M18A1 Claymore Antipersonnel Mine
Overview
 
The M18A1 Claymore is a directional anti-personnel mine
Anti-personnel mine
Anti-personnel mines are a form of land mine designed for use against humans, as opposed to anti-tank mines, which are designed for use against vehicles...

 used by the U.S. military. It was named after the large Scottish sword
Claymore
The term claymore refers to the Scottish variant of the late medieval longsword, two-handed swords with a cross hilt, of which the guards were in use during the 15th and 16th centuries.-Terminology:...

 by its inventor, Norman A. MacLeod. Unlike a conventional land mine, the Claymore is command-detonated and directional, meaning it is fired by remote-control, shooting a pattern of metal balls into the kill zone like a shotgun.

The Claymore fires steel balls, out to about 100 meters
Metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...

 within a 60° arc in front of the device.
Encyclopedia
The M18A1 Claymore is a directional anti-personnel mine
Anti-personnel mine
Anti-personnel mines are a form of land mine designed for use against humans, as opposed to anti-tank mines, which are designed for use against vehicles...

 used by the U.S. military. It was named after the large Scottish sword
Claymore
The term claymore refers to the Scottish variant of the late medieval longsword, two-handed swords with a cross hilt, of which the guards were in use during the 15th and 16th centuries.-Terminology:...

 by its inventor, Norman A. MacLeod. Unlike a conventional land mine, the Claymore is command-detonated and directional, meaning it is fired by remote-control, shooting a pattern of metal balls into the kill zone like a shotgun.

The Claymore fires steel balls, out to about 100 meters
Metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...

 within a 60° arc in front of the device. It is used primarily in ambush
Ambush
An ambush is a long-established military tactic, in which the aggressors take advantage of concealment and the element of surprise to attack an unsuspecting enemy from concealed positions, such as among dense underbrush or behind hilltops...

es and as an anti-infiltration device against enemy infantry
Infantry
Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...

. It is also of some use against unarmored vehicles
Soft-skinned vehicle
In military science, a soft-skinned vehicle is any vehicle that is not armored. This includes trucks, motorcycles, jeeps and cars. It can also include Half-tracks and scouting vehicles if they have little or no armor....

.

Many countries use mines like the Claymore. Examples include former Soviet Union models MON-50
MON-50
The MON-50 is a claymore shaped , plastic bodied, directional type of anti-personnel mine designed and manufactured by Russia. It is designed to wound or kill by explosive fragmentation...

, MON-90
MON-90
The MON-90 is a claymore shaped, plastic bodied, directional type of anti-personnel mine designed and manufactured in Russia. It is designed to wound or kill by fragmentation...

, MON-100
MON-100
The MON-100 is a circular, sheet metal bodied, directional type of anti-personnel mine designed and manufactured in Russia. It is designed to wound or kill by fragmentation and resembles a large bowl.-Design:...

, MON-200
MON-200
The MON-200 is a directional type anti-personnel mine designed and manufactured in Russia. It is an enlarged version of the MON-100 mine.Because of its large size, this directional blast mine can also be used against light-skinned vehicles and helicopters....

, MRUD (Serbia), MAPED F1 (France)
MAPED F1 (France)
The MAPED F1 is a claymore shaped plastic bodied directional anti-personnel mine which is designed to wound or kill by fragmentation. It has been the standard directional anti-personnel mine of the French army since the late 70s...

, and Mini MS-803 (South Africa).

Description

The M18A1 Claymore mine consists of a horizontally convex green plastic case (inert training versions are blue). The shape was developed through experimentation to deliver the optimum distribution of fragments at 50 m (54.7 yd) range. The case has the words "Front Toward Enemy" embossed on the front surface of the mine. A simple open sight on the top surface allows for aiming the mine. Two pairs of scissor legs attached to the bottom support the mine and allow it to be aimed vertically. On both sides of the sight are fuse wells set at 45 degrees.

Internally the mine contains a layer of C-4 explosive behind a matrix of about seven hundred 1/8 in steel balls (about as big as #4 birdshot) set into an epoxy resin.

When the M18A1 is detonated, the explosion drives the matrix forward, out of the mine at a velocity of 1200 m/s, at the same time breaking it into individual fragments. The steel balls are projected in a 60° fan-shaped pattern that is 6.5 feet high and 50 m (54.7 yd) wide at a range of 50 m (54.7 yd). The force of the explosion deforms the relatively soft steel balls into a shape similar to a .22 rimfire projectile. These fragments are moderately effective up to a range of 100 m (109.4 yd), with a hit probability of around 10% on a prone man-sized 1.3 square foot (0.120773952 m²) target. The fragments can travel up to 250 m (273.4 yd). The optimum effective range is 50 m (54.7 yd), at which the optimal balance is achieved between lethality and area coverage, with a hit probability of 30% on a man-sized target.

