8. AN AIR PRESSURE OPERATED ARMING DEVICE COMPRISING A HOUSING; A CHAMBER FORMING PART OF SAID HOUSING INCLUDING A SNAP-ACTING DIAPHRAGM OVERLYING SAID CHAMBER, A FIRING PIN ATTACHED TO SAID DIAPHRAGM AND MOVABLE THEREWITH; SEALING MEANS INCLUDING A RESILIENT MEMBER PROVIDING A GAS-TIGHT SEAL BETWEEN SAID HOUSING AND SAID DIAPHRAGM ADJACENT SAID FIRING PIN; A PRIMER CARRIAGE INCLUDING A PORT AND A PRIMER CHARGE IN SAID PORT ARRANGED FOR MOVEMENT RELATIVE TO SAID FIRING PIN SUCH THAT WHEN SAID CARRIAGE IS IN A FIRST POSITION SAID PORT IS OUT OF ALIGNMENT WITH SAID FIRING PIN AND WHEN SAID CARRIAGE IS IN A SECOND POSITION, SAID PORT IS IN ALIGNMENT WITH SAID FIRING PIN, AND LEVER MEANS MOVABLE IN RESPONSE TO MOVEMENT OF SAID FIRING PIN FOR MOVING SAID CARRIAGE FROM SAID FIRST POSITION TO SAID SECOND POSITION.