The pipe is MDPE which is used in pressurized water installations and i have tested this kind of pipe up to 12 bar and it has never moved which is a lot more than pvc would take but the fittings are not as easy to come by hence the stopped end rather than screw off end. the combustion end is 250mm ...

Help please
I have built a very basic cannon out of MDPE black sdr11 pipe work. to create the chamber though it had to be enclosed ( the back does not unscrew) so to get the fuel in (propane camping gas cooker ) I drilled a 1mm hole in the chamber where I can spray the gas. It worked the first time ...