well - true - the bore size is determined - as stated by the Birmingham house
"(ii)
Each barrel shall be gauged at a distance of 23 centimetres from its breech face for its bore diameter, which shall be
within the limits set out in Table 1A ofAppendix I for the diameter of such barrel. "
but that is strictly for determining the bore size - that states nothing about the wall thickness at that area.
20 thousands 9 inches from the breech would scare the heck of of me
To quote Mr Greener from our recent converstion
"
Barrel wall thickness measured 9 inches from the muzzle end of the barrels should not be less than twenty thousandths of an inch. But the policy, of most gunmakers, is not to sell guns with barrel wall thicknesses less than twenty-five thousandths of an inch, "
Threaded Mode