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.
History
Early history of the carbine: 1800s and earlier
The carbine was originally a lighter, shorter weapon developed for cavalry soldiers, for whom a full-length musket or rifle was too heavy and awkward to fire from horseback. Carbines were usually less accurate and powerful than the longer rifles of the infantry, due to a shorter sight plane and lower velocity of bullets fired from the shortened barrel. With the advent of fast-burning smokeless powder, the velocity disadvantages of the shorter barrels became less of an issue (see internal ballistics). Eventually, the use of horse-mounted cavalry would decline, but carbines continued to be issued and used by many who preferred a lighter, more compact weapon even at the cost of reduced long-range accuracy and power. A shorter weapon was more convenient when riding on horses, but it was also more convenient when riding in a truck, armored personnel carrier, helicopter or aircraft, and also when engaged in close-range combat.
During the 1800s carbines were often developed separately from the infantry rifles, and in many cases did not even use the same ammunition, which made for supply difficulties. In the late 1800s it became common for a number of nations to make bolt-action rifles in both full-length and carbine versions. One of the most popular and recognizable carbines was the Winchester lever-action carbine, with several versions using revolver cartridges. This made it an ideal choice for cowboys and explorers, who could carry a revolver and a carbine, both using the same ammunition. Another well-known carbine was the Spencer repeating carbine, which was one of the first firearms to use a self-contained metallic cartridge.
Shorter rifles, shorter carbines: World War I and World War II
In the decades preceding World War I, the standard battle rifle used by armies around the world had been growing shorter, either by redesign or by the general issue of carbine versions instead of full-length rifles. For example, the Russian Model 1891 rifle with a 31.5 inch (800 mm) barrel was shortened to 28.75 in. (730 mm) in 1930, and to 20 in. (510 mm) in 1938; the German Mauser 98 rifles went from 29 in. (740 mm) in 1898 to 23.6 in. (600 mm) in 1935 as the Karabiner Kurz (K98k), or "short carbine". The barrel lengths in rifles used by the United States did not change between the bolt-action M1903 rifle of World War I and the World War II M1 Garand rifle, but then the 24 in. (610 mm) barrel on the M1903 was short for its day. The US M1 Carbine was more of a traditional carbine in that it was significantly shorter and lighter, with an 18 in. barrel (460 mm), than the M1 Garand rifle. The M1 Carbine was not a shorter version of the M1 Garand, but a wholly different design firing a smaller, less-powerful cartridge as was common in the 1800s.
Post-World War II
Based on the combat experience of WWII, the criteria used for selecting infantry weapons began to change. Unlike previous wars, which were often fought mainly from fixed lines and trenches, WWII was a highly mobile war, and often fought in cities, forests, or other areas where mobility and visibility were restricted. In addition, improvements in artillery made moving infantry in open areas even more suicidal then it had been.
The majority of enemy contacts were at ranges of less than 300 meters (325 yards), and the enemy was exposed to fire for only short periods of time as they moved from cover to cover. Most rounds fired were not aimed at an enemy combatant, but instead fired in the enemy's direction to keep them from moving and firing back (see suppressive fire). These situations did not require a heavy rifle, firing full-power rifle bullets with long-range accuracy. A less-powerful weapon would still produce casualties at the shorter ranges encountered in actual combat, and the reduced recoil would allow more shots to be fired in the short amount of time an enemy was visible. The lower-powered round would also weigh less, allowing a soldier to carry more ammunition. With no need of a long barrel to fire full-power ammunition, a shorter barrel could be used. A shorter barrel made the weapon weigh less and was easier to handle in tight spaces, and was easier to shoulder quickly to fire a shot at an unexpected target. Full-automatic fire was also considered a desirable feature, allowing the soldier to fire short bursts of three to five rounds, increasing the probability of a hit on a moving target.
The Germans had experimented with selective-fire carbines firing rifle cartridges during the early years of WW2. These were determined to be less than ideal, as the recoil of full-power rifle cartridges caused the weapon to be uncontrollable in full-automatic fire. They then developed an intermediate-power cartridge round, which was accomplished by reducing the power and the length of the standard 7.92 x 57 mm rifle cartridge to create the 7.92 x 33 mm Kurz (Short) cartridge. A selective-fire weapon was developed to fire this shorter cartridge, eventually resulting in the Sturmgewehr 44, literally "Storm Rifle", later translated as "assault rifle". After WWII, the USSR would adopt a similar weapon, the well-known AK-47, which became the standard Soviet infantry weapon.
