FYI: the Martini Cadet has a thread size of 0.750", considerably smaller than the small wall size. The Cadet is a proven performer with the 44 Mag and the 223 Rem, and seems to become marginal only when cartridges exceed 45K psi and 0.420" dia. The 0.375" dia 50K psi 223 is OK in the Cadet as is the 0.457" 40K 44 Mag so I figure that either would also be fine in the small-shank high wall.
Here's another approach: Ackley figured that a steel wall thickness of 0.125" was the absolute minimum required for containment of a 50K psi '06-size cartridge, so add 0.470" + 0.125" + 0.125" for a total dia of 0.720". Now, we know that the Cadet with its 0.750" thread is unsafe with this large a case at this pressure, but we also know that the small-shank high wall is much thicker and therefore much stronger; question is, how much?
My own personal opinion based upon many years of messing about with walls is that a small-shank high wall with a modern steel bbl would handily handle a 225 Win (0.420" dia, 50K+) or a 30-40 or 303 (0.457" dia, 42K) but I wouldn't want a 308 (0.470" dia, 50K+). Please bear in mind that I'm a serious hot-rodder and I don't hesitate to push the machinery to its limits, so IMO you should probably consider my suggested limits to be the absolute maximum sanely advisable. JMOFWIW.
Good luck, Joe
