A deployable fairing is driven off of high-pressure gun gases to reduce aerodynamic drag and extend the range of the artillery shell. An artillery shell is provided with a fabric fairing and a piston attached thereto in a rear section of the shell in a stowed state and a chamber. During launch high-pressure gun gasses are captured and stored in the chamber. Once the shell clears the end of the artillery tube, the pressure aft of the shell drops from the high pressure inside the tube to atmospheric pressure outside the tube. The high pressure gun gasses stored in the chamber act over the top surface of the piston to drive the piston aft against the much lower pressure behind the projectile to deploy the fabric fairing attached thereto to reduce the base area of the projectile creating or extending the boat-tail of the shell, hence reduce aerodynamic drag. The aft driven piston engages a locking mechanism that locks the piston in a deployed position.