I was tempted to go through here and tear into those saying that someone 18 years of age isn't mature enough to carry a handgun but I see that's being done already.
Don't hold back on my account. Part of the confusion here is that I don't think anyone is specifically saying that "no 18-yr-old is mature enough," but rather that the totality of experience suggests that few of them are. The business about the military is a canard, because it isn't an apples-to-apples comparison. Young people can enlist precisely because they are immature and can be molded, they have less self-preservation instinct, and they are easy to recruit.
Actuarial statistics don't lie - automotive insurers
have the data:
The risk of being involved in a car accident is highest for drivers aged 16 to 19 than it is for any other age group. For each mile driven, teen drivers ages 16 to 19 are about four times more likely than other drivers to crash.
So. Does that mean that you, personally, were a poor driver in your teens? No, it doesn't. It means that teen drivers are 400-percent more likely to be poor drivers. Since we know from developmental science that an 18-year-old has adequate reflexes to operate a car, their high rates of accidents stem from their lack of experience and poor judgement.
We also know that teens are far, far more likely to crash as a result of having teen passengers in the car. The addition of each additional passenger increases the risk. This is so well documented that some states restrict provisional drivers to not having non-adult passengers at all.
And this gets us around to part of the issue: The young CCW owner may have problems when peers are asking to see the gun, daring the owner to draw it, urging him to use it, etc. The teen environment tends to involve social situations like parties, drug use, dating, contests of skill, etc. Thus on the whole, restrictions about ownership and CCW age are a kind of compromise, as they are with alcohol and tobacco, such that we've chosen a cut-off line that recognizes these realities.
Indeed, to the advocate who stoutly maintains that there should be no firearm restrictions for high schoolers, one would ask where that line should be drawn, if at all? To the real purist on this issue, the answer is "zero limits of any kind for anybody, anywhere, at any time." If the parents are fine with it, then 5 or 6 should be A-OK, right? Or maybe 10? If you have a line you won't cross, where are you drawing it, and why?