Let me preface my post with this... I AM NOT A LAWYER!!
Hmm... I don't know the legalities of ownership for an 18 year old but OC ins't illegal for someone your age. This leaves me to believe that if you are legally OCing then ownership of the gun isn't the business of the police department. What I mean is if you aren't breaking the law then they have no right to stop, question or detain you. Now, finding a way to make that work in your favor is another thing entirely.
Good luck to you. Hopefully somone with more experience in this matter will chime in and give you better direction.