Mortar (weapon)

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US soldier loading a M224 60-mm mortar.

French 120 mm MO-120-RT-61 mortar

French 120 mm mortar

American soldiers firing a 120 mm mortar

A mortar is a muzzle-loading indirect weapon that fires shells at low velocities, short ranges, and high-arcing ballistic trajectories. It typically has a barrel length less than 15 times its caliber.

A mortar is relatively simple and easy to operate. A modern mortar consists of a tube which gunners drop a shell into. A firing pin at the base of the tube detonates the propellant and fires the shell.

These attributes contrast with the mortar's larger siblings, rifled howitzers and field guns, which fire at higher velocities, longer ranges, flatter arcs, and sometimes, direct fire.

In the 19th and early 20th centuries very heavy immobile siege mortars were used, of up to one metre calibre.

A mortar can also be a launcher for fireworks, a hand-held or vehicle-mounted projector for smoke shells or flares, or a large grenade launcher.

Light and medium mortars are portable, and usually used by infantry organizations. The chief advantage a mortar section has over an artillery battery is its small numbers, mobility and the ability to engage targets in the defilade with plunging fires. It is able to fire from the protection of a trench or defilade. In these aspects the mortar is an excellent infantry support weapon, as it can be transported over any terrain and is not burdened by the logistical support needed for artillery.

There are also heavy mortars of 120 mm to 240 mm calibre. These weapons are usually towed or vehicle-mounted, sometimes breech-loaded, and normally employed by infantry units attached to battalion through division level. Even at this large size, mortars are simpler and less expensive than comparable howitzers or field guns.

A mortar can be carried by one or more people (larger mortars can usually be broken down into components), or transported in a vehicle. An infantry mortar can usually also be mounted and fired from a mortar-carrier, a purpose-built or modified armoured vehicle with a large roof hatch. A heavy mortar can be mounted on a towed carriage, or permanently vehicle-mounted as a self-propelled mortar.

An unusual support weapon is the Soviet/Russian 2B9 Vasilek 82 mm automatic mortar, also manufactured by the People's Republic of China's Norinco as the Type W99 mortar. This is a fully-automatic weapon, capable of a high rate of fire. It can also be used in a direct fire mode, and can fire a HEAT round used against light armoured vehicles.

1 Design
- 1.1 Spigot mortar
- 1.2 Other Advantages
2 History
3 See also
4 References
5 External links

[edit] Design

Most modern mortar systems consist of three main components: a tube or barrel, a base plate, and a bipod.

Modern mortars normally range in caliber from 60 millimeters (2.36 inches) to 120 millimeters (4.72 inches) however, aberrations both larger and smaller than these specifications have been produced. An example of the smaller scale is the British 51 mm light mortar which is carried by an individual and consists of only a tube and a base plate. Conversely, a large abnormality is the Soviet 2S4 M1975 "Tyulpan" (tulip tree) 240-mm self-propelled mortar.

Smaller mortars (up to 81 mm) are commonly used and transported by infantry based mortar sections as a substitute for, or in addition to, artillery.

Ammunition for mortar systems generally come in two main varieties: fin-stabilized and spin-stabilized. The former have short fins on their posterior portion that control their path in flight. The latter use spin (similar to a thrown American Football) to balance and control the mortar shell. These rounds can either be illumination (infrared or visible illumination), smoke, or high explosive.

Spin-stabilised rounds require a rifled barrel. Since mortars on the whole are breach-loaded, the mortar shell has a pre-engraved band, called an opturator, that engages with the rifling of the barrel. The increase in accuracy is at a cost in loading time and having to account for drift, a peculiarity of rifled systems that causes the round to "drift" perpendicular to the spin axis; this Magnus effect is what makes it possible for pitchers to throw curve balls.

Mortars come in a variety of calibres. The French 81 mm mortar became standard for many countries. The Soviets ingeniously took tactical advantage of this. They standardized an 82 mm mortar for their armies. Hence, troops using Soviet mortars could use mortar ammunition of other countries found on the battlefield, albeit with less accuracy, while their own would be too large for their opponents. This advantage was used during the Vietnam War and at other times.^{[citation needed]}

[edit] Spigot mortar

Spigot mortars are a particular type of mortar consisting of a (mostly) solid rod or spigot, and a hollow tube in the projectile into which the spigot fits, inverting the normal tube mortar arrangement. At the top of the tube in the projectile is a cavity containing propellant such as cordite. There is usually a trigger mechanism built into the base of the spigot, with a long firing pin running up the length of the spigot activating a primer inside the projectile and firing the propellant charge.

