69 grenade primers

Discussing with a friend about the mechanism of the 69 grenade fuze, it seems it would take a lot of force to strike of the primer to set of the detonator for this grenade if the primer was a normal type pistil primer. What type of primer was used in these grenades were they very sensitive. I noticed that some other type fuzes have sharp needle type firing pins like the Japanese Knee mortar fuze type 88. The 69 grenade firing pin is a two pronged pointed pin affair. Can anyone enlighten.

These shouldt be the sensitiv cap