Colloidal Graphite in a isopropanol carrier. This is a dry film lubricant. This is the product that I coat every new barrel with that I install. This product fills the micro structure. So you have a graphite lubricant in the micro structure, instead of copper and carbon. This helps to prevent the fowling from sticking to the bore, and get a longer shot count before needing to clean.
I break in all my barrels by coating after every shot & cleaning. This makes sure the micro structure is filled in. I have a 17 Ackly Hornet that I put over 1400 rounds through this summer & fall on squirrels, and have not cleaned it yet because I'm still hitting what I shot at.