I had my first gun when I was 14. Granted I was not allowed to "play" with it unsupervised. But I had been though the local Firearms saftey course and passed with flying colors. (went on to teach that course for 14 years btw)
By the time I was 18 I had shot deer, grouse, partridge, squirrel, and rabbit.
All brought home, cleaned by me, cooked by mom.
I don't know if todays generation has grown up with the same sense of what is taboo.
I had a pocketknife by the time I was 10. Everyone had one, everyone KNEW that to hurt someone with it was absolutely worse than death itself. We'd of never dreamed of pulling it on someone. I don't think that much of the current generation has the same sense of right & wrong.
I don't think you should say no one under 18 should be allowed to have a gun. Some over 35 shouldn't, and some under 16 should. Its a maturity and responsibility issue, not an age issue.