Rambo spots an unexploded British "Grand Slam" bomb from World War II and asks Schoolboy for the Claymore. Rear-safety distance has been decreased to 15 m (49 ft) and shelf life has been increased to 25 years.. In total the mine weighed about 2.43-pound (1.10 kg), and could be fitted with an optional peep sight for aiming. The M68 kit is designed to familiarize personnel with the placement and arming of a real M18 directional mine. A ferrite choke was added to prevent RF signals and lightning from triggering the mine.. Later when production was ramped up, the design was changed to flat steel scissor, folding-type legs. These performed poorly for two reasons. The initial versions of the mine used two pairs of wire legs produced from number 9 wire. Rambo spots an unexploded British "Grand Slam" bomb from World War II and asks Schoolboy for the Claymore. Some inert mines were green with a light blue band. 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. It is not clear if the United States Picatinny Arsenal 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. After a number of experiments, the engineers settled on Devcon-S steel-filled epoxy to hold the balls in place. Internally the mine consisted of a layer of 12-ounce (340 g) of C-3 explosive (the forerunner of C-4 explosive) in front of which was laid an array of 0.25-inch (6.4 mm) steel cubes. https://rambo.fandom.com/wiki/M18A1_Claymore_Mine?oldid=4907. The optimum effective range is 50 m (55 yd), at which the optimal balance is achieved between lethality and area coverage, with a hit probability of 30% on a man-sized target..  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 two feet (0.61 m) at the center of the target zone. The light blue or black plastic M33 Inert Anti-Personnel Mine is the training and practice version of the M18A1 Claymore. It was not until the improved M18A1 was developed that the Claymore became a widely used weapon. The development project completed, the Aerojet team sent the project back to Picatinny. The fragments can travel up to 250 m (270 yd). 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. Through Picatinny, the United States Army accepted the weapon into service as the M18 Claymore and approximately 10,000 were produced. The cubes were embedded in five pounds of Composition B explosive. It comes with all the components of a real Claymore kit packed in an M7 bandolier. , The original M18 mine fell far short of Picatinny's requirements. This slightly improves the fragment velocity, and protects the steel fragments from the corrosive explosive. 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.  The patent was later the subject of a civil court case between MacLeod, the Army, and Aerojet, which further developed the Claymore design. With this change, the velocity improved to 3,995 feet (1,218 m) per second. They adopted simple peep sights, which were later replaced by a knife blade sight. At its optimized range of 30 m (98 ft), the fragmentation zone is 23 m (75 ft) wide and 2 m (6.6 ft) high, with a minimum of five hits per 1 m2 (11 sq ft). The M18 was 9.25-inch (235 mm) long and 3.27-inch (83 mm) high, held in a plastic case with three folding spike legs on the bottom. Schardin also spent time researching a "trench mine" that used a directional fragmentation effect. The M18A1 Claymore Mine is a type of mine that is filled with C-4 plastic explosive. 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 metre lethal range. The M57 firing device (colloquially referred to as the "clacker") is included with each mine. It has the surface space of an average smartphone and includes a Picatinny rail for camera, laser, or other attachments. Canada fielded a weapon called the "Phoenix" landmine, which used the Misznay–Schardin effect to project a spray of 0.25-inch (6.4 mm) steel cubes towards the enemy. The Claymore fires steel balls, out to about 100 m (110 yd) within a 60° arc in front of the device. In 1954 Picatinny Arsenal issued a request for proposals (RFP) to improve the M18 as a more effective weapon. 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.