Although the NATO countries did not adopt an intermediate-power round, they continued the trend toward shorter and lighter magazine-fed battle rifles. NATO adopted the 7.62 x 51 mm NATO round, along with several rifles such as the FN FAL and M14.
By the 1960s NATO had adopted the 5.56 x 45 mm NATO cartridge. This round was even lighter and smaller than the Soviet AK-47 cartridge, but possessed higher velocity. In U.S. service, the M16 assault rifle replaced the M14 as the standard infantry weapon, although the M14 continued in use by designated marksmen.
The trend was continuing; lighter carbines were being adopted as the standard infantry long rifle. What changed was that a certain amount of soldiers were now retaining longer range weapons, designated marksmen. Development of lighter assault rifles continued, with even lighter carbines keeping pace. At the same time the infantry switched to 5.56 mm weapons, carbines like the AK74SU (which fired a Warsaw pact 5.45 x 39 mm round) and CAR 15 were being developed.
Modern history
Carbine use in contemporary military forces
By the 1990s, the US had adopted the M4 Carbine, a derivative of the M16 family which was lighter and shorter (in overall length and barrel length) subsequently resulting in reduced power. In addition, due to the development of body armor, support personnel required a compact weapon with more stopping power than the traditional pistol, leading to the development of the personal defense weapon, or PDW, which uses rounds that have better ballistics than simple pistol rounds but less power and range than full rifle rounds. Examples include the FN P90 and HK MP7. Whether these ultra-light weapons will receive widespread adoption has yet to be seen; in particular, it is questionable whether their stopping power is adequate. The cartridge used by the FN P90, the 5.7 x 28 mm, for example, fires a 30 grain (1.9 g) armor piercing bullet at velocities of around 2300 ft/s (700 m/s). This gives similar ballistics to the high velocity loadings in the .22 Winchester Magnum Rimfire round, which is generally considered wholly inadequate for defensive use. The H&K MP7 fires an even smaller 4.6 mm round with ballistics similar to the .22 WMR derived .17 Hornady Magnum Rimfire. The small diameter rounds enable the projectile to travel at the high velocity needed to penetrate kevlar armor, as a light weapon with sufficient energy to push a large caliber bullet through the armor would have prohibitive recoil. The small bullets, however, do not have much wounding power. They are generally designed to tumble after penetration, and while that works in theory, other tumbling rounds such as the 5.56 x 45 mm and the 5.45 x 39 mm have shown erratic performance in the field (see below).
Meanwhile, many armies are experiencing a backlash against carbines and lighter rifles in general, and are equipping more soldiers with higher power rifles. While firing more smaller bullets makes it easier to hit a target, and is good for beginner marksmen, it offers little to more advanced marksman. In addition, the additional range of the heavier weapons has proven to be necessary in open environments such as deserts. As a result, the focus on more highly trained soldiers equipped with, for example, 7.62 mm NATO firing rifles has increased somewhat.
Special operations forces
One bastion of the carbine which is unlikely to be unseated is the Special Operations Forces of the world. Because of the need to perform fast, decisive operations, a pistol is viewed as not having enough power. A pistol is conversely very light, and aids in the speed of the operator. Consequently, carbines have gained wide acceptance among SOCOM and other communities. An example of this would be the Springfield Armory SOCOM 16, which is a 16 in (406 mm) barreled carbine chambered in .308 Winchester. With a composite stock and lighter parts, as well as increased sight aperture or ACOG, the rifle maintains a high degree of accuracy for close quarters battle, as well as being serviceable to ranges up to 400 yards (370 m). The rifle maintains light weight, and has far superior stopping power to most pistol cartridges. Additionally, with 20 and 30 round magazines, the firepower is dramatically preferable to a pistol.
Personal defense weapons
In both civilian use and among the military's lighter armored soldiers, it is common to use a carbine. However, due to some of the reasons mentioned above, such as muzzle blast and recoil, these carbines are generally chambered in lighter rounds than some of their heavier (or shorter) counterparts. Due to the low wounding power of a single round, personal defense weapons depend on high volumes of fire for effectiveness. This may make such carbines successful in military use. In civilian use, where fully automatic fire is impractical or illegal, and shot placement is more critical, acceptance may be lower, as a pistol may be easier to fire effectively for a less-trained person.
