Abstract: A trigger assembly for launching the projectile of a spring loaded weapon such as a harpoon, cross-bow or the like is disclosed having a detent adapted to engage the rear end of the projectile. The detent swingable about an axle fixed to the butt stock and a spring member is supported within the butt stock to engage said detent. The forces created by the projectile acting on the detent, cause said spring member to curve into a reactive position, the curvature of the spring in the reactive position is limited and a trigger member is provided for displacing the spring from its curved position into a position releasing the reactive force on said detent.