I almost hate to post in this thread, but some added information is useful:
First, to answer the OP's question, get a container of Slip 2000's Carbon Killer product. It will dissolve the carbon off and you can wipe it away with a paper towel. No. Wait. Paper towels are abrasive. Use a soft linen rag. See the cylinder photo on
the second page of this brochure. If any of you own an M1A or M14, you know how carbon cakes up in the gas piston. This stuff actually removes it, though I did find it has to soak for awhile to soften it all. Bottom line, though, it works as advertised. The only caution is that it also gradually attacks Parkerizing, so don't leave a Parkerized part in it for more than the directed 15 minutes. I left a Garand op-rod tip in it for several hours one time and the Parkerizing no longer matched above the water line.
I used a lapping ball to put a mirror polished crown on a Garand rife barrel by stepping through abrasive grades down through polishes. It was so sharp, I couldn't push a patch through it from the muzzle without it cutting a .308" disc our of the patch. Then I shot it a few times. I was not longer mirror polished. It had fans of matte surface that started at the edges of every barrel groove, where the gas starts coming out first. The powder's gas and particle products were abrasive enough to undo my polishing. It no longer cut patches. For that matter, the throat of the first barrel I got with my Dan Wesson V.15 has no toolmarks left because using 296 has abraded all that away.
So, if you don't want any dull or rounded corners, don't shoot the gun. Many powders are more abrasive than polishes, though none are as abrasive as coarser grit abrasive materials are.
You can find the patent on lead wipe cloth at uspto.gov. I did that once, but have mislaid the patent number. If you find it, you will learn it uses 400 grit aluminum oxide abrasive embedded in the cloth. That is far coarser than any polish. If you swipe it over a piece of polished aluminum, you see the fine surface scuffing immediately. I can see the same abrasive wipe marks in the cylinder in the photo supplied earlier. That said, aluminum oxide is rounded edge, slow cutting abrasive. It would take awhile to wear much depth away with it. The inventors of the cloth simply decided it made an acceptable degree of appearance change.
Polishing isn't mechanically quite the same as abrading. A lot of studies have been done to show the mechanics change when abrasive gets fine enough, and the surface you are working on flows. They have found particles of jeweler's rouge polish in glass lenses that are actually
under the surface of the glass. So the glass was flowed and smeared over top of it, kind of like icing a cake. Removing a significant amount of metal this way would take a very, very long time indeed.
Everyone seems to have forgotten silt. River water contains sand and silt and the river flows these abrasives over rocks constantly, picking them up from tributary streams which have rain carrying dirt into them. Absent that, I'm sure the water would have a hard time wearing down some kinds of rock other than by freeze/thaw cycles. Impact by water will eventually fatigue the rock, but it would be a lot slower than the effects we see from sand and silt.