What is the difference between a rifle, SLR, submachine gun, carbine etc.?

A very common question among newbies to firearms history is "What is the difference between a rifle, a sub machine gun, a machine gun, a carbine, SLR, assault rifle etc." This post attempts to point out the differences and name famous weapons of each type.

Rifle: The name "rifle" originally comes from the fact that the barrel of such weapons is "rifled". This means that the barrel has grooves in it to impart spin to the bullet as it comes out of the barrel. This spin helps to stabilize the bullet as it travels through the air and gives it a predictable drift (e.g.) a particular rifle may fire bullets that travel 1-2 cm. to the right every 100 meters on a windless day. This feature allows the user to reasonably predict where a bullet will hit and gives the rifle its accuracy. Earlier firearms, such as muskets, had smooth barrels. Smooth bore weapons were much easier to manufacture than rifles, but lacked in accuracy, as the bullets didn't have stability in the air and deviated in a random direction from the intended target. Therefore, the standard strategy for European armies of that period was to line up men in parallel lines and tell them to all simultaneously open fire at the enemy, because almost no one could reliably hit the enemy that he was actually aiming for. This massed fire strategy worked because some enemy would be hit, even if they weren't the ones that were originally targeted. These days, most modern firearms, even small ones, such as revolvers and pistols, have rifled barrels. Therefore, in modern times, the word "rifle" by itself, implies a firearm that has a rifled barrel, is designed to be fired from the shoulder, is manually fed (i.e. after each shot fired, the user has to manually operate a lever to feed a new cartridge into the weapon) and carries a small number of cartridges internally (say 1 to 5 cartridges). Examples of modern rifles from the early 20th century would be the famous American .30-06 M1903 rifle, the British 0.303 Lee-Enfield, the Mauser M98 etc.

Assault Rifle: In the early part of the 20th century, it was realized by some military forces that most conscripted troops, who were hastily trained in wartime conditions, had less than a 50% chance of hitting a target beyond 300 meters. It was also realized that most infantry encounters occurred at less than 500 meters and rate of firepower was also an important factor in these encounters. It was therefore reasoned that there was no need to give such soldiers a weapon and ammunition capable of hitting targets at 2000+ meter ranges, since most soldiers could not hope to hit a target that far away in the first place. Instead, it was reasoned that it was better to give troops lesser powered (and therefore, smaller and lighter) ammunition to suit the actual ranges that most infantry engagements occurred at and a correspondingly lighter weapon suited to fire this ammunition. With lighter ammunition and weapon, the soldier could carry more ammunition and therefore use a weapon with a higher rate of fire. While the concept was around before World War II, it was the German StG 44 (Sturmgewehr 44) that really popularized the concept. The word Sturmgewehr was coined by Adolf Hitler and literally translates to "Storm Rifle" (the word "storm" being used in the context of "storming a castle" or "assaulting a castle") and the term "assault rifle" is actually a translation of "Sturmgewehr". Even though there were earlier weapons that could be classified as assault rifles, many historians consider the StG 44 as the first to form the concept of modern assault rifles. In these times, an assault rifle is a weapon with the following characteristics:

• Has a rifled barrel (as in the case of the rifle described in the previous section).
• Has provision to be fired from the shoulder, just like a rifle.
• Uses an intermediate powered cartridge. This means that the cartridges are smaller than those used by a regular rifle, but larger than the cartridges used by a pistol. This is one of the key differences between an assault rifle and a regular rifle.
• Is capable of selective fire modes. This means it allows the user to select between firing different numbers of shots each time the trigger is pulled. In semi automatic mode, the weapon will shoot one bullet each time the trigger is pulled. The weapon automatically chambers the next cartridge to fire, but the user needs to let go of the trigger and pull it again to shoot it. In burst mode, the weapon will fire a preset number of cartridges (say 2 or 3) with each trigger pull. In fully automatic mode, the weapon will continue to keep firing as long as the trigger is pulled and there is ammunition. The ability to switch between various modes of fire is a key feature that distinguishes an assault rifle from other types.
• Has a detachable magazine. Most modern assault rifle magazines carry 20 to 30 cartridges or so.

Examples of assault rifles include the AK-47 family, the M16 family etc.

SLR: This is an acronym for "Self Loading Rifle". The term "SLR" is usually used in commonwealth countries. This has some common features with the assault rifle described above. Like the assault rifle, this is also a weapon that has a rifled barrel and is designed to be fired from the shoulder. It also uses an intermediate powered cartridge and has a detachable magazine like the assault rifle concept. The one key difference between assault rifles and SLRs is that SLRs have only one firing mode, the "semi-automatic mode". This means that each time the user pulls the trigger, the weapon will fire only one cartridge. It will automatically eject the fired cartridge, load the next cartridge and prepare the weapon to fire, but the user has to let go of the trigger and then pull it again to fire the next cartridge. This is unlike an assault rifle, which has multiple firing modes and allows the user to switch between them. Examples of SLRs would be weapons like the American AR-15 and the Indian Ishapore 1A1 SLR. The AR-15 is a semi-automatic version of the M16 rifle and the 1A1 is a semi-automatic version of the Belgian FN FAL assault rifle.

