While holding the lead weight in place with one finger (to prevent the linen tape from unwinding prematurely) the grenade was then thrown at the target.

When the Gammon grenade was thrown, the weighted linen tape automatically unwrapped in flight, pulling out a retaining pin from the fuze mechanism.

Removal of the retaining pin freed a heavy ball-bearing and striker inside the fuze, which was then held back from the percussion cap only by a weak creep spring.

Impact with the target gave the heavy ball-bearing a sharp jolt - overcoming the weak resistance of the creep spring - that slammed the striker against the percussion cap.

The percussion cap fired directly into the adjacent detonator, which in turn sent a violent shockwave into the main explosive filling contained inside the stockinette bag.