The weapon and all its accessories are carried in a bandolier
Bandolier
A bandolier or a bandoleer is a pocketed belt for holding ammunition. It was usually slung over the chest. In its original form, it was common issue to soldiers from the 16th to 18th centuries. This was very useful for quickly reloading a musket....

. An instruction sheet for the weapon is sewn inside the cover of the bandolier.

Ideally, the mine is detonated as the enemy approaches the killing zone 20 to 30 m (21.9 to 32.8 yd), where maximum casualties can be inflicted. Controlled detonation may be accomplished by use of either an electrical or non-electrical firing system
Detonator
A detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common....

. When mines are employed in the controlled role, they are treated as individual weapons and are reported in the unit fire plan. They are not reported as mines; however, the emplacing unit must ensure that the mines are removed, detonated, or turned over to a relieving unit. The M57 Firing Device (colloquially referred to as the "clacker") is included with each mine. When the mines are daisy chain
Daisy chain (electrical engineering)
In electrical and electronic engineering a daisy chain is a wiring scheme in which multiple devices are wired together in sequence or in a ring...

ed together, one firing device can initiate several mines.

The mine can be detonated by any mechanism that activates the blasting cap. Field-expedient methods of detonating the mine by tripwire, or even by a timer, exist, but are rarely used.

Development

The development of the M18A1 mine dates back to work done during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. The Misznay-Schardin effect
Misznay-Schardin effect
The Misznay–Schardin effect, or platter effect, is a characteristic of the detonation of a broad sheet of explosive. The explosive blast expands directly away from the surface of an explosive...

 was independently discovered during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 by Misznay, a Hungarian
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...

, and Dr. Hubert Schardin
Hubert Schardin
Hubert Schardin Hermann Reinhold was a German ballistics expert, engineer and academic who studied in the field of Time-lapse photography and high-frequency Cinematography....

, a German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

. When a sheet of explosive detonates in contact with a heavy backing surface (for example, a metal plate), the resulting blast is primarily directed away from the surface in a single direction. Schardin spent some time developing the discovery as a side-attack anti-tank weapon, but development was incomplete at the end of the war. Schardin also spent time researching a "trench mine" that used a directional fragmentation effect.

Norman MacLeod and Explosive Research Corporation

Following the massed Chinese attacks during the Korean War
Korean War
The Korean War was a conventional war between South Korea, supported by the United Nations, and North Korea, supported by the People's Republic of China , with military material aid from the Soviet Union...

, Canada and the United States began to develop projects to counter them. Canada fielded a weapon called the "Phoenix" landmine that used the Misznay-Schardin effect
Misznay-Schardin effect
The Misznay–Schardin effect, or platter effect, is a characteristic of the detonation of a broad sheet of explosive. The explosive blast expands directly away from the surface of an explosive...

 to project a spray of 0.25 inches (6.4 mm) steel cubes towards the enemy. The cubes were embedded in five pounds of Composition B
Composition B
Composition B, colloquially "comp B", is an explosive consisting of castable mixtures of RDX and TNT. It is used as the main explosive filling in artillery projectiles, rockets, land mines, hand grenades, sticky bombs and various other munitions...

 explosive. It was too large to be a practical infantry weapon and was relatively ineffective with a maximum effective range of only 20 to 30 yards (20 to 30 meters).

Around 1952 Norman MacLeod at his company the Explosive Research Corporation began working on the concept of a small directional mine for use by infantry. It is not clear if Picatinny took the concept from this Canadian weapon and asked Norman MacLeod to develop it; or if he came up with the idea independently and presented it to them. MacLeod came up with a design, the T-48 that was broadly similar to the final M18A1, although it lacked a number of the design details that made the M18A1 effective. It was accepted into Army service as the M18 Claymore and approximately 10,000 were produced. It was used in small numbers in Vietnam from around 1961, but it was not until the arrival of the improved M18A1 that it became a significant weapon.

The M18 was 9.25 inches (235 mm) long and 3.27 inches (83.1 mm) high with a plastic case with three folding spike legs on the bottom. An electrical blasting cap for triggering the mine was inserted through a small hole in the side. Internally the mine consisted of a layer of 12 ounces (340.2 g) of C-3 explosive (the forerunner of C-4 explosive) in front of which was laid an array of 0.25 inches (6.4 mm) steel cubes. In total the mine weighed about 2.43 pounds (1.1 kg), and could be fitted with an optional peep sight for aiming. It lacked the later version's iconic "FRONT TOWARD ENEMY" marking. The mine was planted in the ground using its three sharp legs and was aimed in the direction of enemy approach and then fitted with an electrical blasting cap. The mine was then triggered from a safe position, preferably to the side and rear.

