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The Claymore mine is a directional
anti-personnel mine Anti-personnel mines are a form of mine designed for use against humans, as opposed to anti-tank mines, which are designed for use against vehicles. Anti-personnel mines may be classified into blast mines or fragmentation mines; the latter may ...
developed for the
United States Armed Forces The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is ...
. Its inventor, Norman MacLeod, named the mine after a large medieval Scottish sword. Unlike a conventional land mine, the Claymore is command-detonated and directional, meaning it is fired by remote-control and shoots a wide pattern of metal balls into the
kill zone In military tactics, the kill zone, also known as killing zone, is an area entirely covered by direct and effective fire, an element of ambush within which an approaching enemy force is trapped and destroyed. The objective of the ambush force i ...
. The Claymore can also be victim-activated by booby-trapping it with a tripwire firing system for use in
area denial An area denial weapon is a defensive device used to prevent an adversary from occupying or traversing an area of land, sea or air. The specific method used does not have to be totally effective in preventing passage (and sometimes is not) as lon ...
operations. The Claymore fires steel balls out to about within a 60° arc in front of the device. It is used primarily in
ambush An ambush is a long-established military tactic in which a combatant uses an advantage of concealment or the element of surprise to attack unsuspecting enemy combatants from concealed positions, such as among dense underbrush or behind mo ...
es and as an anti-infiltration device against enemy
infantry Infantry is a military specialization which engages in ground combat on foot. Infantry generally consists of light infantry, mountain infantry, motorized infantry & mechanized infantry, airborne infantry, air assault infantry, and mar ...
. It is also used against unarmored vehicles. Many countries have developed and used mines like the Claymore. Examples include former Soviet Union models
MON-50 The MON-50 () is a claymore shaped (rectangular, slightly concave), plastic bodied, directional type of anti-personnel mine designed and manufactured in the Soviet Union. It is designed to wound or kill by explosive fragmentation. The mine fi ...
,
MON-90 image:Tyumen higher military command School of engineering 07.jpg, MON-90 The MON-90 is a M18A1 Claymore Antipersonnel Mine, claymore shaped, plastic bodied, directional type of anti-personnel mine designed and manufactured in the Soviet Union. It ...
,
MON-100 The MON-100 is a circular, sheet metal bodied, directional type of anti-personnel mine designed and manufactured in the early 1960s by the Soviet Union. It is designed to wound or kill by fragmentation and resembles a large bowl. Design The MON-1 ...
, and
MON-200 The MON-200 is a directional type anti-personnel mine designed and manufactured in Soviet Union. 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 ...
, as well as
MRUD The MRUD (Mina usmerena rasprskavajućeg dejstva - Directed fragmentation mine) is a Yugoslav design of plastic bodied, convex rectangular directional type anti-personnel mine designed to wound or kill by fragmentation. It is broadly similar ...
(Serbia),
MAPED F1 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 1970s. The MAPED F1 ...
(France), and Mini MS-803 (South Africa).


Description

The M18A1 Claymore mine has a horizontally convex gray-green plastic case (inert training versions are light blue or green with a light blue band). The shape was developed through experimentation to deliver the optimum distribution of fragments at range. The case has the words "FRONT TOWARD ENEMY" embossed on the front 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 C-4 or Composition C-4 is a common variety of the plastic explosive family known as Composition C, which uses RDX as its explosive agent. C-4 is composed of explosives, plastic binder, plasticizer to make it malleable, and usually a marker or o ...
behind a matrix of about seven hundred steel balls set into an epoxy resin. When the M18A1 is detonated, the explosion drives the matrix forward, out of the mine at a velocity of , at the same time breaking it into individual fragments. The steel balls are projected in a 60° fan-shaped pattern that is high and wide at a range of . 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 , with a hit probability of around 10% on a prone man-sized target. The fragments can travel up to . The optimum effective range is , 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 an M7
bandolier A bandolier or a bandoleer is a pocketed belt for holding either individual bullets, or belts of ammunition. It is usually slung sash-style over the shoulder and chest, with the ammunition pockets across the midriff and chest. Though functiona ...
("Claymore bag"). The mine is detonated as the enemy personnel approaches the killing zone. Controlled detonation may be accomplished by use of either an electrical or non-electrical firing system. 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 M4 electric firing wire on a green plastic spool is provided in each bandolier. The M57 firing device (colloquially referred to as the "clacker") is included with each mine. An M40 circuit test set is packed in each case of six mines. When the mines are daisy-chained together, one firing device can detonate several mines. The mine can be detonated by any mechanism that activates the blasting cap. There are field-expedient methods of detonating the mine by tripwire, or by a timer, but these are rarely used.


