A piston/rocket projectile for use within a launcher system having a barrel and method of firing such are presented herein. The projectile comprises a projectile body having a combustion chamber for propellant, a piston moveable to extend out a base of the projectile as a result of ignition of propellant in the combustion chamber, and vents for expulsion of combustion products from the ignition of propellant out of the projectile base after initial movement of the piston. A casing is secured to the base of the projectile body, enclosing the piston and vents prior to the ignition of propellant, and a separable joint is disposed between the casing and the base of the projectile body. Upon ignition of propellant in the combustion chamber, the projectile piston is forced down and the separable joint is caused to separate, leaving the casing in the barrel. After the piston completes exertion of propulsion force, combustion products of the ignition of propellant are expelled through the vents out of a lower end of the projectile and solid combustion byproducts from the ignition of the propellant are collected in the casing.