When my dad was in basic training the Drill Sgt. put an M-14 up to his chin to prove that it didn't have much of a recoil. He had done it several times before but this time he broke his jaw. When I was in basic, our drill sergeant put the butt of an M-16 up to his crotch and fired off a few rounds to emphasize the light recoil. Fortunately, he didn't have the groin equivalent of a broken jaw.
All our range sgt. did was shoot through an ammo box with an m16. Not very impressive.