The Rocket Launcher Mark 108 has a capacity of 22 rounds of the 12.75-in. Rocket Mark 1 Mod 0. Rapid firing of these rockets produces a considerable temperature rise in the launcher guide tube, and tests were conducted to determine whether the twenty-second round would cook-off if allowed to remain in the guide tube. Instrumented rounds were placed in an artifically heated guide tube and allowed to cool to ambient temperature, following as closely as possible the cooling rates prevailing in the service tube. Tests were conducted on rocket rounds incorporating various combinations of live and inert components. Tests were also conducted to determine the blast and heating effects upon rounds in the ready service ring of the Mark 108 launcher when the motor of a rocket in the guide tube is accidentally ignited with the tube in the vertical loading position. Various combinations of inert and live components were tested in a simulated mount.