Keep in mind the standards cited by Dom in that post are original theory's and practices. The safety rule 1 caliber wall thickness over chamber, that we cite here on this forum come from the modern standards established by the North South Skirmish Association. We cite it as a baseline rule of safety.
It is possible to safely build a cannon with thinner walls if you know how. Since not everyone has the same level of skills and knowledge and we have no control over who reads or uses the information posted, in the interest of liability it is our policy here to cite the one caliber rule and N-SSA as our authority.
If you use less than one caliber wall thickness, then you better know what your doing.
