Abstract: A ballistics fire control system for a spin or fin stabilised projectile is provided with means which are operated such that the closest point of approach between a fired projectile and a target is taken to be at the instant the projectile velocity vector (6) is orthogonal to the position error vector (13) between the projectile and target in accordance with the relationship: Vp·(PP−PF)=0 where Vp is the projectile velocity vector, PP is the projectile trajectory or position vector, PF is the target future position vector, · is the vector dot product and (PP−PF) is the position error vector.