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C-4 or Composition C-4 is a common variety of military plastic explosive.
The term composition is used for any stable explosive, and "Composition A" and "Composition B" are other known variants. C-4 is 1.34 times as explosive as trinitrotoluene (TNT).
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Composition
C-4 is made up of explosives, plastic binder, plasticizer and, usually, marker or taggant chemicals such as 2,3-dimethyl-2,3-dinitrobutane (DMDNB) to help detect the explosive and identify its source.
As with many plastic explosives, the explosive material in C-4 is RDX (cyclonite or cyclotrimethylene trinitramine) which makes up around 91% of the C-4 by weight. The plasticizer is diethylhexyl or dioctyl sebacate (5.3%) and the binder usually is polyisobutylene (2.1%).
Another plasticizer used is dioctyl adipate (DOA). A small amount of SAE 10 non-detergent motor oil (1.6%) is also added. C-4 detonates with a pressure wave of about 8,040 m/s (26,400 ft/s), or 28,900 km/h (18,000 mph).
C-4 is manufactured by combining RDX slurry with binder dissolved in a solvent. The solvent is then evaporated and the mixture dried and filtered. The final material is an off-white solid with a feel similar to modelling clay. The plasticized form of RDX, composition C-4, contains 91% RDX, 2.1% polyisobutylene, 1.6% motor oil, and 5.3% 2-ethylhexyl sebacate.
The Demolition charge M183 is used primarily in breaching obstacles or demolition of large structures where large charges are required (Satchel Charge). The charge assembly M183 consists of 16 block demolition charges M112, four priming assemblies and carrying case M85. Each Priming assembly consists of a five-foot length of detonating cord assembled with two detonating cord clips and capped at each end with a booster. The components of the assembly are issued in the carrying case. The demolition charge M112 is a rectangular block of Composition C-4 approximately 2 inches (51 mm) by 1.5 inches (38 mm) and 11 inches (280 mm) long, weighing 1.25 lb (0.57 kg). When the charge is detonated, the explosive is converted into compressed gas. The gas exerts pressure in the form of a shock wave, which demolishes the target by cutting, breaching, or cratering.
Using explosives provides the easiest and fastest way to break the frozen ground. Composition C-4, tetrytol, and TNT are the best explosives for use in northern operations because they retain their effectiveness in cold weather. Dig a hole in the ground in which to place the explosive and tamp the charge with any material available to increase its effectiveness. Either electric or nonelectric circuits may be used to detonate the charge. For a "foxhole", 4.6 kg (10 lb) of explosive will usually be sufficient. Another formula is to use 2 pounds (1 kg) of explosive for every 30 cm (1 ft) of penetration in frozen ground.
Advantages
A major advantage of C-4 is that it can be molded into any desired shape. C-4 can be pressed into gaps, cracks and voids in buildings, bridges, equipment or machinery. Similarly, it can easily be inserted into empty shaped-charge cases of the type used by military engineers, pioneers and special forces. C-4 is incredibly stable, and can only be detonated by combined extreme heat and pressure or an electric jolt.
International usage
British Military plastic explosive is referred to as PE4. Like C-4, it is an off-white colored solid and its explosive characteristics are nearly identical to C-4. The only difference between C-4 and PE4 is the type and proportion of plasticizer used. Very similar to the British PE4 is the Italian military plastic explosive referred to as T4.
Because C-4 burns slowly when it is ignited with a flame rather than detonated with a primary explosive, soldiers during the Vietnam War era would sometimes use small amounts of C-4 as fuel for heating rations while on long patrols.1 While many soldiers used C-4 safely in this manner, there are several anecdotes about soldiers attempting to put out the fire by stomping on it — causing it to detonate.citation needed
Michael Herr in Dispatches, his book about the Vietnam War, relates that a soldier would occasionally ingest C-4 from a claymore mine in order to cause temporary illness and be sent on sick leave. Although the ruse might work with an inexperienced commander, experienced officers were usually aware of the trick and would keep the man on board.citation needed
C4 has become the most portrayed conventional explosive in several motion pictures and video games (e.g. Die Another Day - opening sequence detonation of briefcase of diamonds).citation needed
References
External links
- Commercial C4 supplier information, showing characteristics and cost per kilo
- HowStuffWorks article
- Autobiographical page of a Vietnam veteran Includes mention of C-4 used for demolition.
