Just for a point of reference, anything that is black and comes out with any amount of patch solvent and brush work, is by definition, not what is colloquially referred to as "hard carbon". So, for those of you that are so concerned with the use of abrasives, do you just ignore the stuff, or do you not own, or have a friend with a bore scope? Barrels are like the tires on a race car, they should be well maintained, but they wear out. The usual cause of this demise is from heat checking that starts at the throat and progresses forward. Using abrasives requires some attention to both having the right equipment, and technique. If one uses abrasives excessively, or improperly, it is possible to damage a barrel, but if one is reasonably adroit in their use, they can be useful, and will not harm a barrel, within its useful accuracy life. The need to use abrasives is dependent on several variables, of which, an important one is what powder is being used. For example, in the short range benchrest area, 133 has been and continues to be a very popular powder. In my experience, one can clean its fouling without using an abrasive. On the other hand, some other powders that have been popular require their use.