I know that the 3.7 AA projectiles have time fuzes and explode at a given height but how does 40mm Bofors fuzes work, seems to be no clock work mechanism for them. Were impact fuzes used? If so, you would have to be a bloody good shot to hit an aircraft high up. What happens to the ones that miss, quite a large round to have a self destruct fuze and it explodes hitting the ground.