You\'re fighting convergence, My good man.
What you have here is multiple cannons, all far away from the center of your craft/point of view, all trying to strike a single target. In order to do this, each individual cannon needs to aim inwards at the same spot, separate from the other cannons, and converge on a single point, the enemy target. The game handles this automatically, but Said enemy target is always moving. Closer and farther, left and right, up and down. based on what your cross hair is on when you pull the trigger, the computer adjusts all your separate weapons for that one point. but since your target keeps moving after this, your shots converge at the right point in space, but your target is no longer there, so your shots crisscross and shoot out into the distance. On top of this, you, the player, also have to lead your shots, trying to hit the target where you think it\'ll be by the time your shot makes it down range.
In short, you\'re trying to get several separate guns to hit a moving target from a single viewpoint.
Try this: Instead of several guns far apart, build one gun and either give it it\'s own cockpit viewpoint and aim from there, or mount said gun right under your main viewpoint. You\'ll have zero convergence issues, and will only have to worry about leading your target.
I have a 32 mass starfighter with a single twenty-block AMC in it\'s nose, right under My cockpit, and I have no trouble dropping AI targets, because I only need to lead My shots, and not have to worry about mis-convergence or alignment issues.
Hope this helps, and good hunting.