There are several constiutional rights with imposed limits. Just like those under 18 cannot vote, I think those under 21 should have to have a guardian if they want to go shooting. I don't think an 18 year old should be able to go out and buy a gun without a parent. You do. I think we've reached the end of usefullness of this debate.
FYI, I am not an anti gun type. My dad started taking me shooting when I was eight.
PD