Abstract: In a weapon subject to a sequence of high acceleration followed by high spin and including a detonator and an explosive charge; the improvement comprising a barrier having two parts located between the detonator and explosive charge to normally form an obstruction to prevent accidental detonation of the explosive charge by the detonator. Mechanical locking means are provided to lock the barrier in place, comprising a split cylinder and a spirally wound ribbon, a pair of pins restraining the outer surface of the ribbon to prevent premature unwinding. When the weapon is fired from a gun, the high acceleration will remove the pins and allow the ribbon to unwind. Upon unwinding the entire ribbon, the barrier under the action of spin, will be removed to provide an unobstructed path between the detonator and explosive charge.