Me and my friends had a lot of fun as teenagers using aerosols for a similar purpose. We'd scavenge old aerosols from our parent's houses and use them as the pr

Me and my friends had a lot of fun as teenagers using aerosols for a similar purpose. We'd scavenge old aerosols from our parent's houses and use them as the propellant for spud guns and the like (we didn't blow up any cars, for the record). I think the trick was to find the ones with propane propellant rather than butane. I also suspect that the (rapidly boiled) moisture droplets from the aerosol would have added to the explosive force too. Eventually we decided to go straight to the source and got ourselves a little oxy/propane welding kit. That worked a treat. I'm kind of surprised B&Q sold that to a bunch a teenagers actually.