This article will look at the various types of guns; ‘gun’ referring to both the direct-fire artillery piece (as used in military parlance) and the more general ‘firearm’ (in common usage).

    1. Rifles

A rifle is a firearm characterised by a long barrel with spiral or polygonal grooves on the inner wall (known as rifling, hence the term ‘rifle’), a buttstock to be braced against the shoulder for aiming and control, and the use of ammunition cartridges with a conical or spire-point bullet (known as spitzer) with a cartridge case length of at least 34mm. Rifles are designed to deliver accurate, direct fire at mid- to long range (where the target is beyond visual range of the naked eye). They can be categorised into two distinct groups: Bolt-action (whereby the firearm’s cycling mechanism is manually operated by unlocking, opening, closing and locking a bolt) and Auto-loading (cycling mechanism is automatically operated by the firing of a cartridge in the firearm’s chamber).

1a. Sniper Rifle: A sniper rifle is a rifle designed for highly-precise, long range shooting, usually of personnel or materiel (hardware and equipment). Compared to other rifles, it has a heavier barrel, bipod or other kind of support, and telescopic sight. Its effective range can vary from 0.5km up to 2.5km. A sniper rifle is intended to be shot from a concealed position. Precision is rated in MOA (minute of angle), where a shot group at 91m (100yd) will have a dispersion of about 25.4mm (1 inch). Sniper rifles usually shoot 1 MOA or below (called ‘sub-MOA’). A sniper is well versed in field-craft, battlefield surveillance, and is able to calculate distance, elevation, windage, temperature and atmospheric pressure with the use of Mil reticles in the rifle’s telescopic sight (Mil-Dots, Mil-Hashes, similar stadiametric markings). The rifle is usually a bolt-action rifle and usually holds the least number of rounds of any other type of rifle, as per the motto: “One Shot, One Kill”. Some sniper rifles are semi-automatic, and typically trade off some precision at extended range for a higher rate-of-fire and magazine capacity; one such sniper rifle is the M110 Semi-Automatic Sniper System (SASS). A sniper rifle’s bullet is spitzered and may be filled with an armor-piercing penetrator or incendiary mixture for engaging enemy materiel such as Light Armoured Vehicles. Some sniper rifles can be modified to become anti-materiel rifles using cartridges above 7.62mm (.30) calibre. Some long range rifle cartridges like the 8.6x70mm (.338) Lapua Magnum intend to fill the anti-personnel and anti-materiel roles simultaneously. The predecessors of these anti-materiel rifles were anti-tank rifles. An example of a modern sniper rifle is the Accuracy International L115A1 Arctic Warfare Magnum.

1b. Designated-Marksman Rifle (DMR): A designated-marksman rifle is designed for accurate, rapid fire at ranges up to 1km. It is usually an accurized battle rifle with an optical sight, but purpose-built DMRs are also available. It is semi-automatic only and may have an adjustable stock. A designated-marksman operates in a squad or section, and does not fill the role of a sniper as he is not well trained in field-craft and has little to no reconnaissance skills. An example of a modern designated marksman rifle is the M39 Enhanced Marksman Rifle (upgraded M14 DMR, used by the US Marine Corps).

1c. Battle Rifle: A battle rifle is either a bolt-action or auto-loading rifle that fires full-power cartridges (.30 caliber with 50mm case length or more). A battle rifle has more range and accuracy as compared to an assault rifle and has been the standard-issue firearm for most militaries up until the later half of the 20th century since the invention of the modern cartridge. A battle rifle’s effective range is usually between 500m to 1km, depending on calibre and design. Although battle rifles are becoming obsolete and being replaced with smaller assault rifles, there are some armed forces that still use battle rifles. An example of a revolutionary battle rifle is the Heckler & Koch roller-delayed blowback G3, derived from the Sturm-Gewehr 45(M).

1d. Assault Rifle: An assault rifle is a selective fire rifle that fires an intermediate cartridge from a magazine. Its effective range varies from 300m to 600m, depending on calibre, and usually less than 640m. It is carried by a single soldier and is supplied en masse. It usually can be fitted with optical sights, lasers, night vision sights, flashlights, suppressors, grenade launchers etc. It is durable and lightweight and can endure a substantial amount of punishment. Shorter and more compact versions of assault rifles are called carbines. A prime example of an assault rifle is the Sturm-Gewehr 44, which was the world’s first assault rifle.

    2. Machine Guns

A machine gun is a fully automatic firearm characterised by a long and heavy barrel, capable of high rates-of-fire for long periods of time, with a relatively large ammunition capacity (by means of belted links, high-capacity magazines or similar feed devices). Due to their nature as tactical suppression weapons, they often feature a quick-change barrel or a cooling system to prevent the barrel from overheating and jamming the gun. Most machine guns are classified as crew-served weapons, and are usually operated by a gunner and an assistant who feeds the rounds into the gun via belted links.  A machine gun with multiple barrels revolving about a central axis is called a Gatling gun.

