The present disclosure relates to a needleless injector including a cap, an injection system, a body, a gas generator, and a percussion device. The body is covered by the cap and is mounted to slide relative to the cap. The percussion device includes a striker that is slidingly mounted along a sliding axis between a rest position and a percussion position and a lock mechanism. The lock mechanism includes a lug and a retention tab. The lug projects from a peripheral face of the striker along an axis that is perpendicular to the sliding axis and has a first support ramp. The retention tab is attached to the cap, and has a second support ramp. The ramps are configured to move the retention tab radially when pushed by the striker from a retaining position to a release position and the retention tab is moved aside to release the striker.
