A mortar munition includes a mortar tube; first and second openings in the wall of the mortar tube, the first opening being closer to a breech end of the mortar tube than the second opening; a spring loaded valve assembly disposed in the first opening in the wall of the mortar tube; and a shoe assembly disposed in the second opening in the wall of the mortar tube. The spring loaded valve assembly is connected to a vacuum source. The vacuum source pulls the mortar bomb rearward in the tube. The shoe assembly includes a shoe that bears on the mortar bomb to hold it in place when the tube is in an elevated position.