The mine was barely more than a prototype and was not considered a "reliable casualty producer" with an effective range like the Phoenix of only 90 feet (30 m).

MacLeod applied for a patent for the mine on 18 January 1956 and was granted it in February 1961. The patent was later the source of a civil court case between MacLeod, the Army, and Aerojet who proceeded to develop the design further. MacLeod's case collapsed when photographs of the German Trenchmine prototype were produced as evidence of prior art
Prior art
Prior art , in most systems of patent law, constitutes all information that has been made available to the public in any form before a given date that might be relevant to a patent's claims of originality...

.

Kennedy, Throner, Bledsoe, and Kincheloe at Aerojet

In 1954 Picatinny Arsenal
Picatinny Arsenal
The Picatinny Arsenal is an American military research and manufacturing facility located on a lot in northern New Jersey near Lake Denmark. The Arsenal is the headquarters of the United States Army Armament Research, Development and Engineering Center...

 issued a request for proposals (RFP) aimed at improving the M18 into a more effective weapon. Guy C. Throner working at Aerojet
Aerojet
Aerojet is an American rocket and missile propulsion manufacturer based primarily in Rancho Cordova, California with divisions in Redmond, Washington, Orange, Gainesville and Camden, Arkansas. Aerojet is owned by GenCorp. They are the only US propulsion company that provides both solid rocket...

 had independently come up with a design for a Claymore-like mine in the early 1950s. Seeing the RFP and working with Don Kennedy they submitted a 30 page proposal to Picatinny and were awarded a $375,000 development contract to improve the design. Picatinny criteria for the weapon were as follows
  1. It must weigh less than 3.5 pounds (1.6 kilograms)
  2. It must throw enough fragments so that at a range of 55 yards (50 m) it achieves a 100 percent strike rate on a 1.3 square foot (0.120773952 m²) target (man sized)
  3. The fragment area must not be more than 8 feet (2.4 m) high and no more than 60 degrees wide
  4. Fragments must have a velocity of 4000 feet (1,219.2 m) per second providing 58 foot-pounds (79 joules) of kinetic energy
    Kinetic energy
    The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...

     delivered to the target.

The requirement for kinetic energy came from the fact that 58 foot pounds is the amount of kinetic energy required to deliver a potentially lethal injury. Given the requirements of weight, and fragment density required this dictated using approximately 700 fragments, and being able to aim the mine with an accuracy of around two feet (0.6 m) at the center of the target zone. The team at Aerojet were given access to all previous research into the directional mine, including the M18 and the Phoenix mine, as well as German research. Dr. John Bledsoe led the initial project.

The original M18 mine fell far short of requirements. One of the first improvements was to replace the steel cubes with 7/32 in hardened 52100 alloy ball bearings. These performed poorly for two reasons. First, the hardened steel balls spall
Spall
Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure...

ed into fragments when hit by the shock of the explosion; the fragments were neither aerodynamic enough nor large enough to perform effectively. Additionally the blast "leaked" between the balls, reducing their velocity.

A second problem to be addressed was the curvature of the mine. This was determined experimentally by Bledsoe, through a large number of test firings. Bledsoe left the project to work at the Rheem corporation, and another engineer, William Kincheloe came onto the project.

Kincheloe immediately came up with the suggestion to use softer 1/8 in steel "gingle" balls that were used in the foundry process. The softer balls did not spall when struck by the shock from the explosive, instead they deformed into a useful aerodynamic shape similar to a .22 rimfire
.22 Long Rifle
The .22 Long Rifle rimfire cartridge is a long established variety of ammunition, and in terms of units sold is still by far the most common in the world today. The cartridge is often referred to simply as .22 LR and various rifles, pistols, revolvers, and even some smoothbore shotguns have...

 projectile. Using a homemade chronograph
Gun chronograph
A gun chronograph is an instrument used to measure the velocity of a projectile fired by a gun.-History:Around 1800, the ballistic pendulum was used to measure the momentum of the projectile fired by a gun; dividing the momentum by the projectile mass gives the velocity.An early chronograph that...

 these were clocked at 3775 feet (1,150.6 m) per second. The second optimization was to use a poured plastic matrix to briefly contain the blast from the explosive, so that more of the blast energy was converted into projectile velocity. After a number of experiments they settled on Devcon-S steel filled epoxy
Epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....

 to hold the balls in place. With this improvement, the velocity improved to 3995 feet (1,217.7 m) per second.

