Abstract: A pressurized fluid-powered actuator includes a housing and a striker movably coupled to the housing. Resilient sealing means are positioned between the striker and the housing. The sealing means are compressible so as to seal an end of the housing responsive to a force exerted on the sealing means by the striker in a first direction toward the housing. Releasable retaining means are operatively coupled to the striker and are structured to prevent motion of the striker in a second direction opposite the first direction prior to activation of the actuator, and responsive to a reaction force in the second direction exerted on the striker by the sealing means when the sealing means is compressed.