Abstract: A self-propelled pnuematic burrowing device having an axially reciprocating percussion plunger arranged inside a tubular casing so as to strike a percussion head at the forward extremity of the casing, thereby advancing the device through the ground by crushing and/or displacing the material in the path of the device, the percussion head being freely displaceable between axial abutments defined by a guide sleeve of the casing, the displaceability being slightly in excess of the advance of the device per stroke and adjustable through the insertion and removal of split spacer rings. The air controls of the device, located in the rear portion of the casing, include a control barrel with an enlarged control head and a gradually widening central air supply channel.