Firearm

2007 Schools Wikipedia Selection. Related subjects: Military History and War

A firearm is a weapon that fires either single or multiple projectiles propelled at high velocity by the gases produced through 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, cordite, or other propellants. Most modern firearms (with the notable exception of smoothbore shotguns) have rifled barrels to impart spin to the projectile for improved flight stability.

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, an anti-tank gun, or a gun used in the delivery of naval gunfire. 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 rarely called "guns" in the restricted sense among specialists.

Accordingly, the term machine gun is not a misnomer. Although such firearms fire small caliber ammunition (generally 14.5 mm or smaller), they nevertheless have a flat projectile trajectory and a beaten zone, just like any other gun. Machine guns can be deployed in direct and indirect fire missions in a manner similar to artillery guns. Additionally, machine guns are crew served firearms, requiring the services of more than one crewman, just like any other gun. Generally, an automatic firearm designed for a single user is referred to as an automatic rifle. The discrimination between a machine gun and other firearms is deemed by the ATF (Bureau of Alcohol Tobacco and Firearms) as a firearm which dispenses more than one round with a single manipulation of the firing device.

In recent centuries, firearms have become the predominant weapons used by mankind. Modern warfare since the late Renaissance has relied upon firearms, with wide-ranging effects on military history and history in general. The Moors introduced firearms in Europe, when Iberia was under their rule. This created a whole new kind of battle, which molded modern-era armies.

For handguns and long guns, the projectile is a bullet or, in historical cannons, a cannonball. The projectile is fired by the burning of the propellant, but in small arms rarely contains explosives itself. For modern artillery the projectile is a shell, which nearly always contains explosives.

A distinction is sometimes made between the projectile itself as the weapon and the firearm as a weapons platform. In some cases, the firearm can be used directly as a weapon without firing a projectile, although this is virtually always a secondary method of attack. For example, arms such as rifles, muskets, and occasionally submachine guns can have bayonets affixed to them, becoming in effect a spear or pike. With some notable exceptions, the stock of a long gun can be used as a club. It is also possible to strike someone with the barrel of a hand-held gun or grasp it by the barrel and strike someone with the butt. This is called "pistol-whipping".

A problem for firearms is the accumulation of waste products from the partial combustion of propellants, metallic residue from the bullet itself, and small flecks of the cartridge case. These waste products can interfere with the internal functions of the firearm. As a result, regularly used firearms must be periodically partially disassembled, cleaned and lubricated to ensure the firearm’s reliability.

Firearms are sometimes referred to as small arms. Small arms are firearms which can be carried by a single individual. According to international conventions governing the Laws of War, small arms are defined (with some exceptions) as firearms which fire a projectile not in excess of 15mm (0.60 inches) in diameter. Small arms are aimed visually at their targets by hand using optical sights. The range of accuracy for small arms is generally limited to about one mile (1600 m), usually considerably less, although the current record for a successful Sniper attack is slightly more than 1.5 miles (2.4 km). Artillery guns are much larger than these firearms, mounted on a movable carriage, having bores of up to 18 inches (46 cm) and possibly weighing many tons. Artillery can be accurate at ranges of up to about 26 miles (42 km) and, with some notable exceptions (e.g., tank guns), are aimed using altitude/azimuth settings. Strictly speaking, such weapons are not firearms.

History

Gunpowder was invented in China around the 9th century AD. Chinese first used gunpowder in warfare in 904, as incendiary projectiles called "flying fires." "Fire lances", gunpowder-propelled arrows, were used in China from at least 1132. In 1221, cast iron bombs thrown by hand, sling, and catapult are mentioned. Somewhere around 1249, the Chinese of the Song Dynasty began to load early gunpowder in the middle of thick bamboo as a projection firearm, firing clay pellets like a shotgun. At some point in the late fourteenth century (the earliest certain example is dated 1332) they replaced the bamboo with bronze. Additionally, the Chinese and Mongols took up the use of "true" gunpowder instead of the slower-burning older mixture - which made this early cannon - known as the Huochong - more reliable and powerful. During wartime, the Chinese used the early gunpowder weapons in defence against the Mongols, and the weapon was taken up by the Mongol conquerors later. Many of the earliest weapons seem to primarily have functioned as psychological weapons, a trait gunpowder arms would keep for a long time.

During the time of the Song dynasty 11th-13th century CE, portable firearms were introduced in the form of bronze tubes (based on the firelance designs) that fired rounds iron balls.

