A cartridge case having a plastic body has a metallic tubular mouth member affixed thereto. A generally cylindrical projectilereceiving portion may be crimped to securely hold a projectile and a rear portion of the mouth member is tapered to match the inner contour of the plastic case. Interaction of a circumferential rib with a forward gum chamber wall and the interaction of matching shoulders on the mouth member and the plastic body prevent separation of the mouth member from the cartridge case during firing, extraction and ejection. The mouth member provides enhanced reloadability for the cartridge case and produces a center of gravity matching that of metallic cartridge cases for optimum ejection characteristics.