My guns do not fire where I expect them to fire

The most common reason for this is that you have configured the guns to have a high error in muzzle velocity, orientation and/or elevation. Open the scenario you are using inside the VBS2 mission editor, and open the VBS2Fires Gun-line object that corresponds to the guns you are concerned about. Check their actual error values and ensure they are sensible. For muzzle velocity they should be 0.1 or less. For elevation and orientation they should be 0.3 or less.
If you are using grid coordinates, ensure that you are entering an eight figure grid reference and that you are using the correct coordinates system.
If you are using polar coordinates, ensure that you have provided an accurate update of the observer’s current position.
Because all rounds follow a ballistics trajectory, the effect of the ground and terrain contours may affect your fall of shot. This accurately reflects what happens in the real world, but may be the cause of the confusion here.