Abstract: Cartridge cases of the type which receive powder, a wadding and shot pellets are comprised of thermoplastic material and have a metal head. The head is joined to the plastic case body in an operation wherein heat and pressure are applied to cause the plastic material to flow both outwardly into the interior of a rim portion of the metal head and also inwardly into an annular recess defined in part by an internal reinforcing section of the case body. The reinforcing section of the case body may be either integral with or separable from the remainder of the cylindrically shaped case and the cylindrical portion of the case is provided with an extension which is deformed, by the application of heat and pressure during the manufacturing process, to form the element which locks the head to the plastic body.