2a. Heavy Machine Gun (HMG): A HMG is a machine gun that fires large-calibre cartridges (projectile diameters up to 14.5mm and case lengths up to 114mm) which produce excessive amounts of recoil, enough to destroy a jeep’s suspension if undampened. As such, Heavy Machine Guns can only be mounted onto static firing positions (fortifications such as bunkers, pillboxes) or mobile platforms (vehicles such as aircraft, tanks, watercraft), and are unable to be carried by a single man. Many HMGs are used as Anti-Aircraft (AA) Guns or light armour penetration weapons against jeeps and some Armoured Personnel Carriers. An example of a Heavy Machine Gun is the CIS 50.

2b. General-Purpose Machine Gun (GPMG): A General-Purpose Machine Gun is a machine gun that fires full-power cartridges from belted links, and is one that can be mounted onto fortifications, vehicles, or carried by a two-man crew or an individual infantryman. The mounted variant of such a machine gun is usually referred to as a Medium Machine Gun (MMG), while the man-portable variant is known as a Light Machine Gun (LMG). An example of a General-Purpose Machine Gun is the M60.

2c. Squad/Section Automatic Weapon (SAW): A SAW is a fully-automatic or select-fire light machine gun which fires intermediate cartridges from either a belt or magazine feed. A SAW is carried and fired by an individual soldier, without the need to set up a firing position using a separate bipod or tripod. The ammunition used is the same as assault rifles which infantrymen have been issued with, enabling the sharing of rounds in a squad or section. It is man-portable and can be set up in a short amount of time as compared to other automatic support weapons. An early version of the SAW is the automatic rifle. A modern SAW is the M249.

2d. Submachine Gun (SMG): A submachine gun is a compact, fully-automatic or select-fire machine gun which fires pistol cartridges from a magazine. The SMG is designed to be carried and fired by a single man in closed-quarters scenarios like the interior of a building. Unlike it’s larger and heavier cousins, the submachine gun is not designed for long periods of fully-automatic fire, and does not feature a quick-change barrel or stabilising mount. An example of an SMG is the H&K MP5.

2e. Personal Defense Weapon (PDW): A Personal Defense Weapon is a compact, lightweight, select-fire firearm that is similar in size to submachine guns but usually fires armor-piercing rounds. It has greater accuracy than most submachine guns and can use specialised cartridges like the 4.6x30mm or 5.7x28mm. An example of a modern PDW is the Fabrique Nationale P90.

    3. Handguns

A handgun is a small, lightweight firearm (able to be carried in a single hand) characterised by a short barrel length, lack of buttstock, and the use of ammunition cartridges with a case length of 33mm and below. Handguns are designed to be fired at close ranges (no longer than 50m in theory, not more than 15m in practical use) and are designed to be stowed in a holster worn on the shooter’s body. Handgun trigger mechanisms come in three main types: Single-Action (SA), Double-Action (DA), and Striker. Single-Action triggers perform the sole function of releasing the hammer from the spring tension to fire a round; this gives it the lightest and shortest trigger pull. Double-Action triggers perform the dual role of bringing the hammer from rest to cock it under spring tension and releasing it to fire; this gives it an exceptionally heavy and long trigger pull. Striker triggers have a spring-loaded firing pin (striker) in place of a hammer, and performs a part of Double-Action triggers by cocking the striker fully and releasing it to fire; this gives it a fairly light and moderately long trigger pull. Some handguns are compact enough to be concealed in an inside-the-waistband holster, while others require a dedicated duty holster in which to carry them in. Most handguns are defensive weapons, typically intended to be drawn from the holster in a last resort situation wherein a hostile individual (or several hostiles) needs to be stopped with the use of deadly force.

3a. Pistol: A pistol is a handgun with a chamber that is part of the barrel, as opposed to a revolver where there is no actual chamber and a gap between the barrel and feed (cylinder). A pistol holds its cartridges in a magazine which fits into the pistol grip. The pistol has a slide which acts as a bolt for cycling the rounds each time the trigger is pulled and the slide will lock open after the last round is fired. To reload the pistol, release the magazine and insert a fresh one into the magazine well, then rack the slide forward with the slide release or manually by hand. Although a pistol can be fired single-handed, professional shooters fire with both hands on the grip to ensure maximum stability and therefore, accuracy. An example of a modern pistol is the Walther PPQ.

3b. Revolver: A revolver is a repeating handgun that has a cylinder for holding the cartridges, thus having no magazine. A revolver is simpler than a semi-automatic pistol as it doesn’t have a slide to cycle the rounds, it doesn’t use any gases from the fired round and doesn’t jam as much because of lesser parts. A revolver can be single-action or double-action, meaning that the hammer either has to be recocked by hand or is cocked by the trigger after each shot respectively. A revolver usually holds 6 rounds in the cylinder (hence the name “six shooters”) and the barrel is usually longer than those found on a semi-automatic pistol. However, there are modern compact revolvers that have shorter barrel lengths of around 3-4 inches and special features such as integral hammer intended for concealed carry. An example of a revolver is the Smith & Wesson Model 29 (renowned .44 Magnum revolver used by Dirty Harry).

