These bombs belong to a class known as EFP –‘Explosively Formed Projectile’ or ‘Explosively Formed Penetrator,’ depending on who you’re talking to. They compress a metal liner into a slug and fire it at the target some distance away.
The picture shows what a real EFP munition looks like. This is the M2 Selectable Lightweight Attack Munition (SLAM). It’s small enough to put in your pocket and weighs a couple of pounds.
This version has been used by US Special Forces for the last 15 years or so. As GlobalSecurity.org describes it, SLAM is versatile, too:
The M2 selectable lightweight attack munition (SLAM) is a multipurpose munition with an anti-tamper feature. The SLAM is compact and weighs only 1 kilogram, so it is easily portable. The SLAM is intended for use against APCs, parked aircraft, wheeled or tracked vehicles, stationary targets (such as electrical transformers), small fuel-storage tanks (less than 10,000-gallon), and ammunition storage facilities. The explosive formed projectile (EFP) warhead can penetrate 40 millimeters of homogeneous steel.
The SLAM has two models — one is self-neutralizing (M2) and the other is self-destructing (M4): The M2 is solid green and has no labels, brands, or other distinguishing marks. This device is used by SOF and is not available to other units.
The M4 is green with a black warhead (EFP) face. This device is normally used by units designated as light, airborne, air assault, crisis response, and rapid deployment.
The SLAM has four possible modes of detonation–bottom attack, side attack, timed demolition, and command detonation. Bottom Attack: The SLAM has a built-in magnetic sensor, so it can be used as a magnetic- influenced munition against trucks and light armored vehicles. It can be concealed along trails and roads where target vehicles operate and can be camouflaged with dry leaves, grass, and so forth without affecting EFP performance. Mud, gravel, water, and other debris that fill the EFP cup have minimal impact on EFP formation and effectiveness as long as the debris does not extend beyond the depth of the EFP cup. The magnetic sensor is designed to trigger detonation when it senses a vehicle’s overpass. For the EFP to form properly, it needs a minimum of 13 centimeters from the point of emplacement to the target.
The bottom-attack mode is active when the selector switch is set to 4, 10, or 24 HOURS and the passive infrared sensor (PIRS) cover is in place. The SLAM will self-destruct (M4) or self-neutralize (M2) if the selected time expires before the SLAM is detonated by a vehicle.
Side Attack: The SLAM is equipped with a PIRS that was specifically developed for the side-attack mode. The PIRS detects trucks and light armored vehicles by sensing the change in background temperature when vehicles cross in front of the PIRS port. The PIRS is directional and aligned with the EFP when the device is aimed. The side-attack mode is active when the SLAM selector switch is set to 4, 10, or 24 HOURS and the PIRS cover is removed to expose the PIRS. The SLAM will self-destruct (M4) or self-neutralize (M2) if the selected time expires before it is detonated by a vehicle.
Timed Demolition: The SLAM’s built-in timer will trigger detonation at the end of a selected time. The timed-demolition mode is active when the SLAM selector switch is set to 15, 30, 45, or 60 MINUTES. In this mode, the magnetic sensor and the PIRS are inoperable, and the SLAM will detonate after the selected time has expired.
Command Detonation: This mode provides manual warhead initiation using standard military blasting caps and a priming adapter (Figure 4-7). The command-detonation capability bypasses the SLAM’s fuse and safing and arming (S&A) assembly. The SLAM has an anti-tamper feature that is only active in the bottom- and side-attack modes. The SLAM will detonate when an attempt is made to change the selector switch’s position after arming.
No doubt the Russians and Chinese have their own versions of SLAM, and these have probably been copied too. So you might expect a rougher, cheaper copy to appear in Iraq if it was supplied from the outside.
But as has been observed here, anyone can make crude and simple EFP munitions in a basic workshop. All you need is a lump of plastic explosive and a piece of copper. Shape the copper into a saucer, put the explosive under it, and you’re there. Obviously this will be a lot less efficient, accurate and reliable than something like SLAM (optimal design of the the metal ‘lens’ is an art requiring a lot of computer power), but you can compensate by making it ten times bigger if you need to.
Maybe the insurgents should be given some credit for being able to build their own gear, or maybe there’s more intelligence we don’t know. But if EFP mines were being supplied by an outside source, you might expect to see something a lot slicker.