Yes, I used the anglocised acronym to avoid confusion, but doing so I created it. Oops.
The CIP sells a series of technical publications-decisions and among them is one with the minimum barrel thicknesses for the three ISO types of steel the Commission says are most often used for shotgun barrels. Note that this is a recommendation and not a binding rule. In other words a gun can still be submited for proof and will be stamped as proved if it passes even if the wall thickness is less than any specified in the recommendation.
