It's not that they won't approve I believe they would like the guy if they got to know him I just don't know if my grandpa will even give it a chance they are fairly strict
Why don't they know him?
Hasn't he been to your house to pick you up for a date? Haven't you introduced him to your grandparents?
Strict or not, your grandparents should at least be given the opportunity to meet and get to know anyone you have an interest in. While it is true that they may not like the guy and they could even forbid you from seeing him, their reasons for not liking him could be valid and worth your hearing. It is
also possible that whatever it is that has charmed you about him will charm them, too.
I personally don't like the idea of you seeing him without your grandparents knowing, though. That I believe can be a big (and potentially dangerous) mistake.
Good luck with whatever it is you decide to do.