Bill;
In the model making shop I worked in a fellow machinist had a very large piece of steel in a lathe making a sting which would be used to mount a model in the wind tunnel. He had the large end of it chucked in the lathe with the small end in a steady rest & was tracing a taper in the mid section. He was running a water based soluble oil coolant at the tool when all of a sudden coolant began running out the bore of the part. Seems the steel had a large interior hole in it. Steel had been procured from a source approved by the customer & supposedly Certified. The steel company of course replaced the steel, but we lost a bunch of man hours in the process.
Of course when smaller pieces of steel are drawn or rolled is when "Seams" are formed rather than a hole as in this case. The worst of these will be caught in machining or the proof testing but others are hidden & will pass proof & may never present a problem, depending upon their, size, location etc & the thickness of the wall where they occur.
As stated though this burst could have been from either an internal seam or from a thin spot being created in the striking next to the rib. In either case it my well have never burst had not the obstruction bulged the metal beyond its tensile strength. Had not the weak area been there the obstruction "May Not" have burst the barrel but only bulged it.
It would of course take a hands on inspection by a knowledgable person to make an absolute analysis of the cause. Much reasonable thought & possibilities have been discussed here. Of course from Wonko the "Insane we have heard only Noise & Static.
