, but it can leak or evaporate out of the suppressor. Grease, while messier and less effective than water, can be left in the suppressor indefinitely without losing effectiveness. Oil is the least effective, as it leaks like water and is as messy as grease, leaving behind a fine mist of condensed oil after each shot. Suppressors vary greatly in size and efficiency. A type developed in the 1980s by the US Navy for 9 mm pistols is 150 by 45 mm (5.9 by 1.77 in) and is good for six shots with standard ammunition or up to thirty with low-powered, subsonic ammunition. The British Sterling suppressor is 350 mm (13.78 in) long and 75 mm (2.95 in) in diameter and will work effectively for hundreds of shots with standard ammunition. Generally the longevity of a suppressor is based on the material used for the baffles. Rubber baffles that are smaller than the bullet diameter are best, as they trap the most gas, but they wear quickly and lose effectiveness. Steel or aluminum baffles last far longer, but are less efficient to begin with. Suppressors can be improvised with any baffling material (pillow, potato, plastic bottle etc); these are only marginally useful, and often dangerous to the user. In areas where suppressors are regulated, improvised suppressors are also illegal, whether they actually reduce the sound of the firearm or not.

Suppressors are most effective when the bullet's velocity does not exceed the speed of sound. A bullet that breaks the sound barrier creates loud flight noise, or a "sonic boom". As velocity increases further beyond the speed of sound, flight noise does not increase significantly. Supersonic flight noise may be reduced somewhat by using a projectile of smaller caliber. Bullets that travel near the speed of sound are considered transonic, which means that the airflow over the surface of the bullet, which at points travels faster than the bullet itself, can break the speed of sound. Pointed b