Double edged sword. The irresponsibility of young drivers is well known. So how does that help the gun argument? Maybe we should take away their cars? It's been argued.
Actually, a ten-year-old can buy a car if they want. I don't know who would sell it to them, but there are no laws that I know of that forbid it. Now, getting a license isn't usually allowed until age 16, but then again, cars (and driving) do not enjoy specific constitutional protections. Arms do.
Also, one can argue that rifles and shotguns are more important in a sporting paradigm. That is not a major reason for handguns (yes, folks do handgun hunt).
Here's the thing. Heller
mainly covered the right to own a handgun
for the purposes of self-defense
. It can be read (as the 7th Circuit did in Skoien
) that such is the central right protected by the 2nd Amendment, and that "hunting" and "sporting" are not as sternly protected.
As such, we're back to the question of a unique and arbitrary restriction on what is considered a fundamental right: owning a handgun.