Future acceptance and use
To what extent armies will adopt even lighter carbines, and to what extent they will be avoided has yet to be seen entirely. It is likely that harder hitting, or at least higher penetrating weapons will become more common, due to a rise in use of body armor making weaker weapons ineffective. Stacked against this is mainly the amount of urban warfare that is required, which favours lighter carbine weapons.
The modern usage of the term carbine covers much the same scope as it always had, of lighter weapons (generally rifles) with barrels of less than about 18 inches (460 mm). These weapons can be considered carbines, while rifles with barrels of 20 inches (510 mm) or more are generally not considered carbines unless specifically named so, and depending on the weapon power. Modern carbines are chambered in calibers from pistol calibers to full power rifle cartridges usually up to, but not including, the high velocity magnum rifle cartridges. In the more powerful cartridges, the short barrel of a carbine has significant disadvantages in velocity, and the high residual pressure when the bullet exits the barrel results in substantially greater muzzle blast. Flash suppressors and muzzle brakes are common solutions to this problem, which may ease their acceptance.
Usage
Pistol caliber carbines
One of the more unusual classes of carbine is the pistol caliber carbine. These first appeared soon after metallic cartridges became common. These were developed as "companions" to the popular revolvers of the day, firing the same cartridge but allowing more velocity and accuracy than the revolver. These were carried by cowboys, lawmen, and others in the Old West. The classic combination would be a Winchester lever action carbine and a Colt revolver in .44-40 or .45 Colt. Modern equivalents also exist, such as the Ruger Police Carbine, which uses the same magazine as the Ruger pistols of the same caliber. Beretta has also recently released a pistol caliber carbine that shares magazines with Beretta pistols, which might indicate that there is a growing demand for these companion carbines.
The primary advantage of a pistol caliber carbine, other than the usually-added buttstock or shoulder rest for increased accuracy, is the fact that in general a longer barrel will yield higher projectile velocity. This results in greater stopping power and increased ability to penetrate body armor. Additionally, many pistol calibers, such as .45 ACP, have much heavier projectiles, such as 230 grain (15 g), than rifles do, 55 grains (3.6 g) being common in 22-caliber rounds like .22-250 and .223.
Ultra carbines
Firearms with shoulder stocks and barrels less than 16 in (406 mm) in length are classified as "short barreled rifles" (under the US National Firearms Act or NFA), and are sometimes restricted in the same way that sawed off shotguns and machine guns are. Because of this, rifles with barrels of less than 16 in (406 mm), or pistols with shoulder stocks, are rare. A "kit" exists which will convert a GLOCK pistol to a carbine, which is particularly interesting because the GLOCK 18 fully automatic pistol.
Air carbines
In the world of airguns, there is a small but growing class of what are also called "ultra carbines", that have extremely short barrels. These may be rifles with barrels cut down to as short as 8 inches (203 mm), or pistols converted into carbines with the addition of a shoulder stocks. These are generally not restricted legally in the same way some firearms are.
Other carbines
Another class of carbine is a semi-automatic version of a submachine gun, with an extended barrel, just over 16 inches (406 mm) long, which will escape ban by some "assault weapon" legislation. While functionally identical to other carbines, these are banned in some places as "assault weapons" based on their cosmetic similarity to submachine guns. However, they may not accept certain parts (such as magazines or collapsing stocks) from the submachine guns they resemble. These are a popular compromise for (American) shooters who would like to own a submachine gun but cannot due to local restrictions or the prohibitive cost of buying a civilian legal submachine gun (since the end of the Clinton assault weapons ban, this has become less prohibitive). While these submachine gun lookalikes are acceptable for use for self defense, the media generally portrays them as being used for violent crime. As such, this may make them a poor choice for a personal defense weapon. This does not deter many of the more vocal proponents of personal defense firearms, who typically recommend a pistol and a higher power weapon, like a carbine or a shotgun.
In some historical cases the term machine carbine was the official title for sub-machine guns. Examples are the Sten and Owen guns. Equally to confuse the non-automatic version of the Sterling sub-machine gun was also a "Carbine".