I bought a Mark X Mauser 30-06 that was made back 30 or so years ago. It did not appear to have been fired. I have fired 6 or 8 rounds thru it. I did not observe anything in the barrel before I shot it--I did look, in fact I ran a patch or two thru it. There is some sort of substance coating the bore in the first 6 inches or so from the chamber. It does not come out with Hoppe's #9 unless I use a bronze brush on it. I have about wore one brush out trying to get rid of whatever it is, it just seems to dirty the oiled patch after brushing. The gun is very accurate, so it does not seem to hurt anything, but I like a nice clean bore. The rest of the bore is pristine. What could this be? It does not appear to be rust but maybe that is what it is. It appears that there was a thin coating on the first few inches of bore and it dried out over the years and Hoppe's does not cut it. Any ideas?? Thanks.