Sometimes it is better to leave it dark rather than clean it up. My buddy David had a Spanish Mauser that was one of the most accurate surplus rifles I've ever shot. The bore, however, looked like a dirt road after a stampede of diarrhretic cattle. His uncle gave him the rifle and neither one of them had ever cleaned it. After talking to me, he decided to clean it. Turns out the more was mostly potholes and burrs and all the gunk had filled in the problems. It went from quarter-sized groups at 100 yards to pie pan-sized groups at 30 feet. It took nearly 400 rounds of shooting without cleaning for the fouling to fill enough divots for the thing to be gallon-of-milk accurate at 50 yards.For sure Cyrano. I say scrub the bore too. I have seen dark bores clean up before. Also a dark bore can still shoot accurate. Like you say about easy to find a Chicom SKS. Not so on a Mauser especially an Israeli one.