Abstract: A composite gun barrel 10 with active cooling having a breech end and a dharge end. The barrel includes an outer jacket 11 having radially inwardly projecting ports 15 proximate the breech end 25 extending inwardly from the outer diameter of the jacket, and an inner liner 13 inside the jacket and extending beyond the discharge end of the jacket prestressed by autofrettage to form a permanent integral assembly. The inner liner has a circumferentially located annular space 17, the ports being in operable communication with the annular space. A plurality of circumferentially spaced longitudinal channels 19 on the liner extend from the annular space to a location 21 beyond the discharge end of the jacket. The liner includes a shoulder 23 located between the breech end of the barrel and the inwardly projecting ports for locating the jacket on the liner.