Have to agree with Grimes and Viper on this.
Altitude and target aspect are the determining factor with these weapons.
From maximum range it is best to line your aircraft up for a head on/rear on attack, make sure to try and stay at least 2000m altitude when firing, this will give the vikhir longer to aquire the laser and stabilise in flight.
For shorter ranges altitude is still the key, the higher you are at launch the better they will track in to the target, and as Grimes mentioned keep the nose pointed at the target as much as possible and watch your airspeed to avoid closing to fast, the faster your closure rate the more erratic the missile path.