I am slightly familiar with the guidelines of the American Artillery Association and the North South Skirmish Association. I see they have recommendations as to load size as related to bore diameter, but I do not see where there is a reference to wall thickness or type of material.
This is copied from this website:
1. Powder charges should not exceed 2 oz. of Fg or 3 oz. FFA or Cannon Grade Goex powder per inch of bore diameter. No excessive charges. Use black powder only.
I'm sorry but I didn't see any reference to wall thickness of material type. Could you point it out to me?
You must not be that familiar:
N-SSA Skirmish Rules10.2 ELIGIBILITY
Actual or exact scale replicas of Civil War artillery pieces may be fired. The term “Civil War” applies to any artillery piece whose model antedates April 26, 1865. Replicas of artillery pieces must duplicate original pieces. All reproduction barrels must be made of iron, steel or bronze. All reproduction barrels and those original barrels failing inspection must be lined with a bore liner of extruded seamless steel tubing of a minimum ANSI standard and of a minimum 3/8-inch wall thickness.
Figure 10.1
The liner must be closed at the breech end with a steel plug, sweat-fitted into the liner and welded. The breech plug must have a radius of at least 25 percent of the bore radius and be at least 1 inch thick at its thinnest point. (See figure 10.1). All reproduction barrels manufactured after March 1, 1986 must have pictures of the liner and breech plug before and after welding. No reproduction barrel shall be approved after March 1, 1986, which does not have one caliber's thickness of metal surrounding the bore at the breech. (See figure 10.2 for example.) Liner may be affixed by casting barrel around the liner or by other approved methods such as bonding with high strength adhesives. The method of locking liner in barrel shall be approved by the Artillery Ordnance Officer. The gun and its crew must pass the inspection specified in Section 18. A gun crew shall consist of a minimum of 4 members of the organization. Effective 1 February 1996, all artillery pieces must be originals or full-size, exact replicas to be approved.
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AAA is not quite that specific.
Safety Rules and Procedures for Shooting Muzzleloading Artillery,
of the American Artillery AssociationGENERAL INFORMATION
The following safe shooting procedure presumes the crew is firing blank charges or projectiles with a muzzleloading artillery piece made (or altered) to modem safety standards. (If firing blanks skip Step VII and see Safety Rule 10.) The bore should be lined with seamless steel tubing with a minimum 3/8-inch wall thickness and a yield strength of 85,000 p.s.i. or greater. The breechplug should be threaded and pinned; welded and pinned breechplugs can be equally strong but require expert installation by competent manufacturers. Sand-cored bores are not recommended for shooting. The vent should be drilled in a threaded copper bolt similar to original cannon vent liners of the 1840-1865 period in order to provide an unbroken passage through the casting and the liner, into the bore.
By the way those link in the safe loads and cannon plans sticky point are these same links above.