Development

The development of the M18A1 mine dates back to work done during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
. The
Misznay–Schardin effect The Misznay–Schardin effect, or platter effect, is a characteristic of the detonation of a broad sheet of explosive. Description Explosive blasts expand directly away from, and perpendicular to, the surface of an explosive. Unlike the blast ...
was independently discovered during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
by József Misznay, a Hungarian, and
Hubert Schardin Hubert Hermann Reinhold Schardin (17 June 1902 Plassow – 27 September 1965 in Freiburg im Breisgau) was a German ballistics expert, engineer and academic who studied in the field of high-speed photography and cinematography. He also was the dir ...
, a German. 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 Calord Corporation

Following the massed Chinese attacks during the
Korean War , date = {{Ubl, 25 June 1950 – 27 July 1953 (''de facto'')({{Age in years, months, weeks and days, month1=6, day1=25, year1=1950, month2=7, day2=27, year2=1953), 25 June 1950 – present (''de jure'')({{Age in years, months, weeks a ...
, Canada and the United States began to develop projects to counter them. Canada fielded a weapon called the "Phoenix" landmine, which used the
Misznay–Schardin effect The Misznay–Schardin effect, or platter effect, is a characteristic of the detonation of a broad sheet of explosive. Description Explosive blasts expand directly away from, and perpendicular to, the surface of an explosive. Unlike the blast ...
to project a spray of steel cubes towards the enemy. The cubes were embedded in of
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 and various other munitions. It was also ...
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 (about 20 to 30 meters). Around 1952 Norman MacLeod, at his company the Calord Corporation, began working on a small directional mine for use by infantry. It is not clear if the United States
Picatinny Arsenal The Picatinny Arsenal ( or ) is an American military research and manufacturing facility located on of land in Jefferson and Rockaway Township in Morris County, New Jersey, United States, encompassing Picatinny Lake and Lake Denmark. The Ar ...
took the concept from the Canadian weapon and asked Norman MacLeod to develop it, or if he developed the design independently and presented it to them. MacLeod designed a weapon called the T-48; broadly similar to the final M18A1, it lacked a number of the design details that made the M18A1 effective. Through Picatinny, the United States Army accepted the weapon into service as the M18 Claymore and approximately 10,000 were produced. It was used in small numbers in Vietnam from around 1961. It was not until the improved M18A1 was developed that the Claymore became a widely used weapon. The M18 was long and high, held in 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 of C-3 explosive (the forerunner of
C-4 explosive C-4 or Composition C-4 is a common variety of the plastic explosive family known as Composition C, which uses RDX as its explosive agent. C-4 is composed of explosives, plastic binder, plasticizer to make it malleable, and usually a marker or o ...
) in front of which was laid an array of steel cubes. In total the mine weighed about , 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 aimed in the direction of enemy approach; at that point, it was fitted with an electrical blasting cap. The mine was 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"; like the Phoenix it had an effective range of only . MacLeod applied for a patent for the mine on 18 January 1956 and was granted it in February 1961. The patent was later the subject of a civil court case between MacLeod, the Army, and Aerojet, which further developed the Claymore design. MacLeod's case collapsed when photographs of the German Trenchmine prototype were produced as evidence of
prior art Prior art (also known as state of the art or background art) is a concept in patent law used to determine the patentability of an invention, in particular whether an invention meets the novelty and the inventive step or non-obviousness criteria ...
.


