I OC with my 10-year-old all the time. He's finally starting to remember to not hug that hip all the time (a few knocks in the noggin by the grip seems to have fixed that habit ) He hardly notices anymore.
Firearms are no secret, mystical thing in our house, either. I think it's easier to teach him everything he wants to know instead. He likes plinking with the pellet guns, and the 22 rifle (the 22 handgun, not so much - he's a little recoil shy still). He knows that if he ever wants to handle one, all he has to do is ask.