4. Shotgun: A shotgun is a smoothbore firearm (like the musket) that fires multiple pellets called shots. The most recognised feature of a shotgun is the pump, which is a cycling mechanism located on the tube magazine just below the barrel, serving as a manually-operated bolt. However, there are also shotguns that use other operating mechanisms for cycling, such as lever-action, recoil or even gas-operated reloading. There are several different types of projectiles that shotguns can fire: three main projectiles are Birdshot, Buckshot and Slugs. Birdshot is the type of the smallest calibre shots, used for hunting birds (hence the name) and other animals. Buckshot pellets are larger than Birdshot and they are used in the military or police. Slugs are the largest projectile that a shotgun can fire; they are basically a large lead bullet which may or may not be rifled. As opposed to multiple sub-calibre shots, a slugshell contains a single full-calibre slug. Shotgun calibre is not calculated in metric nor inches, but in gauges. The gauges are always denoted in order of inversely proportionate calibres: the largest diameter shell is 8 gauge (21.2mm), the most popular 12 gauge (18.5mm), 20 gauge (15.6mm), 28 gauge (13.9mm), 36 gauge (12.8mm) and the smallest 40 gauge (12.4mm). The most similar rifle caliber is the 12.7x99mm. An example of a modern shotgun is the Auto-Assault 12.

    5. Shell-firing Weapons

Shell-firing weapons fire payload-carrying projectiles instead of solid bullets or shots, known as shells. The payload carried in these shells are often explosive, armor-piercing, incendiary, illuminating, or a combination of such payloads. Shells rely on a fuze (triggering mechanism) to initiate the delivery of the payload (like the firing pin in a firearm being released by the sear to strike the cartridge’s primer). The fuze can be initiated by physical (impact/contact with a surface), chemical (mixing of reactive substances within the shell), and/or electronic (electric current with a timer or sensor) means.

5a. Grenade Launcher: A grenade launcher is a firearm that launches a grenade from its barrel. It can be a standalone firearm or one that is attached to a rifle. Early grenade launchers were single-shot or pump-action, like the M79. Then came the automatic grenade launchers that were designed like machine guns capable of delivering hundreds of rounds per minute. The most widely-used caliber is 40mm, including the 40x46mm low velocity and 40x53mm high velocity grenades. The purpose of a grenade launcher is to enable the soldier to hit both personnel and armoured targets with grenades more accurately at longer ranges. There are also “smart” grenades which can be set to explode at a certain time and place, and even after impact (these are known as “delayed airburst munitions”), such as the 40x46mm grenades developed by ST Kinetics. An example of a modern grenade launcher is the Milkor six-barreled Multiple Grenade Launcher.

5b. Auto-cannon: An auto-cannon is a fully-automatic firearm that fires shells 20mm or larger in diameter from a high-capacity feed, similar to that on a machine gun. An auto-cannon is mounted on a turret or tripod and requires several men to operate. It is usually mounted on vehicles and aircraft as it is light enough and provides a huge amount of firepower. A single-barreled autocannon that is cycled by an external motor or chain rather than gases from the cartridges being fired is called a chain gun. An example of an auto-cannon is the Bofors 40mm (used extensively in World War 2 as an Anti-Aircraft gun).

5c. Howitzer: A howitzer is an artillery piece that has a relatively short barrel compared to other artillery. A howitzer has a high trajectory of fire and moderately light weight. Typically, howitzers are self-propelled, meaning that the howitzer is part of an armoured vehicle and can ‘shoot and scoot’. An example of a howitzer is the 87.6mm Ordnance QF 25 (used in Singapore for 21-gun salutes).

5d. Mortar: A small, man-portable or vehicle-transported, ultra-light muzzle-loaded artillery piece that has the highest ballistic trajectory of any artillery. A mortar has the shortest barrel of any artillery piece. It usually requires only 2 men to operate it. Mortar calibres vary from 60mm up to 120mm, catorgorised as Light, Medium or Heavy Mortars. When the gunner drops the mortar bomb down the muzzle, the primer hits the firing pin fixed at the base of the barrel, which causes the self-contained propellant to detonate and launch the bomb skywards on its high arc towards the target. A modern mortar is the 81mm M252.

5e. Tank Gun: A tank gun is a large-calibre high velocity smoothbore gun that is the main armament of a tank. The gun calibres are usually 75mm (~3-inch) and larger, with the standard modern calibre being 120mm (4.72-inch). A tank gun has to be able to defeat any ground target at long range (2km and above) and is always employed as a direct-fire weapon as opposed to indirect fire artillery pieces. It will have a bore evacuator (also known as a ‘fume extractor’) on the barrel to prevent toxic gases from entering the turret after firing. A tank gun usually fires a Kinetic-Energy round, which is a large-caliber Armour-Piercing (AP) shot. The KE round doesn’t contain any explosives and is suited for medium ranges. For long range engagements, a High-Explosive Anti-Tank (HEAT) round is used as its effectiveness is not dependent on the shell’s initial velocity. An example of a modern tank gun is the 120mm Rheinmetall L55.