What is “C-4 Explosive?” Can Terrorists Obtain It?

Plastic explosives are more complicated than what you have seen in the movies…


Picture the typical heist movie: The gang hunched around the bank vault door, applying “plastic explosives” around the lock. Then, everyone takes cover, and the door is blown open — BAM!

So, what is this “plastic explosive” everyone uses?

C-4 (Composition 4) is one of a variety of “plastic bonded explosives” (PBX). C-2 and C-3 were used during WWII, while C-4 was invented in 1956 by the Phillips Petroleum Company. Coating the explosive chemical makes it less sensitive to shock and heat, plus it makes the explosive easy to mold into differing shapes.

A soldier uses a knife to shape a block of plastic explosive.

Interestingly, since C-4 is so stable, lighting it with a match just makes it burn slowly. Even shooting it won’t set it off. Only using a detonator such as a blasting cap (itself a small explosive) can supply the needed shock to trigger the C-4 explosive.

Once detonated, the chemical reaction releases gases which expand at over 27,000 feet (5 miles!) per second, thus applying a huge amount of force. At this rate, it’s impossible to outrun the explosive (despite all the action movies you've seen!).

Military-issued bricks of C-4, weighing in at about 1.25 pounds and 2” x 2” x 11” in size, can demolish a truck. To sever an 8-inch steel beam would require up to 10 pounds of C-4.

Can Terrorists Obtain It?

Terrorist have used C-4 for decades. For example, in 1996, 5,000 pounds of C-4 was used to blow up the Khobar Towers military housing complex in Saudi Arabia, killing 20 U.S. Air Force service-members. Later, 700 pounds were used in 2000 in an attack on the USS Cole, killing 17 U.S. Navy sailors. C-4 was also been used to build improvised explosive devices (IED’s) by Iraqi insurgents towards the end of the Iraq War.

The USS Cole.

Even nation-states have used it for what some call “terrorist acts.” In 1987, two North Korean agents planted a C-4 bomb in an overhead storage bin aboard Korean Air flight 858, which exploded over the ocean, killing 115 passengers and crew. The killings were intended to influence the 1988 Summer Olympics which were to be held in Seoul, South Korea, later that year.

The C-4 threat is not only one faced overseas. Recently, an individual was convicted of possessing stolen C-4 explosives and threatening to use them against the Elkins (West Virginia) Federal Building. In 2014, the FBI arrested an individual in Texas threatening to blow up government buildings, rob banks, and kill law enforcement officers using C-4 explosives. And, in 2013, a U.S. Army soldier was arrested trying to sell C-4 explosives which he stole from Fort Hood, Texas.

Like any other weapon in the arsenal of those who would do us harm, C-4 and other plastic explosives can be deadly and deserve attention by homeland security officials. But, unlike the movies, controlling this threat is not quite as simple as cutting the red wire.

To learn more about C-4, its safety, and how it is used, see this HowStuffWorks article.


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