I remember doing something very similar many many years ago.
My school pal and I dissected one of his Father's shotgun cartridges to harvest the BB shot from within to use as fishing sinkers.
Inevitably we were left with the empty primed case.
The primed case was duly secured in his Father's vice in the garage and was belted with mallet and nail.
The resounding memory was one of shock as my eardrums reverberated with the explosion which was way and beyond what either of us considered possible.
Shortly afterwards both our arses further resonated as my chums Father exited the house like a greyhound on acid thinking we had blown up his garage. . . A thorough belting ensued !!!
That was almost 25 years ago and I still remember the look on his face as he bolted towards us like it was yesterday