Throner, Kennedy, Bledsoe, and Kincheloe at Aerojet

In 1954
Picatinny Arsenal The Picatinny Arsenal ( or ) is an American military research and manufacturing facility located on of land in Jefferson and Rockaway Township in Morris County, New Jersey, United States, encompassing Picatinny Lake and Lake Denmark. The Ar ...
issued a request for proposals (RFP) to improve the M18 as a more effective weapon. At Aerojet in the early 1950s, Guy C. Throner had independently come up with a design for a Claymore-like mine. He worked with Don Kennedy and the two men submitted a 30-page proposal in response to Picatinny's RFP. They were awarded a $375,000 development contract to improve the Claymore design. The Picatinny criteria for the weapon were as follows: * It must weigh less than * It must throw enough fragments so that at a range of it achieves a 100 percent strike rate on a target (man sized) * The fragment area must not be more than high and no more than 60 degrees wide * Fragments must have a velocity of per second providing 58
foot-pounds The foot-pound force (symbol: ftâ‹…lbf, ftâ‹…lbf, or ftâ‹…lb ) is a unit of work or energy in the engineering and gravitational systems in United States customary and imperial units of measure. It is the energy transferred upon applying a fo ...
(79
joules The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applied. ...
) of
kinetic energy In physics, the kinetic energy of an object is the energy that 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 acc ...
delivered to the target. The requirement for kinetic energy was based on the fact that 58-foot pounds is required to deliver a potentially lethal injury. Given the requirements of weight and fragment density, approximately 700 fragments were needed, with the ability to aim the mine with an accuracy of around at the center of the target zone. The team at Aerojet were given access to all previous research into directional mines, including the M18 and the Phoenix, as well as German research. Dr. John Bledsoe led the initial project. The original M18 mine fell far short of Picatinny's requirements. One of the first improvements was to replace the steel cubes with hardened 52100 alloy ball bearings. These performed poorly for two reasons. Firstly, the hardened steel balls
spall Spall are fragments of a material that are broken off a larger solid body. It can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure (as in a ba ...
ed into fragments when hit by the shock of the explosion; the fragments were neither aerodynamic enough nor large enough to perform effectively. Secondly, the blast "leaked" between the balls, reducing their velocity. A second problem was the curvature of the mine. This was determined experimentally by Bledsoe, through a large number of test firings. After Bledsoe left the project to work at the Rheem corporation, William Kincheloe, another engineer, came onto the Claymore project. Kincheloe immediately suggested using softer steel "gingle" balls, which were used in the foundry process. They did not spall from the shock of the explosive, but deformed into a useful aerodynamic shape similar to a .22 rimfire projectile. Using a homemade
chronograph A chronograph is a specific type of watch that is used as a stopwatch combined with a display watch. A basic chronograph has an independent sweep second hand and a minute sub-dial; it can be started, stopped, and returned to zero by successive ...
, the engineers clocked the balls at . The second change 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, the engineers settled on Devcon-S steel-filled epoxy to hold the balls in place. With this change, the velocity improved to . Technical challenges to overcome included developing a case to contain the corrosive C-3 explosive that would be durable 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, Aerojet had a near-final design. It was awarded a pre-production 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 (3 mm) 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, which had been used with the M18. This was found to be undesirable for a number of reasons. Bill Kincheloe came up with the idea of using a "Tiny Tim" toggle generator, of the type 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 originally intended to be a cheap
pentaprism A pentaprism is a five-sided reflecting prism used to deviate a beam of light by a constant 90°, even if the entry beam is not at 90° to the prism. The beam reflects inside the prism ''twice'', allowing the transmission of an image through a r ...
device, which would allow the user to look down from above and see the sight picture. After locating a suitably low-cost device, the engineers found that fumes from either the C-3 explosive or the cement used to glue the sight to the top of the mine corroded the plastic mirrors, rendering them unusable. They adopted simple peep sights, which were later replaced by a knife blade sight. Testing concluded that the mine was effective out to approximately , being capable of hitting 10% of the attacking force. At , this increased to 30%. The development project completed, the Aerojet team sent the project back to Picatinny. The Arsenal bid it out to various component suppliers. In 1960 it was type standardized as the M18A1. It was first used in
Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...
in the 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 choke was added to prevent RF signals and lightning from triggering the mine.


Variants


M68 Inert Training Kit

The M68 kit is designed to familiarize personnel with the placement and arming of a real M18 directional mine. It comes with all the components of a real Claymore kit packed in an M7 bandolier. The light blue or black plastic M33 Inert Anti-Personnel Mine is the training and practice version of the M18A1 Claymore. Some inert mines were green with a light blue band. It does not contain an explosive or pyrotechnic filler of any kind. It is packed in a Claymore bag with inert M10 simulated detonator cap wire, an M57 "clacker" firing control, and an M40 circuit test kit.


