Abstract: A method for formation of slugs in a gun barrel and acceleration of these slugs up to the speed of 3 km/sec and more is suggested. A selected region of the barrel is filled by water or another liquid, mixture of liquids or slurry. The refrigerating media is supplied into a heat exchanger cooling the selected section of the barrel. The freezing conditions (rate of the heat removal, duration of cooling) assure desired cohesion of the slug and its adhesion to the barrel. When freezing is completed, the axial pressure is exerted on the internal edge of the slug. When the pressure exceeds the adhesion forces, the slug will move toward the open end with acceleration determined by the axial forces. If the exerted pressure force is not sufficient for the slug separation the expansion radial forces are applied to the barrel or the interface between the slug and the barrel is heated. After the separation the compressed media drives the slug toward the open end of the barrel.