Around the late 1400s in Europe, smaller and portable hand-held cannons were developed, creating in effect the first smooth-boore personal firearm. As the centuries progessed, these hand-held cannons evolved into the flintlock rifle, then the breech loader and finally the automatic.

Breech loaders became practical in the 1860's when metallurgy developed sufficiently that brass could be worked into "fixed ammunition". (Previously each round was custom made as needed; the shooter poured loose powder down the barrel, used leather or cloth for wadding if time allowed, selected a suitable projectile (lead ball, rocks, arrow, or nail), then seated the projectile on top of the powder charge by means of a ramrod. Performance was erratic.) Fixed ammunition combined a primer, the pre-measured charge, and the projectile in a water resistant brass "cartridge case". Most important, the soft brass expanded under pressure of the gas to seal the rear end of the barrel; which prevented the shooter from being maimed by escaping high pressure gases when he pulled the trigger.

A repeating firearm or "repeater" is a firearm that can be fired more than once between loading, more commonly known as a semi-automatic firearm if fed from a tube or magazine, or a revolver if fed from a rotating cylinder.

Early firearms had to be cocked before each shot.

Double-action revolvers could be fired two ways. You could cock it and fire it (now called "single action") or you could fire it by pulling the trigger. Single action tended to be more accurate because the trigger pull was shorter and lighter.

Self-loaders are firearms that use some of the discharge energy to reload the firearm. These are also called semi-automatics. These are typically fed from a tube or detachable magazine, also referred to as a “clip” which is actually a reference to a reloading device used in earlier firearms mostly rifles, but also in pistols.

Automatics (also called full autos, machineguns, or machine pistols) were not practical until the development of smokeless powder in the late 1800's. Black powder caused too much fouling of the mechanism to allow automatics or self-loaders to be reliable.

Small arms

Handgun

The smallest of all small arms is the handgun, which is perhaps more commonly called a " pistol". There are three common types of handguns: single-shot pistols (more common historically), revolvers, and semi-automatic pistols. Revolvers have a number of firing chambers in a revolving cylinder; each chamber in the cylinder is loaded with a single cartridge. Semi-automatic pistols have a single fixed firing chamber and a removable magazine so they can be used to fire several shots. The Italian-made Mateba revolver is a rare "hybrid," a semi-automatic revolver. Each press of the trigger fires a cartridge and rotates the cylinder so that the next cartridge may be fired immediately.

Handguns differ from rifles and shotguns in that they do not have shoulder stock and are designed to be fired with one or two hands. While the term 'pistol' defines any handheld firearm, it is common to refer to a single-shot or auto-loading handgun as a 'pistol' and a revolver as a 'revolver'.

The term 'automatic pistol' is sometimes used and is somewhat misleading in that the term 'automatic' does not refer to the firing mechanism, but rather the reloading mechanism. When fired, an automatic pistol uses recoil and/or propellent gases to automatically extract the spent cartridge and insert a fresh one from a magazine. Usually (but not always) the firing mechanism is automatically cocked as well. An automatic pistol fires one shot per trigger pull, unlike an automatic firearm such as a machine gun, which fires as long as the trigger is held down. There are, however, some fully automatic handguns (often referred to as machine pistols) so, to avoid such ambiguity and confusion, the term semi-automatic (or semiautomatic) is preferred when referring to a firearm that fires only one shot per trigger pull.

Prior to the 19th century, all handguns were single-shot muzzleloaders. With the invention of the revolver in 1818, handguns capable of holding multiple rounds became popular. At the end of the 20th century, most handguns are semi-automatic, although revolvers are still widely used. Generally speaking, military and police forces use automatic pistols due to their high magazine capacities (10, 15, 17 or, in some cases, up to 25+ rounds of ammunition) and ability to rapidly reload by simply removing the empty magazine and inserting a new one. Handgun hunters use revolvers almost exclusivly due to the fact that hunting cartridges are generally much more powerful than autopistol cartridges and the simplicity and durability of the revolver design is well-suited to them. Lawfully armed citizens carry either type, depending on personal preference.

Handguns come in many shapes and sizes. For example, the " derringer" (a generic term based on the mid-19th-century "Deringer" brand name) is a very small, short-barreled handgun, usually with one or two barrels but sometimes more (some 19th-century derringers had four barrels) that have to be manually reloaded after being fired. Carefully matched single-shot duelling pistols were used primarily in the 18th and 19th centuries to settle serious differences among "gentlemen": Alexander Hamilton and Aaron Burr are probably the most prominent Americans who used duelling pistols to settle their differences. Fully automatic, relatively easily concealed machine pistols, such as the MAC-10, GLOCK 18, and the Beretta 93R, were a late 20th-century development.

