Yep, I forgot to mention that! If the pin is rusty and/or pulled out quickly, the heat or spark can set them off in your hand. Been there as well!
Your post reminds me of seven year old twin boys we had in the hospital where I used to work. They had somehow found some gun powder in the attic of their grandmother's house. They took it outside and played the Road Runner cartoon, placing two long lines, and then lighting it with kitchen matches.
They were hurting for a couple of days, but not seriously hurt.