This barrel is on a .45 caliber cap lock that was made by me in 1973 and last shot and cleaned in 2002 before I went to shooting flintlocks most of the time. The barrel was wiped with WD-40 before it went into the safe many years ago. I recently purchased a Teslong bore scope and wanted to see what this gun's barrel looked like after all these years. Here is what I found; The breach area looked good except for the drum threaded hole which showed some strange amber "gunk" around the hole. The lands looked ok but there were some strange amber streaks in the grooves it was not rust. My guess is that it is WD-40 that has dried in the grooves and turned into some kind of varnish like residue. It is tough to remove with only a patch on a jag. I tried some 4/0 steel wool but the brush with the steel wool wrapped on it did not get into the corners of the grooves very well as seen in the picture. I am learning how to use this bore scope and hope my pictures will get better in the future.