Abstract: A notched cartridge or casing is provided to mitigate the shock damage to a gun barrel or firing chamber when a cartridge with large amounts of explosive or propellant is fired. The cartridge or casing comprising a generally cylindrical shell with an open top end and a closed base is provided with an annular area near the base and a circular area on the base which have reduced wall thicknesses compared to the rest of the cartridge. The annular and circular areas have external surfaces which are inwardly displaced with respect to the outer surface of the remainder of the cartridge. Upon firing of the cartridge, the areas of reduced wall thickness expand outwardly and are plastically deformed without touching the barrel or firing chamber. Damage to the barrel and/or breech is prevented and the cartridge is easily removed for reloading of the gun system.