A friend and I found some old .303 rounds in his dad's garage, pulled the bullets, burned the powder, then taped the primed brass on the ends of our BB guns. The primer came back and destroyed the end of the barrel.
Another guy I know (old enough to know better- he was retired at the time, he's gone now) sat a shotgun shell on a fence post and shot it with his pellet rifle. He had to make a trip to the hospital to have the primer surgically removed from his arm.
The fun we used to have. The things I did as a kid that my kids will not be allowed to do. I'm no safety nazi, but I put my foot down when it comes to "fun" that can kill you.
I would say it's amazing we all survived, but some didn't. The difference between a close call that everyone laughs at and a terrible tragedy is often a very fine line.