I never have used JB until yesterday but I have a couple of questions. I was cleaning my 300win yesterday and I noticed right where the throat starts there are what looks like tiny salt grains (which we all know it is not salt) in a ring top to bottom. I shoot Retumbo in this rifle so I am guessing it is carbon. Well I took some JB the grayish brown stuff and ran 4 patches through there with about 5 to 10 strokes each. The patches came out black but the specs are still there. I let some GM top Engine cleaner sit in there for a half hour or so but I can still see little specs. I also went after it with a Brush but they do not seem to want to budge. So my question is do I dare use some more JB patches? Or could it be fire cracking that I am seeing? I have not shot the rifle on paper for over a month but last time I did shoot it the accuracy was good as normal. I did notice when I ran Kroil or GM through on a patch it really seems to stick to what ever I am seeing in the bore. The specs I see only go forward twords the muzzle about the thickness of a dime or a little less. Any advice?