I found this Lead/Carbon "Wonder Cloth" at the gun shop and decided to use it to polish my Sig 220 (it has a beadblasted finish, and now has a mirror finish).  Normally it's only for stainless / nickel finishes, but I figured, "Hey this AR upper is a piece of crap...what the hell".  Well it seemed to do an excellent job at fixing up scratches and making dents much smoother, without causing any problems with the finish on there.  Looks like a good "trick of the trade" for fixing up minor blemishes on AR's.