A cautionary tale.
When I were a lad, we made fireworks ourselves.
We used sodium chlorate (weedkiller, tell the bloke in the shop it's for your dad's allotment) mixed with sugar and shoved it in cardboard tubes, put a bit of paper in the end and lit it.
My mate Chris and I were putting them in the old air-raid shelters at school for laughs and he got caught, and I didn't.
He got sent home for four weeks which was a bit unfair.
Anyway, Chris decided to go one better, what with all that free time. He put his in copper pipe. He was hammering the end over, holding the tube in a vice in the shed.
His neighbour saw that the shed roof had come off and went round to see what was going on. Seeing that it was a bit of a mess, he wrapped a teatowel round my mate's hand and called an ambulance.
I visited Chris in hospital. He was short of an eye and four fingers on one hand.
I don't make my own any more. I strongly suggest you don't either.