Abstract: A device capable of perforating strong walls, then of injecting a fluid through the same walls, is described. The device is intended essentially for intervention crews such as personnel assigned to maintain order or fire-fighters. The perforator-injector has a piston (1) which can be displaced in a cylinder (2,3) under the influence of a power fluid under high pressure. In order to increase the perforating power without inducing a too great initial recoil, the perforator-injector is equipped with a percussion mass (4) which is interposed between the head (1b) of the piston and a source of power fluid under high pressure. This mass is initially kept at a distance from the head of the piston and is capable of sliding in the cylinder (2,3).