RE: age for starting to shoot
My grandfather got me my first BB gun at age 4, which I shot in his yard for many many hours. Around the same time we started to go hunting. At the end of every hunt (I didn't carry any gun, bb or otherwise) I would get to shoot the shells out of his Remington 22 Semi-auto. I was small enough that I had to put the stock on top of my sholder to be able to see through the scope.