Abstract: A ram-borer apparatus is described which comprises a tubular housing, a percussion piston which is movable axially to and fro in the housing, and a striker-tip which is arranged to slide in an axial direction relative to the housing and which bears against the housing in the working direction via a resilient member. In accordance with the invention, there is attached to the rear end of the housing a drag-sock for coupling a tube or cable, etc. to the housing, and/or an expander-cone for enlarging the bore formed by the apparatus, and/or a steering tube for steering the apparatus along a straight or preselected arcuate path.