You can either lower the front sight or raise the rear (remember, adjust the rear sight in the direction you want the point of impact to move, and the front sight in the oposite direction). You might want to go to Brownell's site and they have a sight calculator you can use to determine what height front sight you need.
If the previous owner had a receiver (peep) sight on the rifle, he may very well have installed a higher front sight. If there is a gunsmith near you, you might talk to him about it and see if he will put a lower front sight on the rifle.
-WH-