A gunning apparatus for repairing a furnace lining is provided with a spray pipe of non-circular hollow cross-section. The spray pipe of non-circular cross section slidably moves back and forth within a rocking sleeve by a slide mechanism while the spray pipe is non-rotatable relative to the slide mechanism and is rotatable only by the rotation of the slide mechanism, whereby the shooting pipe is manipulated without weakening the rigidity or strength thereof which usually occurs on a conventional circular shooting pipe which requires keyways for rotation thereof.