I....W-wha......Excus.....The targeting reticule for low velocity rounds has to take into account the relative motion of both ships. If you're flying backwards and your enemy is flying away from you, your cannon shots will never hit. The reticule knows this and won't display any targeting lock for shots it knows it will miss. I had to get used to this when I tried medium cannons on something as manoeuvrable as the Viper. You have to be careful what way you're drifting and at what speed if you expect your guns to be able to aim properly. I also find it necessary to switch gunsight mode from leading to trailing if the projectile weapons are mounted on the underside of the ship.