I did something similar when I was a kid.

I got hold of some rim-fire cartridges, and used pliers to pull the bullets out, then used a needle to pick the propellant out of each one so i had a little pile on the desk.

You can probably already see where I'm going with this. One cartridge I picked a little too hard and the resulting explosion set the pile off. The bang was huge, fortunately my parents were out and didn't hear it - or see me stumbling around half blinded with a blackened face, and blackened and throbbing hands. The cartridge I'd been holding looked like a half peeled banana, and everything on my desk had been blown across the room in all driections.

Thankfully I was more stunned than hurt, and managed to clean everything up so nobody found out!

I don't do anything like that these days, though in recent years I confess I may have inserted large fireworks into large pumpkins to vaporize them.