30.06 when I was about 6-7 years old.
First time I recall shooting a full sized rifle. My father had a rough way of teaching the important lessons.
Standing, full size rifle. Only instructions were "point it that way". Could barely hold it straight out. Didn't know to put it right against shoulder of course. Pulled the trigger and knocked me on my ass.
Shoulder hurting, upset, pulls me up on my feet. Says, "now you know not to screw around with guns kid, these things are not toys".
He then proceeded to give proper instructions that still lasts to this day in one form or another. The more experienced I get the more I realize his depth of knowledge and experience with firearms far exceeds the norm. Far exceeds..... Of course I saw all that as a child esp. when being drug around all over the place shooting, hanging out in old cats gun shops, watching guys with lathes doing the most amazing things to build guns (amazing to a 6 yr. old for sure), I did more reloading with him by 10 yrs old than most do in a lifetime, was casting my own bullets before I was 8, so on and so on ...
Anyway, we get home from that first 30.06 round, my shoulder was throbbing and bruised, Mom was freaking out at my Dad asking what the hell he did to me .... "well, now he knows this stuff isn't to be messed with".
Can't imagine teaching my little guy in that manner but I tell you, I LEARNED the lesson. 30.06 isn't that big a deal now of course but back then, I swear I was hit with a cannon.