Carbine: This is a term used for weapons that are versions of rifles or assault rifles, but with a shorter barrel and lighter weight. Carbines are bigger than pistols, but smaller versions of rifles. In the days of the Wild West, mounted riders preferred a shorter and lighter firearm because these were easier to operate than full sized firearms, when riding. In more modern times, people inside moving vehicles or in close quarter jungle combat, preferred shorter weapons for the same reason. Since carbines have shorter barrels, they lack in accuracy compared to full sized rifles or assault rifles. While they use the same cartridge as their full sized cousins, the shorter barrel also means reduced velocity bullets. Many assault rifles also come in a carbine version. For example, the American M4 (a carbine version of the M16 assault rifle), the Israeli Galil SAR (a carbine version of the Galil assault rifle), Steyr AUG carbine ( based on Steyr AUG assault rifle. The carbine form uses a 16 inch barrel, whereas the assault rifle uses a 20 inch barrel) etc.

Submachine Gun: This is a weapon that shares some similarities with assault rifles, but one key difference is that submachine guns are designed to fire pistol cartridges instead of intermediate cartridges. As a result of this, submachine guns are generally lighter and smaller than assault rifles and are about the same dimensions or smaller than carbines. Since they use pistol ammunition, they also have less recoil and therefore can be fired from either the shoulder, the hip, or even holding it like a pistol. The first weapon to use the term "submachine gun" was the famous Tommy Gun that we studied about earlier. This is a fully automatic weapon that fires .45 ACP cartridges, the same cartridge used by the Colt M1911 pistol. Another famous submachine gun from the World War II era is the British Sten gun, which is also a fully automatic weapon. Modern submachine guns such as the Heckler and Koch MP-5 are capable of selecting multiple firing modes. Submachine guns are more preferred for close-range combat in urban environments because, with lower powered pistol cartridges, there is less risk of bullets penetrating through walls and hitting innocents on the other side

Machine Gun: This generally denotes a weapon that is capable of rapid, fully automatic fire and carries a large supply of ammunition. Fully automatic fire means that the weapon will keep firing as long as the trigger is pulled and there is a supply of ammunition available to it. Most machine guns fire either full sized or intermediate sized ammunition, similar to rifles and assault rifles. Machine guns generally carry a large supply of ammunition in ammunition belts, drum magazines or box magazines. This means that they generally have hundreds of cartridges available to them, unlike the 20-30 cartridge magazines used by assault rifles. They are also generally heavier than rifles and assault rifles. Examples of machine guns would be the Gatling Gun, the Gardner Gun, the Bira gun etc. Modern machine guns include the Browning Automatic Rifle (BAR), the British Bren gun, the American Stoner 63, the Belgian FN Minimi etc.

Actions: Bolt Action

In the last couple of posts, we studied the break-open action and the sliding barrel action. Now we will study another type of action that is known for its sturdiness and is still with us. This action is the bolt action.

We actually studied the first weapon to use a bolt action a while earlier. It happens to be the Dreyse Needle Gun. This gun had a number of firsts to its name:

1. It was the first mass-produced military weapon using breech-loading technology.
2. The ammunition it used burned almost completely, so it didn't need to eject the paper casing after firing the weapon. This was a precursor to caseless ammunition.
3. It was the first bolt-action breechloading weapon.

The action was a significantly new invention in 1841, when the Dreyse needle gun was first introduced. It allowed the user to reload significantly faster than the opposition who were still using muzzle-loading weapons (almost 5 times the shooting speed). It also had the advantage that the user didn't need to stand up to reload the weapon and therefore could hide behind cover.

The basic idea of a bolt-action weapon is a manually operated bolt, which is manipulated by a handle, typically on the right side of the weapon. The handle is used to unlock the bolt and open the breech cover. The old cartridge case is then ejected from the breech chamber. The opening of the bolt may also cock the weapon in some models. Then a new cartridge is put in the chamber and the handle is then moved forward to close the bolt. In some models, the action of closing the bolt cocks the weapon. The weapon is then ready to fire.

In some models, opening the bolt causes an extractor lever to automatically pull the old cartridge case out of the chamber to eject it. The magazine has a spring that pushes a new cartridge into the chamber, when the old cartridge case is pulled out by the extraction lever. Such a mechanism is used in many bolt-action rifles, such as the Springfield M1903 rifle which carries a 5-shot magazine under it. This speeds up shooting because the user doesn't need to waste time pulling out the old cartridge or feeding a new one by hand.

Compared to other actions, the bolt-action has a few advantages. It is extremely simple to make, yet has very high accuracy. It is very cheap to manufacture and very light-weight. Best of all, it is a very strong action and can handle powerful cartridges. The only downside to it is that it doesn't support a very high rate of fire compared to some other alternatives. Since most modern military rifles are semi-automatic or selective fire weapons, they don't use this mechanism. However, the simplicity combined with the accuracy and the ability to handle high powered cartridges make it ideal to be used in sniper rifles. In fact, the bolt-action is overwhelmingly the action of choice in most of the sniper rifles used throughout the world. This mechanism is also used in many hunting rifles, where rate of fire is not as important as accuracy and power.

