Gunnut17, most (if not all) of the rights in the BoR have been limited in their application, and always have been. For example, 4-year-olds do not have a right to vote, and (AFAIK), never have had. Why? For one, because they cannot utilize that right in any meaningful way. I would also say that the RKBA has a similar logical limit as to the earliest point at which a person can exercise the right. Is 18 the right point? Certainly, there are 17-year-olds who could be trusted with a gun. 14-year-olds? Yeah, probably a few. The question becomes, then, "Where do we draw the line?"
I'm a lawyer, but I'm not your lawyer. If you need some honest-to-goodness legal advice, go buy some.