Colt seems to think its a problem and says that if you dont clean the carbon off the bolt tail, you will eventually have a failure. Hope it's not when it counts. I got a different tool that cleans off the carbon by scraping, then polishes off all the little bits that are hard to take off. It only takes about 20 seconds to do the whole thing and man it looks great. No failures either. It's made by GNG tools and for $27 bucks it was worth every penny.