The Big Bang Cannons are quite solid and robust. I have 3 of the larger ones, and even a gold tone one! However, I haven't tried H2O2 in place of H2O. I will though and let you know!
I've been shooting them since I was about 10.
As Luke said, the acetylene mixed with air in the reaction chamber makes for a 12guage-type bang. The chamber is made of thick cast iron. The barrel is just formed steel. The smaller ones' chamber and barrel are one-piece cast iron. They're just not as loud.
Someone once called the police on me and my son. By the time the two police cars left us, the cops had fired the cannon at least 10 times! Kinda neat.
I gave one of them the website and an old brochure...

Allen