mulestar,
just my own personal experience... but..... i started shooting a 22lr when i was a kid, plinked around with that until my dad put me behind a 16g remington 1100 auto, i thought it was gonna kick like an SOB for my 12yr old frame, I fired a couple shots but it wasn't as bad as I thought it would be, by the time I was 15 I was shouldering the 7mag (I only weighed about 95-100 lbs at that age, i was short and skinny), it certainly kicked a lot harder but it wasn't so bad that i was afraid of it and I've never developed a flinch... since then I've put down probably about 50,000 rounds of 5.56 nato and 7.62 nato while i was in the infantry, of course those things kicked like a bb gun and I developed a good technique, still shootin my 7mag and love it, maybe some day I'll get a big dog gun like a .375 or even a .338... I think it depends on the shooter whether or not you develop a flinch... my 7yr old was shocked at the kick of the 243 and he thought the 20g was nasty, but he only weighs 55lbs so of course its gonna put a whoopin on him... btw - he's goin to the tree stand this year around christmas for his first whitetail... can't wait to get pics of it...