A method and device for cooling a gun barrel wherein coolant is provided to the gun barrel via a nozzle arranged at the downstream end of a pressure feed line arrangement. The coolant is originally conveyed from a reservoir into a pressure cylinder, while the pressure feed line between the pressure cylinder and the nozzle is closed. Thereafter, the coolant in the pressure cylinder is placed under a predefined operating pressure. Prior to firing a round, the pressure feed line is opened, so that the coolant flows to the gun barrel before firing. When firing a shot, the coolant in the gun barrel is compressed to a pressure above the predetermined operating pressure by the firing gases and pushed out of the gun barrel. In the process, the coolant is expanded into a buffer reservoir adjacent to the nozzle and is injected back into the gun barrel after the gas pressure built up has been reduced to the predetermined operating pressure.