Abstract: A self-contained, mobile refractory apparatus for repairing interior refractory walls of high temperature industrial ovens and furnaces by spraying fluent refractory slurry mixes to seal cracked and spalled areas thereof. The apparatus is mounted on a vehicle, and includes a base, a rotatable, articulated support mounted on the base, a pivotal gunning lance support secured to the articulated support, an elongated gunning lance mounted on the gunning lance support with capacity for selected reciprocal axial movement, a slurry pipe mounted rotatably within the lance and a spray nozzle affixed to the slurry pipe for spraying slurry. Reversible hydraulic motors impart selected reciprocal movement to the lance and selected rotary movement to the slurry pipe and its nozzle. The lance is constituted by a pair of elongated, concentric tubes having elongated supporting ribs interposed therebetween, to provide high strength and rigidity with minimum deflection in use.