Handguns are small and usually made to be easily concealed, thus making them a very common choice for personal protection. In the military, handguns are usually issued to those who are not expected to need more potent (and more expensive) firearms, such as general and staff officers, and to those for whom there is no room for a full-sized rifle, such as armored vehicle and air crews. In this last role, they often compete with the carbine, which is also usually issued to airborne infantry because of its small size. Outside the military, handguns are the usual armament for police (in those jurisdictions where police are armed) and, where legal, for private citizens. Private citizens in most jurisdictions usually carry only concealed handguns in public except when hunting, since an unconcealed firearm would attract undue attention, and would therefore be less secure, although there are significant numbers of states in the US that continue to permit open carry of handguns. In the United States, the number of states which permit concealed carry has recently grown to over 35, and several states have well over 200,000 permit holders. Despite Second Amendment constitutional roots in the United States, the concept of citizens carrying a concealed firearm for self-defense is often a contentious political issue; see gun politics for more information.

Handguns are also used for many sporting purposes and hunting, although hunting usage is usually viewed as somewhat atypical due to the limited range and accuracy of handguns. Some hunters however do their hunting in areas of dense cover where long guns would be awkward or relish the increased challenge involved in handgun hunting due to the necessity of approaching the game animal more closely. Small-bore (e.g., .22 caliber rimfire) handguns have long been very popular for competitive target shooting, partially due to the low cost of both the firearms and the ammunition, and there is also a rapidly growing number of sporting competitions for larger calibers.

Long guns

Most modern long guns are either rifles or shotguns. Historically, a long smoothbore firearm was known as a musket. A rifle has a rifled barrel that fires single bullets, while a shotgun fires packets of shot, a single slug, a sabot, or a speciality round (tear gas, Bolo Shell, lead powder, etc.). Rifles are often built for accuracy and long range and are aimed, while shotguns are usually designed to quickly hit a moving target and are instead "pointed". Rifles have a very small impact area but a long range and high accuracy. Shotguns have a large impact area with considerably less range and accuracy. However, the larger impact area can compensate for reduced accuracy, since shot spreads during flight; consequently, in hunting, shotguns are used for flying game.

Rifles and shotguns are commonly used for hunting and often to defend a home or place of business. Usually, large game are hunted with rifles (although shotguns can be used—deer hunting with a shotgun is possible with the use of buckshot, sabots or slugs) while birds are hunted with shotguns. Shotguns are sometimes preferred for defending a home or business due to their wide impact area, multiple wound tracks (when using buckshot), shorter range, and reduced penetration of walls, which significantly reduces the likelihood of unintended harm, although the handgun is also commonly preferred.

There are a variety of types of rifles and shotguns based on the method they are reloaded. Bolt-action and lever-action rifles are manually manipulated. Manual manipulation of the bolt or the lever causes the spent cartridge to be removed, the firing mechanism recocked, and a fresh cartridge inserted. These two types of action are almost exclusively used by rifles.

Slide-action (commonly called 'pump-action') rifles and shotguns are manually cycled by shuttling the foregrip of the firearm back and forth. This type of action is typically used by shotguns, but several major manufacturers make rifles as well.

Automatic and semi-automatic rifles and shotguns both use either recoil or propellent gases to operate the firing mechanism that extracts and loads cartridges and recocks the firing mechanism. Semi-automatics employ an interrupter mechanism to only fire one shot per pull of the trigger, while full-automatics do not have such a system and fire multiple shots with a single pull of the trigger.

Both rifles and shotguns also come in break-action varieties that do not have any kind of reloading mechanism at all but must be hand-loaded after each shot. Both rifles and shotguns come in single- and double-barreled varieties; however due to the expense and difficulty of manufacturing double-barreled rifles are rare. Double-barreled rifles are typically intended for African big-game hunts where the animals are dangerous, ranges are short, and speed is of the essence. Very large and powerful calibers are normal for these types of guns.

