The invention relates to needleless syringe for injecting an active liquid principle. The inventive syringe comprises a container (3) closed by a movable shutter and containing the injectable liquid. Said container is initially insulated from an injector-receptacle provided with a cylinder bore (10) in which a downstream shutter is arranged and which comprises at least one protuberance reducing the section with respect to the upstream opening of the bore. The aim of said invention is to damp and prevent the downstream shutter bounce when it is disposed in the bore (10) of the receptacle.