The advantage of a spigot mortar is that the firing unit (baseplate and spigot) is smaller and lighter than a conventional mortar of equivalent payload and range. It is also somewhat simpler to manufacture.

The disadvantage is that the mortar projectile requires additional material to contain the propellant gases during firing. While most mortar shells have a streamlined shape towards the back that naturally fits a spigot mortar application well, using that space for the spigot mortar tube takes volume and mass away from explosive warhead payload and fragmentation mass of the projectile. If a soldier is carrying only a few projectiles, the projectile weight disadvantage is not significant. However, the weight of a large quantity of the heavier and more complex spigot projectiles offsets the weight saved due to the spigot mortar being lighter than a conventional mortar.

A near silent mortar can be made using the spigot principle. Each round has a closely fit but moveable plug in the tube that fits over the spigot. When the round is fired, the projectile is pushed off the spigot, but before the plug clears the spigot, the plug is caught by a narrowing at the base of the tube. This traps the gases from the propelling charge and hence the sound of the firing. Post WW II the silent Belgium Fly-K spigot mortar was accepted into French service as the TN-8111.

Spigot mortars are generally out of favor in modern usage, replaced by small conventional mortars.

Military applications of spigot mortars include

Anti-tank launchers
- The Blacker Bombard and PIAT antitank launcher used by Britain in WW II utilized a spigot mortar type of launcher.

Anti-submarine launchers
- The Hedgehog launcher, used from the deck of a ship, fired a circular pattern of antisubmarine projectiles into the sea ahead of the ship. A sinking projectile detonated if it struck a submarine, and the pattern was such that any submarine partly in the landing zone of the projectiles would be struck one or more times.

Georgian-era portable French Mortar.

Mallet's Mortar with 36 inch shells which would have contained 480 lb (217 kg) of gunpowder.

An 1832 "Monster Mortar" invented by Henri-Joseph Paixhans.

Nonmilitary applications include use of small-caliber spigot mortars to launch lightweight, low-velocity foam dummy targets used for training retriever dogs for bird hunting. Extremely simple launchers use a separate small primer cap as the sole propellant (similar or identical to the cartridges used in industrial nailguns).

[edit] Other Advantages

An additional advantage of the mortar is its ability to drop shells on targets close to the mortar, due to the "lobbing" nature of the ballistics. This feature also makes it possible to launch attacks from positions lower than the target of the attack. For example, conventional long-range artillery could not shell a city centre 1 km away and at an elevation disadvantage of 30 meters (100 feet), but shelling the city by mortars would be possible.

[edit] History

Mortars have existed for hundreds of years, first finding usage in siege warfare. However, these weapons were huge, heavy, iron monstrosities that could not be easily transported. Simply made, these weapons were no more than iron bowls truly reminiscent of the kitchen and apothecary mortars wherefrom they drew their name. An early transportable mortar was invented by Baron Menno van Coehoorn (Siege of Grave, 1674). Coehorn mortars, of approximately 180 lbs weight, were used by both sides during the American Civil War. During the Russo-Japanese War of 1904–1905, Leonid Gobyato for the first time applied deflection from closed firing positions in the field and designed together with General Roman Kondratenko the first mortar that fired navy shells. However, it was not until World War I and the Stokes trench mortar devised by Sir Wilfred Stokes in 1915, that the modern mortar transportable by one person was born. The Germans also developed a series of trench mortars or Minenwerfer in calibres from 7.58 cm to 25 cm.

Extremely useful in the muddy trenches of Europe, mortars were praised because of their shells high angle of flight. A mortar round could be aimed to fall directly into trenches where artillery shells, due to their low angle of flight, could not possibly go. Modern mortars have improved upon these WW I designs even more, offering a weapon that is light, adaptable, easy to operate, and yet possesses enough accuracy and firepower to provide the infantry with quality close fire support against soft and hard targets more quickly than any other means.

The largest mortars ever developed were the French "Monster Mortar" (developed by Henri-Joseph Paixhans in 1832), "Mallet's mortar" (developed by Woolwich Arsenal, London in 1857) and the "Little David" (developed in the United States for use in World War II). Each weapon had a caliber of 36 inches (915 mm); only the "Monster Mortar" was used in action (at the Battle of Antwerp in 1832).^[1]

Improvised "homemade" mortars have been used by terrorist groups (usually to attack fortified military installations) in some countries.