The inner liner over the propellant in a perforating charge, most often made of pressed, powdered copper mixture or drawn or stamped from copper sheet. The liner deforms as the charge is fired and its mass is added to that of the jet from the charge
George E. King Engineering, 5000 Oilfield Terms: A Glossary of Petroleum Engineering Terms, Abbreviations and Acronyms, US 2010. http://gekengineering.com/Downloads/Free_Downloads /Glossary_of_Petroleum_Engineering_Terms_25_August _2010.pdf, (Oil - Amer) {593}