Clarifying EFPs and Shaped Charges

In response to yesterday's query, we got several helpful clarifications. Below I've quoted an excellent breakdown of the differences by David Hambling (author of Weapons Grade...) Thanks also to Joshua Foust at Registan.

The bottom line is that EFPs are a specific type of shaped charge that is new to Afghanistan; they have less penetrating capability but with much greater range, which makes them very difficult to defend against. It's one thing to protect against a mine that only blows up when you go over it, and another thing entirely when that weapon can be concealed alongside the road. They newly introduced mines are not difficult to make once you know the specifications.

While in the same general class, EFPs are distinct from normal shaped charges. MORE

Photo: An EFP in Iraq.

A standard shaped charge is  hollow cone lined with metal (usually copper); then the explosive detonates, the metal is formed into a very narrow jet moving at several thpusand metres per second. This has excellent armor-piercing properties, usually quoted as being up to six times the diameter of the charge, but a very limited range (the jet loses focus after a metre or so).
 
By contrast, an EFP is a very shallow cone lined with metal. Detonation produces a single aerodynamic slug which is relatively slow and has much less penetration ability (approximately the same as the charge diameter), but the slug has an effective range of tens of metres or more. This makes it very dangerous as an 'off route' mine which can be placed beside a road.
 
The recent EFP find in Kabul appears to mark the introduction of a new weapon into Afghanistan.
 
My personal view is that while EFP technology may or may not be coming from Iran, you certainly don't need advanced technology to make them. Once you have a workable 'recipe' and know the size, exact shape and grade of metal needed, it can be copied by anyone with workshop facilities.