Rifles have been in nationally featured marksmanship events in Europe and the United States since at least the 18th century, when rifles were first becoming widely available—one of the earliest purely "American" rifle-shooting competitions took place in 1775, when Daniel Morgan was recruiting sharpshooters in Virginia for the impending war with Great Britain. In some countries, rifle marksmanship is still a matter of national pride. Some specialized rifles in the larger calibers are claimed to have an accurate range of up to about one mile (1600 m), although most have considerably less effective range. In the second half of the 20th century, competitive shotgun sports became perhaps even more popular than riflery, largely due to the motion and immediate feedback in activities such as skeet, trap and sporting clays.

Machine guns

A machine gun is a fully automatic firearm used almost exclusively by the military. Although not widely fielded until World War I, early machine guns were being used by the military in the late 19th century (e.g., the Gatling gun). They are primarily defensive firearms, mainly because of the difficulties involved in moving and placing them, and their inherent lack of accuracy. In contrast, light machine guns (such as the U.S. military's M249 Squad Automatic Weapon (SAW) and the M60 machine gun, both of which are small-caliber firearms) are often wielded by a single infantryman; they provide a high rate of fire typically used as either suppressing fire or covering fire during infantry movement. Machine guns are also often mounted on vehicles or helicopters, and have often been used since World War II as offensive firearms in fighter aircraft and tanks (e.g., for air combat or suppressing fire for ground troop support).

A submachine gun is a machine gun that fires cartridges that would otherwise be used in a handgun. Probably the most well-known example of a submachine gun is the Thompson submachine gun (the "Tommy Gun" of gangster movies), which fires .45 ACP cartridges. Other well-known examples are the Israeli Uzi, the British Sten, and the German MP5, all of which implement the 9 mm Luger Parabellum, and the U.S.'s M3 Grease Gun which fires .45 ACP.

In United States law, a Machine Gun is defined (in part) by The National Firearms Act of 1934, United States code Title 26, Subtitle E, Chapter 53, Subchapter B, Part 1, § 5845 as:

"... any firearm which shoots ... automatically more than one shot, without manual reloading, by a single function of the trigger."

In the United States, purchases of machine guns manufactured after 1986 by civilians were banned by the Firearm Owners Protection Act (FOPA), passed in that year. Importation of machine guns for civilian sale in the U.S. was banned by the Gun Control Act of 1968. Machine guns manufactured prior to 1986 or imported prior to 1968 can still be legally transferred to civilians who pay a substantial tax to the BATFE and pass a background investigation. In addition, "transferable" machine guns must have been registered with the BATFE prior to 1986. Machine Gun parts kits (which do not include a functional receiver) can be transferred without restriction. Permission must be received from BATFE to move a machine gun between states.

One of the most popular, most produced and most used automatic rifles in the world is the Soviet AK-47. It served in the Soviet army as standard infantry firearm issue, as well as in many other east-block states, and is still used as standard military equipment in some former Warsaw Pact countries. As over 100 million AK-47s were manufactured, it has also become the firearm of choice worldwide for many criminal or terrorist organizations . A semi-automatic version of this firearm is available in many locales where fully automatic firearms are not available.

Loading and firing mechanisms

Muzzle-loaded Cannon

The cannon is loaded with gunpowder and the cannonball through the muzzle, while a fuse is placed at the rear. This fuse is lighted, causing the gunpowder to ignite and propel the cannonball. Most cannons were land- or ship-based guns, although hand cannons also existed. In military use, the standard cannon was tremendously powerful, while hand cannon was somewhat useless. In the 19th century, the muzzle-loaded cannon was made obsolete by the breech-loaded artillery piece with a rifled barrel.

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 (usually rifled instead of smooth-bored) are manufactured today and have many enthusiast s, 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 firearm 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 enabled a form of "automatic" fire long before the advent of the machine gun.

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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.

Wheellock

The wheellock action, a successor to the matchlock, predated the flintlock. Despite its many faults, the wheellock was a significant improvement over the matchlock in terms of both convenience and safety, since it eliminated the need to keep a smoldering match in proximity to loose gunpowder. It operated using a small wheel much like that on cigarette lighters which was wound up with a key before use and which, when the trigger was pulled, spun against a flint, creating the shower of sparks that ignited the powder in the touch hole. Supposedly invented by Leonardo da Vinci, the Italian Renaissance man, the wheel lock action was an innovation that was not widely adopted.

