Keep in mind you are shooting an arrow that is a LOT shorter then your old arrow. This means the broadhead can take control much easier. Also with half moon nocks, you need to make sure the moon is at a 90 with the odd fletch. If they are in at different angles, they can fly differntly. Like DNK mentioned, make sure you are cocking the bow well. Also make sure you stay in the shot until the arow hits. The more you site in, the more you want to pull your head out to see where the arrow hit.
Make sure your front end bolt is tight as well.
Randy