I know that you don't want to hear a back in the old days story but here it comes..lol. At Christmas, age 7, I got my first 22 and a 50 count box of shells from my grandparents. It was an Ithaca mod 49 single shot. I was told " Don't shoot any songbirds, Grandmas chickens or Granddads cows, now go outside and play"
I started my kids out on the same Ithaca 49 at age 7, but only when I was with them.
I started my grandson out at age 6 with a BB gun. He is now 7 and when we go to the range he shoots the Ithaca 49.
You can see that in in my family, over the last five generations of hunters and fishermen, the magic number is seven years of age.