Federal law prohibits handgun sales under 21. But states allow possession of these handguns to folks 18 and over. Makes no sense. Should be 21 for all firearms, period. The problem is, of course, with those who serve in the military. They'll be like "wait, I can fire guns at people you want me to kill in Iraq, but you don't trust me to own a weapon here at home??"
I get their point. I don't know what solution there is there, except to offer an exception to those with active military service.
But kids these days are just too immature to own firearms. I see it all the time at the range.
Troops would of course be granted an exception which would continue it they completed their tour or were honorably discharged. We already do it with alcohol.