Abstract: A projectile, such as a guided mortar projectile, has both a front obturator and an aft obturating device. The aft obturating device is located aft of the front obturator, and serves to trap pressurized gases behind the aft obturating device, so as to provide further propulsion to the projectile with the trapped pressurized gases, even after the front obturator has cleared the muzzle of a launcher. The aft obturating device provides less resistance to movement of pressurized gases across the aft obturating device in the aft direction, than to movement of pressurized gases across the aft obturating device in the forward direction, and may act as a check valve with regard to such gas flows. The aft obturating device may be part of a cap that is coupled to a tail boom of the projectile, and that drops away from the projectile after launch.