One thing you might try... and Menthorn would look at... If the ram gets stuck somewhere along the way then it might not make it to the venting holes. So as a test fix the ram in such a position and put the pressure on. If it blows it blows otherwise.. a clean bill of health id say. As for exuasting the high pressure CO2.. make sure to use a falve vent (i.e. 3/2 valve). Just incase the piston doesnt reach the venting position.