Thar's a few thangs I'z seen here what "concern" me, but maybe it's jist the "engineering" in me poor misguided life.
#1 - The use of old gas cylinders is a concern. They are probably better quality steel and fabricated with more care than most "scrap yard" findings, however they were never intended to withstand the kind of pressures and shock loads that they are subjected to when launching a projectile with blackpowder. The highest gas pressures I am aware of (without looking them up) and in the 3,000 to 5,000 PSI range (diver's cylinders). Figures I have seen for "internal bullistics" for blackpowder are in the 30,000 PSI range for a blackpowder rifle. I have no idea what actual pressures may be involved in launching a bowling ball over 300 yards. (My physics is too rusty or I would attemp to calculate it!)
#2 - "Pipe" isn't just "pipe". There are all different grades of pipe, from "black iron water pipe" (which can be garbage made in India and barely able to withstand 100 PSI) to certified high pressure pipe. For example, the 14" diameter, 3/8" wall pipe used in my steam engine barrel is rated 1,400 PSI Steam and (if I remember right) about 5,000 PSI gas.
It scares the he!! out of me when I see people using "unknown materials" in critical applications ("critical" meaning where life or property is at risk).
I suspect that these people have no comprehension of the forces involved or of the carnage that could result from a failure. Does anyone remember the steam engine explosion in Media Ohio? Can anyone spell "law suit"? Look up "schrapnel" and then tell me again about building a cannon barrel from "unknown material"
JMHO
