Explosively formed penetrator An explosively formed penetrator ( EFP ) , also known as an explosively formed projectile , a self - forging warhead , or a self - forging fragment , is a special type of shaped charge designed to penetrate armour effectively at standoff distance s . As the name suggests , the effect of the explosive charge is to deform a metal plate into a slug or rod shape and accelerate it toward a target . They were first developed during WWII . Difference from conventional shaped charges . A conventional shaped charge generally has a conical metal liner that projects a hypervelocity jet of metal able to penetrate to great depths into steel armour ; in travel over some distance the jet breaks up along its length into particles that drift out of alignment , greatly diminishing its effectiveness at a distance . An EFP , on the other hand , has a liner face in the shape of a shallow dish . The force of the blast molds the liner into any of a number of shapes , depending on the shape of the plate and how the explosive is detonated . Some sophisticated EFP warheads have multiple detonators that can be fired in different arrangements causing different types of waveform in the explosive , resulting in either a long - rod penetrator , an aerodynamic slug projectile , or multiple high - velocity fragments . A less sophisticated approach for changing the formation of an EFP is the use of wire - mesh in front of the liner : with the mesh in place the liner fragments into multiple penetrators . In addition to single - penetrator EFPs ( also called single EFPs or SEFPs ) , there are EFP warheads whose liners are designed to produce more than one penetrator ; these are known as multiple EFPs , or MEFPs . The liner of an MEFP generally comprises a number of dimples that intersect each other at sharp angles . Upon detonation the liner fragments along these intersections to form up to dozens of small , generally spheroidal projectiles , producing an effect similar to that of a shotgun . The pattern of impacts on target can be finely controlled based on the design of the liner and the manner in which the explosive charge is detonated . A nuclear - driven MEFP was apparently proposed by a member of the JASON group in 1966 for terminal ballistic missile defense . A related device was the proposed nuclear pulse propulsion unit for Project Orion . The ( single ) EFP generally remains intact and is therefore able to penetrate armour at a long range , delivering a wide spray of fragments of liner material and vehicle armour backspall into the vehicle ' s interior , injuring its crew and damaging other systems . As a rule of thumb , an EFP can perforate a thickness of armour steel equal to half the diameter of its charge for a copper or iron liner , and armour steel equal to the diameter of its charge for a tantalum liner , whereas a typical shaped charge will go through six or more diameters . The penetration is proportional to the density of the liner metal ; tantalum 16 . 654 g / cm , copper 8 . 960 g / cm , iron 7 . 874 g / cm . Tantalum is preferable in delivery systems that have limitations in size , like the SADARM , which is delivered by a howitzer . For other weapon systems where the size does not matter , a copper liner of double the calibre is used . Extensive research is going on in the zone between jetting charges and EFPs , which combines the advantages of both types , resulting in very long stretched - rod EFPs for short - to - medium distances ( because of the lack of aerostability ) with improved penetration capability . EFPs have been adopted as warheads in a number of weapon systems , including the CBU - 97 and BLU - 108 air bombs ( with the Skeet submunition ) , the M303 Special Operations Forces demolition kit , the M2 / M4 Selectable Lightweight Attack Munition ( SLAM ) , the SADARM submunition , the Low Cost Autonomous Attack System , and the TOW - 2B anti - tank missile . An EFP eight inches in diameter threw a seven - pound copper slug at Mach 6 , or 2 , 000 meters per second . ( A . 50 - caliber bullet , among the most devastating projectiles on the battlefield , weighs less than two ounces and has a muzzle velocity of 900 meters per second . ) — Rick Atkinson , " The Washington Post " Use in improvised explosive devices . EFPs have been used in improvised explosive device s against armoured car s , for example in the 1989 assassination of the German banker Alfred Herrhausen ( attributed to the Red Army Faction ) , and by Hezbollah in the 1990s . A recent development is their widespread introduction in IED s by insurgents in Iraq , to penetrate the Armor of M1114 and M1 Abrams . The charges are generally cylindrical , fabricated from commonly available metal pipe , with the forward end closed by a concave copper or steel disk - shaped liner to create a shaped charge . Explosive is loaded behind the metal liner to fill the pipe . Upon detonation , the explosive projects the liner to form a projectile . Effects of traditional explosions like blast - forces and metal fragments seldom disable armored vehicles , but the explosively formed solid copper penetrator is quite lethal — even to the new generation of mine - resistant vehicles ( which are made to withstand an anti - tank mine ) , and many tanks . Often mounted on crash barriers at window level , they are placed along roadsides at choke points where vehicles must slow down , such as intersections and junctions . This gives the operator time to judge the moment to fire , when the vehicle is moving more slowly . Detonation is controlled by cable , radio control , TV or IR remote controls , or remote arming with a passive infrared sensor , or via a pair of ordinary cell phones . EFPs can be deployed singly , in pairs , or in arrays , depending on the tactical situation . Simplified improvised multiple explosively formed penetrators ( SIM - EFP ) . At close standoff distance there is no need for the cone - tailed projectiles ' aerodynamic stability , which means that the liner can be simplified . The SIM - EFP is a construction that fits in between the military linear cutting charge ( see shaped charge ) and the platter charge ( see improvised explosive device ) . The main difference is how much the rectangular liner plate is bent . SIM - EFPs are built from simple cut and bent steel bars , side by side , with explosives attached . Upon explosion it creates multiple projectiles spread out along the vehicles ' length , which makes it more probable that the enemy troops inside the vehicle are hit . The construction also allows for longer timing errors , and makes it easier to hit fast moving vehicles . The SIM - EFP is a modified version of the platter charge , but the projectiles are better optimized for armour penetration instead of demolition , and spread out perfectly for effective killing of armoured vehicles ( optimized for long projectiles instead of a broad flat projectile ) . The simplified EFP design also makes it easier for small groups of motivated individuals to build big EFPs that can penetrate a heavy battle tank or stationary high - value targets of virtually any sort . Other examples of non - circular EFPs are U . S . patents 6606951 and 4649828 . Other terrorist uses In Northern Ireland similar devices have been discovered that were developed by dissident Republican groups for intended use against the police . Use in Hayabusa 2 . The spacecraft Hayabusa 2 will carry a Small Carry - on Impactor ( SCI ) . It will be dropped off Hayabusa 2 on to an asteroid and detonated . The explosion will form a copper explosively formed penetrator hitting the asteroid with a velocity of 2 km / s . The crater created by the impact will be a target for further observations by the onboard instruments . The shaped charge will consist of 4 . 5 kg of plasticized HMX and a 2 . 5 kg copper liner .