The one caliber rule is the safety rule used by several cannon shooting organizations for replica cannons shot in their competitions. Absent any other established safety regulations we point to these organizations rules as a guidelines for minimum standards for building cannons. It is a place to start especially for some one not all that familiar the types and steel an their properties.
We are well aware that that modern steel is perfectly capable of sustaining much higher pressures such as your Bofers barrel.
The rule is not that simple however. You will find links to the rules here:
Safe Loads and Construction There nothing wrong with building a cannon from your Bofers barrel with thinner walls. For our purposes here on the board we deal only with pre 1899 replicas and antiques. As long as you gun meets that description you can discuss it. It is not a requirement to discuss it here that it meet the 1 caliber rule.
