i looked through some pictures of the sights cva has and it sounds like you have the plastic sights.
The front sight uses an insert that has the fiber optic attached to it. Simply remove that and inside there will be the screw to remove the base of the sight from the barrel.
If you go back to using open sights i highly recommend that you ditch the plastic sights and buy the Durabright sights for $18. They are aluminum or steel, forget what they are made out of.