I'll quote it here, pages 201, 202 from "Hatcher's Notebook":

"The late Sir Charles Ross, whom I knew very well, had told me about his experiments on the thickness of barrels, and I had read some remarks by Newton on the same subject, but I couldn't get sufficiently authentic facts to satisfy me, so I collected some firsthand information by turning down a Springfield barrel to 1/8 inch wall thickness and firing it with regular and high pressure cartridges. As the results were not visible, I turned the barrel down so that it was only about 1/16 inch thick over the chamber. It held three regular service cartridges perfectly. I then put a 75,000 pound shot through which blew a piece out of the side, as can be seen in the photograph. As the thickness of the regular barrel at this point is 5/16 of an inch, it is plainly evident that the strength should be sufficient."

The photo is included in the book.

No mention of rifling forced to the outside of the barrel.

BTW: I think Gryphon's idea is brilliant! High speed photography would at least show the semi-fluid, vibratory, whipping nature of a barrel subjected to the effects of the firing of a shot tho if OSR is cumulative any single series of photos might not show it clearly.