With no intent to make this a personal quarrel and the caveat that I am an engineering school dropout, I beg to differ with the opinion that a 3/8" thick wall would be adequate for this application.
The AAA/NSSA barrel rules are talking about a 3/8 liner inside a cast iron or bronze tube which provides extra strength that would not be present in the design under discussion unless the space between the inner cylinder and outer cylinder is filled with some kind of material of significant strength. As is usual in discussions of this type, we are missing the critical parameter of chamber pressure and thus are limited to speculations based on more or less relevant pressure figures from previous tests.
SO,
assuming a filled one pound charge chamber (volume 24.25 cubic inches) and a chamber pressure of 20,000 psi (taken from the M. Switlik tests of 25 years ago), and using the thin-wall cylinder stress equation from
efunda, the first inch of the tube would experience approximately 3650 psi resulting in a stress of 63,000 psi. A filled two pound charge chamber would give 7350 psi pressure and 127,000 psi stress, which is clearly way too much.
Now these calculations are about as simplified as possible but increased complexity only makes small changes in the results. So another step in the design process needs to be taken, namely deciding what the powder charge is going to be.
By the way, the tensile strength of concrete is very low, less than 1000 psi.