Flintlock

The flintlock action was a major innovation in small arms design. The spark used to ignite the gunpowder in the touch hole was supplied by a sharpened piece of flint clamped in the jaws of a "cock" which, when released by the trigger, struck a piece of steel called the " frizzen" to create the necessary sparks. (The spring loaded arm that holds a piece of flint or pyrite is referred to as a cock because of its resemblance to a rooster.) The cock had to be manually reset after each firing, and the flint had to be replaced periodically due to wear from striking the frizzen. (See also flintlock mechanism, snaphance, miquelet) The flintlock was widely used during the 18th and 19th centuries in both muskets and rifles.

Percussion cap

Percussion caps ( caplock mechanisms), coming into wide service in the 19th century, were a dramatic improvement over flintlocks. With the percussion cap mechanism, the small primer charge of gunpowder used in all preceding small arms was replaced by a completely self-contained explosive charge contained in a small brass "cap". The cap was fastened to the touch hole of the gun (extended to form a "nipple") and ignited by the impact of the gun's "hammer". (The hammer is roughly the same as the cock found on flintlocks except that it doesn't clamp onto anything.) In the case of percussion caps the hammer was hollow on the end to fit around the cap in order to keep the cap from fragmenting and injuring the shooter. Once struck, the flame from the cap in turn ignited the main charge of gunpowder, as with the flintlock, but there was no longer any need to charge the touch hole with gunpowder, and even better, the touch hole was no longer exposed to the elements. As a result, the percussion cap mechanism was considerably safer, far more weatherproof, and vastly more reliable (cloth-bound cartridges containing a premeasured charge of gunpowder and a ball had been in regular military service for many years, but the exposed gunpowder in the entry to the touch hole had long been a source of misfires). All muzzleloaders manufactured since the second half of the 19th century use percussion caps except those built as replicas of the flintlock or earlier small arms.

Cartridges

A major innovation in small arms (and light artillery) came in the second half of the 19th century when ammunition, previously delivered as separate bullets and powder, was combined in a single metallic (almost always brass) cartridge containing a percussion cap, powder, and a bullet in one weatherproof package. The main technical advantage of the brass cartridge case was the effective and reliable sealing of high pressure gasses at the breech, as the gas pressure forces the cartridge case to expand outward, pressing it firmly against the inside of the gun barrel chamber. This prevents the leakage of hot gas which could injure the shooter. The brass cartridge also opened the way for modern repeating arms, by uniting the bullet, gunpowder and primer into one assembly. Before this, a "cartridge" was simply a premeasured quantity of gunpowder together with a ball in a small cloth bag (or rolled paper cylinder), which also acted as wadding for the charge and ball. This early form of cartridge had to be rammed into the muzzleloader's barrel, and either a small charge of gunpowder in the touch hole or an external percussion cap mounted on the touch hole ignited the gunpowder in the cartridge. Cartridges with built-in percussion caps (called "primers") continue to this day to be the standard in firearms. In cartridge-firing firearms, a hammer (or a firing pin struck by the hammer) strikes the cartridge primer, which then ignites the gunpowder within. The primer charge is at the base of the cartridge, either within the rim (a "rimfire" cartridge) or in a small percussion cap embedded in the centre of the base (a "centerfire" cartridge). As a rule, centerfire cartridges are more powerful than rimfire cartridges, operating at considerably higher pressures than rimfire cartridges.

Caseless cartridges are now being explored: instead of using brass as the cartridge case, these would hold the cartridge together with paper or some other substance that is destroyed when the gun is fired, eliminating the expense of brass casings which are ejected. Caseless cartridges and the guns that would use them are still prototypes, although the idea of caseless cartridges can be traced to the musket "cartridges" widely used by the 18th-century military.

Nearly all contemporary firearms load cartridges directly into their breech. Some additionally or exclusively load from a magazine that holds multiple cartridges. A magazine is usually a box or cylinder that is designed to be reusable and is detachable from the gun. Some magazines, such as those of the Garand are internal to the firearm, and are loaded by using a clip, which is a device that looks like a rail holding the ammunition by the rim of the case. In most cases, a magazine and a clip are different in that the former's function is to feed ammunition into the firearm's breech, while the latter's is only to "charge" a magazine with fresh ammunition.

