Just a little thing, a casing can be a matter of life and death. Refrain from using metals, as they are extremely dangerous, not very flexible, react with peroxides and with HMTD. Also, a little side note, a friend of mine made a really simple explosive. AP, in a bottlecap, duct taped up to the size of a lime. He had 3. they had a charge of about 2 grams, no fuse, we did the first 2, by making an ethanol wall of fire, igniting the ball, and the fire took about 4 minutes to make the AP explode. same goes for the next one. the third one though, we thought we had time, so i light it, and the instant i flick my lighter, it blows up, and im covered in shrapnels of duct tape. whisling in my ear, i look down to my hand. the metal plate on the lighter is lodged in my ring finger, my middle fingers nail is not there anymore. my thumbs skin is ruined. blood collects under the skin, it swells up. my friends are shouting at me, i dont hear it. adrenaline rushes through my vains. i wander aimlessly, shocked, to notice my glasses are shattered. a triangular piece of bottle cap is stuck in my sunglasses, which shattered.
in the end i was ok, just my thumbs fucked, and my nails really ugly, but other than that im ok. but recalling, i was covered in duct tape bits, maybe 2by 2 mm. now imagine all that were metal.
all im saying is that you still get a bang with flexible materials (ballon inflation principle) often even louder than with metal. (think how much gas you would need to pop a ballon made of metal).
keep safe kids.
Random says: This is why safety is important...