There were still a number of technical challenges to overcome, including the development of a case that would be able to contain the corrosive C-3 explosive, and be tough enough to withstand months of field handling in wide temperature ranges. Using dyes to test various plastics for leaks, they found a suitable plastic called Durex 1661½ which could be easily molded into a case.

By the spring of 1956 they had a near-final design, which was awarded a preproduction contract for 1,000 M18A1 claymores designated T-48E1 during testing.
The initial versions of the mine used two pairs of wire legs produced from number 9 wire. Later when production was ramped up the design was changed to flat steel scissor, folding-type legs.

Early pre-production mines were triggered using a battery pack that was used with the M18, however this was undesirable for a number of reasons. Bill Kincheloe came up with the idea of using a "Tiny Tim" toggle generator used with a number of navy rockets. Originally an aluminum box was used to hold the generator. Later a Philadelphia company, Molded Plastic Insulation Company, took over the manufacture of the firing device for the first large scale production run producing a plastic device.

The sighting for the device was also originally intended to be a cheap pentaprism
Pentaprism
A pentaprism is a five-sided reflecting prism used to deviate a beam of light by 90°. The beam reflects inside the prism twice, allowing the transmission of an image through a right angle without inverting it as an ordinary right-angle prism or mirror would.The reflections inside the prism are not...

 device, that would allow the user to look down from above and see the sight picture. After finding a suitably low-cost device, it was found that fumes from either the C-3 explosive or the cement used to adhere the sight to the top of the mine corroded the plastic mirrors, rendering them unusable. In the end simple peep sights were adopted, which was later replaced by a knife blade sight.

Testing concluded that the mine was effective out to approximately 110 yards (100.6 m), being capable of hitting 10% of the attacking force. At 55 yards (50.3 m) this increased to 30%. The development project completed, the Aerojet team sent the project back to Picatinny, where it was bid out to various component suppliers. It was type standardized as the M18A1 in 1960, seeing first active service in Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...

 in spring or early summer 1966.

Minor modifications were made to the mine during its service. A layer of tinfoil was added between the fragmentation matrix and the explosive. This slightly improves the fragment velocity, and protects the steel fragments from the corrosive explosive. A ferrite
Ferrite bead
A ferrite bead is a passive electric component used to suppress high frequency noise in electronic circuits. It is a specific type of electronic choke. Ferrite beads employ the mechanism of high dissipation of high frequency currents in a ferrite to build high frequency noise suppression devices...

 choke was added to prevent RF signals and lightning from triggering the mine.

Ottawa treaty

The use of this mine is permitted by the Ottawa Treaty
Ottawa Treaty
The Ottawa Treaty or the Anti-Personnel Mine Ban Convention, officially known as the Convention on the Prohibition of the Use, Stockpiling, Production and Transfer of Anti-Personnel Mines and on their Destruction, aims at eliminating anti-personnel landmines around the world. , there were 158...

 as it is most often command-detonated.

National copies

A number of licensed and unlicensed copies of the mine have been produced.: M18: Type 66: Viuhkapanos VP 88 and "heavier" VP 84: IHR-60: VS-DAFM 7: P5 Mk1: M18A2 : M18 Claymore: MON-50
MON-50
The MON-50 is a claymore shaped , plastic bodied, directional type of anti-personnel mine designed and manufactured by Russia. It is designed to wound or kill by explosive fragmentation...

: Shrapnel mine No 2:
K440, slightly smaller than the Claymore with 770 fragments.
KM18A1:
FFV-013
Försvarsladdning 21
LI-12/Truppmina 12: M18 AP Mine: Arms-Tech MM-1 "Minimore"
MM-1 minimore
The MM-1 "Minimore" is a small-sized version of the M18A1 claymore mine, currently manufactured by Arms-Tech Ltd. of Phoenix, Arizona. The company literature refers to it either as the "MM-1 Directional Command Detonated Mine" or as the "Minimore-1 Miniature Field-Loadable Claymore Mine". The MM-1...

, a smaller variant conceived for Special Forces
Special forces
Special forces, or special operations forces are terms used to describe elite military tactical teams trained to perform high-risk dangerous missions that conventional units cannot perform...

 use: MDH-C40: MRUD
MRUD
The MRUD is a plastic bodied, convex rectangular directional type Anti-personnel mine designed to wound or kill by fragmentation. It is broadly similar to the M18A1 Claymore mine....

(Mina Rasprskavajuća Usmerenog Dejstva)

See also


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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