Abstract: An explosive cartridge for use in an explosive column train by end to end coupling of a plurality of cartridges. Each cartridge comprises a cylindrical containing shell having an open rear end in which is a closure plug. In the pre-mix condition, the cartridge contains a first solid component of a two part explosive. In field use the closure plug is removed and a liquid second explosive component is poured into the cartridge and the plug reinserted to form a sliding watertight seal with the cartridge. When several of the cartridges are joined in end to end relationship to form the explosive train, the nose end of one cartridge moves the plug of the adjacent forward cartridge inwardly to take up the slump in the explosive composition and maintain the closure plug seal.