There are three major variants of bolt-action rifles which we will study below.

The Mauser M-98 system was first introduced in 1898 (hence M-98) with the Mauser Gewehr 98 rifle, which was used by the Germans between 1898 and 1935. This highly successful bolt-action design was later used in a lot of other rifles and is the dominant form of bolt-actions used today. In this type, the rifle is cocked when the bolt-action is opened. The Gewehr 98 has a 5-round magazine.

Click image to enlarge

The image above shows an original Mauser model from 1898. The weapon was designed with a lot of thought. The bolt handle is securely attached to the bolt and there are a couple of gas vent holes built into the bolt, so that if there is a rupture in the cartridge case or primer, the hot gases will vent out of the magazine hole instead of near the user's face. The "controlled feed" extractor claw holds on to the cartridge the moment it has fed from the magazine and holds on to it until the cartridge case is ejected. The weapon is cocked as the bolt is opened (actually, it specifically cocks as the bolt handle is rotated upwards, before pulling back to open the bolt) and the rear part of the striker protrudes from the back of the bolt, which allows one to quickly check if the rifle is cocked or not visually. The original mauser design was not given to cheap mass-production.

The cock-on-bolt-opening design was later adopted by other rifles as well, notably the Springfield M1903 (like the one shown in the picture above). The M1903 was used in the US military from 1903 all the way into the Vietnam war. The cock-on-bolt-opening design rifles are slightly slower to load than the other variant which we will study below. However, it is the more common of the two variants of bolt action and is used in nearly all modern hunting rifles today. It was also the dominant form of action used between the 1890s and the mid 1900s.

Another variant of bolt action is the cock-on-bolt-closing design. This is famously called the "Lee Enfield design" as it was first used in the Lee-Enfield rifle of 1895, otherwise known as the SMLE (Short Magazine Lee-Enfield) rifle. This rifle was heavily used in the British Commonwealth and its descendant is still used by Indian police, which makes it the longest serving bolt-action rifle model in existence.

The above is an example of a Lee-Enfield Mark I rifle. In this rifle, pushing the bolt closed cocks the rifle. This makes opening the bolt a lot faster and smoother, compared to the cock-on-opening design of the Mauser. This feature, coupled with its larger capacity 10-round magazine meant that a user could shoot 20-30 times in 60 seconds, making it the fastest bolt-action rifle of its day. The Lee Enfield rifles fire a 0.303 bullet. Note that the 0.303 bullet actually measures 0.311 inches in diameter, as we have noted previously.

The Indian Ordnance board later made a variant of this rifle called the Ishapore 2A1, which was based on the Lee Enfield Mark III rifle model.

The main difference is that the Ishapore 2A1 rifle is chambered to fire a standard NATO 7.62 x 51 mm. round. As a result of this, the steel used in this weapon is also improved to handle the higher pressures of the NATO cartridge. This rifle has the distinction of being the last bolt-action rifle designed to be used by a regular military force (other than sniper rifles, which are for special forces only). It is still used by police in various states in India. It is also popular with civilian shooters in the UK and USA.

The Lee-Enfield cock-on-closing-bolt system was also used on a number of other rifles, mostly made in the UK and other commonwealth countries.

A third variant is the Mosin-Nagant system, which was first used by the Mosin-Nagant rifle in 1895. Unlike the Mauser system, the bolt head rotates with the bolt and lugs, whereas the Mauser has the bolt head is an integral (non-removable) part of the bolt. It is also unlike the Lee-Enfield where the bolt head remains stationary and the bolt alone rotates. It is a rugged design, but is complicated. This type of bolt-action was mostly used in Russia, but one version called the M28 was manufactured by the Finns. The M28 is widely regarded as one of the finest and most accurate military rifles ever produced and was used by the most successful sniper of all time, a Finn named Simo Hayha.

There are other bolt-action systems, but never caught on as much as the above three systems.

Bolt actions are more accurate than semi-automatic rifles, which is why hunters and military snipers still use them. The reason is because when the cartridge is fired, the entire energy is devoted to propelling the bullet out of the rifle, unlike a semi-automatic or automatic weapon, where part of the energy is diverted to eject the old cartridge, auto-cock the weapon and load a new cartridge. It also has less moving parts than most other action types. The only parts that really move in a bolt-action when it is being fired are the spring and the firing pin. This simple and strong design means it can fire magnum cartridges as well. One more advantage for snipers is that it does not eject the spent round automatically, which is beneficial to the sniper because it does not give away his position and he can decide to eject the round himself when it is safe to do so. The only disadvantage is that it is slower to use than some other actions. So, while it may not be as useful to an ordinary infantryman, this action is more valuable to snipers and hunters and has thrived for these reasons even to the present day.