I've been deep-cleaning an M1 Garand I bought a while back. The rifle's condition when I broke it down was a little puzzling. I found almost no grease residue anywhere, leading me to believe that the previous owner might have intended it as a wall hanger -- the rifle does look good and shows very little wear for a 1942 serial number. So I expected the entire rifle to have been cleaned and de-greased ... but ... when it came time to clean the barrel, it looked like it might not have been cleaned since 1942! I scrubbed thoroughly with a brush and ran a number of patches, which kept coming out filthy black. I finally re-brushed and re-patched and got it down to the point where the patches were not completely foul. Then I ran a soaking patch through and let it sit while I cleaned other components. When I came back to it, the first patch through came out solid green! I re-patched a series and repeated the soaking set-aside as before. Same result! Then I did it again, except I waited for hours. Same result! Then again, except waited overnight. Same result! A visual inspection shows a clean bore, but the patches tell the tale. Ordinarily, I'd say "copper fouling" and keep cleaning. But doubt creeps in -- I've run a bunch of patches and scrubbed a bunch with the brush. So what say you CFF experts? What is the residue and what -- if anything -- do I need to do differently to remove it? Thanks!