Mini-Multi-Purpose Infantry Munition

In early 2015, the U.S. Army began testing a smaller version of the Claymore called the Mini-Multi-Purpose Infantry Munition (M-MPIMS). It weighs and has a effective range, similar to the full-size Claymore. At its optimized range of , the fragmentation zone is wide and high, with a minimum of five hits per . It has the surface space of an average
smartphone A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
and includes a
Picatinny rail The Picatinny rail ( or ), or Pic rail for short, also known as a MIL-STD-1913 rail, 1913 rail or STANAG 2324 rail (cancelled), is a military standard rail interface system that provides a mounting platform for firearm accessories. It was ...
for camera, laser, or other attachments. The M-MPIMS is designed to be more controllable than the Claymore with less collateral damage, using an
insensitive munition Insensitive munitions are munitions that are designed to withstand stimuli representative of severe but credible accidents. The current range of stimuli are shock (from bullets, fragments and shaped charge jets), heat (from fires or adjacent ther ...
s explosive that is poured rather than packed for more uniform distribution results in more consistent blast pattern. Rear-safety distance has been decreased to and shelf life has been increased to 25 years.


International directional fragmentation AP mines

PADMINE is an anti-personnel directional fragmentation mine produced by the United Kingdom, similar to the Claymore in cosmetic design with two swivelling legs, inserted into soft-ground. Its lethality out to 50 meters arrives in the form of 650 steel balls and it is activated by remote control or trip wire. The M18 directional fragmentation anti-personnel mine, developed by Cardoen of Chile, contains 626 grams of explosives, surrounded by 607 AP fragmentation units providing a 60 degree arc of fire, with a 50-250 meters lethal range. Italy produces the DAF M6 and DAF M7 directional fragmentation mines, weighing 18 and 10 kilograms respectively, with trip wire or remote control detonation. Their appearance is similar to the Claymore mine.


National copies

A number of licensed and unlicensed copies of the mine have been produced. * : C19 Defensive and Support Mine * : M18 * : Type 66 * : (Fan Charge) VP 88, "heavier" VP 84 and VP 2010 * : IHR-60 * : VS-DAFM 7 * : P5 Mk1 * : M18A2 * : M18 Claymore * :
MON-50 The MON-50 () is a claymore shaped (rectangular, slightly concave), plastic bodied, directional type of anti-personnel mine designed and manufactured in the Soviet Union. It is designed to wound or kill by explosive fragmentation. The mine fi ...
* : M18A/M18A1 * :
MRUD The MRUD (Mina usmerena rasprskavajućeg dejstva - Directed fragmentation mine) is a Yugoslav design of plastic bodied, convex rectangular directional type anti-personnel mine designed to wound or kill by fragmentation. It is broadly similar ...
(Mina Rasprskavajućeg Usmerenog Dejstva) * : **Shrapnel mine No 2 ** Mini MS 803 mine * : **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", a smaller variant conceived for Special Forces use * : MDH-C40


See also

*
Fougasse (weapon) A fougasse is an improvised mortar constructed by making a hollow in the ground or rock and filling it with explosives (originally, black powder) and projectiles. The fougasse was used by Samuel Zimmermann at AugsburgThe Origins of Military Mi ...
* List of individual weapons of the U.S. Armed Forces *
Punt gun A punt gun is a type of extremely large shotgun used in the 19th and early 20th centuries for shooting large numbers of waterfowl for commercial harvesting operations. These weapons are characteristically too large for an individual to fire from ...
- similar killing effects at a wide area.


References


External links


International Coalition to Ban Landmines – Countries using Claymore type mines (PDF)

FM 23-23 ''ANTIPERSONNEL MINE M18A1 AND M18 (CLAYMORE)'' Field Manual
€”
GlobalSecurity.org GlobalSecurity.org is an American nonpartisan, independent, nonprofit organization that serves as a think tank, and research and consultancy group. Focus The site is focused on national and international security issues; military analysis, syste ...
{{USAF Weapons Anti-personnel mines Land mines of the United States Military equipment introduced in the 1960s