The device has a ring with diameter same as that of a grenade. A propulsive shell (22) has gun powder (64) and a cup (66) at its one end situated on a side of a blasting cap. The shell has the ring fixed at the other end. The powder is housed in the cup inserted in an orifice traversing a shell's partition (50). The cup has a low resistance zone at its bottom to break the bottom under the pressure of combustion gas of the powder.