Repeating, semiautomatic, and automatic firearms

Many small arms are "single shot" firearms: i.e., each time a cartridge is fired, the operator must manually re-cock the firearm and load another cartridge. The classic single-barreled shotgun is a good example. A firearm that can load multiple cartridges as the firearm is re-cocked is considered a "repeating firearm" or simply a "repeater". The lever-action rifle of Old West fame, a pheasant-hunter's pump shotgun, and a police sniper's bolt-action rifle are good examples of repeating firearms. A firearm that automatically re-cocks and reloads the next round with each trigger pull is considered a semiautomatic firearm. An automatic (or "fully automatic") firearm is one that automatically re-cocks, reloads, and fires as long as the trigger is depressed. Many modern military firearms have a "selective-fire" option, which is a mechanical switch that allows the firearm be fired either in the semiautomatic or fully automatic mode. In the current M16A2 and M16A4 variants of the U.S.-made M16, continuous full-automatic fire is not possible, having been replaced by an automatic burst of three cartridges that makes full-automatic fire considerably more accurate.

The first "rapid firing" firearms were usually similar to the 19th-century Gatling gun, which would fire cartridges from a magazine as fast as and as long as the operator turned a crank. Eventually, the "rapid" firing mechanism was perfected and miniaturized to the extent that either the recoil of the firearm or the gas pressure from firing could be used to operate it (which made the firing mechanisms truly "automatic"). Automatic rifles such as the Browning Automatic Rifle (the "BAR") were in common use by the military during the early part of the 20th century, and automatic rifles that fired handgun rounds, known as submachine guns, also appeared in this time.

Submachine guns (such as the well-known Thompson gun) were originally about the size of carbines. Because they fire pistol ammunition, they have limited long-range use, but in close combat can spray bullets in a deadly and controllable manner due to the light recoil of the pistol ammunition. They are also extremely inexpensive and simple to build in time of war, enabling a nation to quickly arm its military. In the latter half of the 20th century, submachine guns were being miniaturized to the point of being only slightly larger than some large handguns. The most widely used submachine gun at the end of the 20th century was the Heckler & Koch MP5. The MP5 is actually designated as a "machine pistol" by Heckler & Koch (MP5 stands for Machine Pistol 5), although some reserve this designation for even smaller submachine guns such as the MAC-10, which are about the size and shape of pistols.

Nazi Germany brought the world's attention to what eventually became the class of firearm most widely adopted by the military: the so-called assault rifle (see Sturmgewehr 44). An assault rifle is usually slightly smaller than a military rifle such as the M1 Garand, the M14 or the K98k. Generally, assault rifles have mechanisms that allow the user to select between single shots, bursts of shots, or automatic fire. Moreover, assault rifles tend to incorporate military characteristics that make them look menacing: bayonet lugs, flash suppressors, and large capacity ammunition magazines. Generally, these design features are trivial in nature, and the modern military assault rifle differs very little in function from a civilian hunting rifle. Universally, civilian versions of military assault rifles are strictly semiautomatic. The cartridge fired by these rifles is midway in power between a pistol cartridge and a high-power rifle round, which gives the soldier the close-in spray ability of a submachine gun with the more precision long-range shooting of a high-power rifle round. Soviet engineer Mikhail Kalashnikov quickly adapted the concept to the AK-47, which has become the world's most widely used assault rifle. In United States, John Garand, the inventor of the M1 Garand rifle used by the U.S. military during World War II, adapted the assault rifle design to produce the M14, which was used by the U.S. military until the 1960s. The significant recoil (hence inaccuracy) of the M14 when fired in full automatic mode was seen as a problem, however, and in the 1960s it was replaced by Eugene Stoner's AR-15, which also marked a switch from the high-powered but heavy .30-caliber rifle used by the U.S. military since before World War I to the much smaller but far lighter and light recoiling (and arguably more accurate) .223-caliber rifle. The military later designated the AR-15 to the "M16". The civilian version of the M16 continues to be known as the AR-15 and looks exactly like the military version, although it lacks the mechanism that permits fully automatic fire.

Modern designs call for compact weapons retaining firepower. The bullpup design, by mounting the ammunition magazine rear of the trigger system, unifies the accuracy and firepower of the traditional assault riffle with the compact size of the submachine gun (though traditional submachine guns are still used because of the ballistic properties of the handgun ammunition that they use) ; examples are the French FAMAS or the British SA80.

New ammunition design shapes the future of firearms. Recently, smaller but powerful ammunition have been introduced, as to allow personal defence weapons to defeat infantry armours. Such designs are the basis for the Five-seveN or the FN P90. Caseless ammunition are another trend, though empeded by the large number of traditional firearms, which would make their introduction expensive (an example is the German Heckler & Koch G11). The flechette is yet another improvement over traditional ammunition, allowing for extreme penetration abilities and a very flat trajectory.