Oooohhh, the memories...
OK, get the picture. Dad takes 12-year-old son out to the range to start him in on the mysteries and rituals of milsurp rifle shooting. Weapon of choice is a WW2 Lee-Enfield in .303.
Dad illustrates to son how to load, aim and fire. Son follows suit. All goes well for a magazine full.
Dad asks son to reload under his supervision. Son does so, very pleased with himself (and full of it, as usual), then, without waiting for the command, chambers a round - not putting safety on, of course, as HE isn't going to make a mistake (that sort of thing only happens to others, doesn't it?).
Dad remonstrates (LOUDLY!) with son about not chambering round until muzzle is pointed safely down-range. Son duly points rifle down-range, resting butt against groin, with right hand around wrist of stock, and (you've guessed it) finger negligently resting against trigger. Son proceeds to give back-talk to Dad, something about "Lighten up", or some such thing.
Dad explodes (LOUDLY!) in son's right ear about the importance of safety and of LISTENING!!! Son jumps in response to sudden roaring in ear, and finger tightens on side of trigger.
Son's next memory is of lying in a foetal position, moaning, with certain vital parts of his anatomy feeling as if they've been through the wringer. Dad, after checking for signs of life, adds insult to injury by laughing inordinately, and telling others at the range that things like this are what make having a smart-ass, won't-listen son worthwhile at times. Son is further humiliated by hearing all present at the range join in the merriment.
On drive home, son has to lie on back seat, because he's not exactly fit to sit down on anything. On arrival home, son has to endure the sight (and sounds) mother and two sisters in fits of hysterical laughter.
And yes, since that day, son has NOT held loaded rifle in proximity to family jewels at any time!