Some time back I bought a bunch of very old gunsmithing equipment. Amongst the pile was a sucrets box full up with rifling files and 20 or so arbors in all different calibers. Very little info on the web about these but as I gather they were frequently used on older barrels with soft steel and when the rifling wore out from shooting or cleaning these were pushed/pulled through the bore by attaching to a shaft akin to a cleaning rod. The arbor that holds the files are bore diameter and the files are slightly canted and are placed into the bore one groove at a time. You would make passes on one groove then remove the tool, rotate to the next groove and repeat. Once all grooves were gone over one pass then you would adjust gib screws under the file to increase the diameter of the tool and repeat afore mentioned process until you had deep rifling.
This process did not file the lands but only the grooves. Once completed, you simply sized your bullets larger afterwards.
From my readings, this as common practice with schutzen matches and some would do this after every couple matches.
As life goes on I find myself acquiring older rifles and sometimes with poor bores. This may be a reasonable alternative to sleeping barrels.
Has anyone ever seen these tools? I didn't take any pics but will this weekend. Also have no idea as to there worth but have no interest in selling.