Bushveld, I think you underestimate the magnitude of concentricity problems.
The technology to address that economically seems to be fairly recent.
ClapperZ;
Thank you for your comment.
However, I was not considering the concentric bore versus out diameter of the barrels(such as Holland's has focused upon and corrected in its barrel making) but was stating how the barrel's bore id could be changed beyond the 9 inch standard position for measuring. Such a bore diameter issue could arise for instance from an ill advised "gunsmith" taking too much bore away after hammering out a deep dent into the barrels, but the barrel was still in proof.
However, the wall thickness gauges and inside bore gauge technology existed before the 1954 proof rules, i.e. the electric power steam tubine generation industry in measuring condenser tube wear for one example; and which England via Parsons turbines led the world from about 1900.
My own English made barrel bore gauge must go back to the 1960's.
Maybe Hugh Lomas could shed some additional light on the age of the technology as I remember Jack Rowe saying that Hugh was educated and trained as an Engineer in the UK, before he came to America as an Engineer. I also remember Jack having a very very high regard for Hugh and his gunsmithing. I wish Jack was still here to guide us in this discussion.
One of Jack Rowe's career time frame fellow gunsmith, Malcolm Cruxton of Price St. Birmingham is still living and working in his Price St. workshop. I may send him and e-mail and see what he can tell me about the subject. He was going to Thailand for the Christmas holidays and beyond; and he has likely returned to Birmingham by now.
