A cartridge for reinforcing explosive priming, the cartridge comprising: - a removable lid and a receptacle, preferably made of plastics material, having a substantially cylindrical rigid tubular outer wall closed at one end by a transverse wall forming a floor and configured to be closed at its other end by said removable lid; and - an explosive material and preferably at least one detonator or detonating cord arranged within said receptacle; - said explosive material being in the form of at least one compressed solid block suitable for matching substantially the shape of an internal compartment (1d1) defined by said cylindrical outer wall of the receptacle and by said floor, said block of explosive material being of a shape defining within it at least one longitudinal cylindrical cavity open at one end (3b2) only so as to form a detonation housing suitable for receiving a said detonator or detonating cord; said lid including at least one detonator insertion orifice arranged facing the opening (3b2) of said detonation housing when said block of explosive material is inserted in said empty internal compartment (1d1) of the receptacle; the cartridge being characterized in that: - said detonator insertion orifice is closed in part by a cap comprising at least one deformable element (2a1) suitable for allowing a said detonator or detonating cord to be inserted by passing through said insertion orifice into said detonation housing and for preventing said detonator or detonating cord from exiting in the opposite direction through said insertion orifice once in place in said detonation housing; and - said floor includes at least one vent (1c1) suitable for discharging air and/or water through the floor when said block is inserted into said receptacle and when said cartridge is inserted into water, in particular water in a borehole filled with water. - a removable lid and a receptacle, preferably made of plastics material, having a substantially cylindrical rigid tubular outer wall closed at one end by a transverse wall forming a floor and configured to be closed at its other end by said removable lid; and - an explosive material and preferably at least one detonator or detonating cord arranged within said receptacle; - said explosive material being in the form of at least one compressed solid block suitable for matching substantially the shape of an internal compartment (1d1) defined by said cylindrical outer wall of the receptacle and by said floor, said block of explosive material being of a shape defining within it at least one longitudinal cylindrical cavity open at one end (3b2) only so as to form a detonation housing suitable for receiving a said detonator or detonating cord; - said detonator insertion orifice is closed in part by a cap comprising at least one deformable element (2a1) suitable for allowing a said detonator or detonating cord to be inserted by passing through said insertion orifice into said detonation housing and for preventing said detonator or detonating cord from exiting in the opposite direction through said insertion orifice once in place in said detonation housing; and - said floor includes at least one vent (1c1) suitable for discharging air and/or water through the floor when said block is inserted into said receptacle and when said cartridge is inserted into water, in particular water in a borehole filled with water.