Targeting in sights:

While you are in the Target Range and 
ready to shoot at the target, press 
ALT+CTL+T and the "Weapon Sighting
Information" will be on. Fire the weapon.
You should see the targeting coorinates 
(X-Y). Use the arrow keys tobring the 
weapons targeting coordinates to 
zero-zero (X=0, Y=0). Now the weapon is 
perfectly sighted.