I couldn't tell you
All I know is I grease cranes for a living and I have seen the damage that is done when a brass journal bearing becomes contaminated and eats a hardened steel shaft......
IF I was going to do this on a regular basis I think at the very least I would be very careful to clean the brushes very after and/or, as a previous poster mentioned, change to new brushes or mops as soon as they appeared to be getting dirty.....John
On that first part I totally agree. And in fact this is why lapping operations always use laps of a metal or plastic that is softer than the item being lapped out for finish and clearance. The grit embeds into the softer material and can then work as if it were sandpaper on the harder one. A hardened steel pin running in a cast iron body will generally wear out while the hole in the softer iron body is still sized to spec for this reason.
The thing is that the fouling we get in our guns is not abrasive. It just needs to be chipped away to remove it. And the crud ring in the cylinder left from shooting a lot of shorter .38Spls is in that boat. So doesn't embed into the brush and produce wear the same as a hard grit would do in the case of sand getting into those journals. Plus we're flooding the brushes frequently with cleaning solvent during the cleaning which again aids in keeping them clean.
On the other hand any bore brush that I were to use with such polishes as Mother's Mag Wheel polish, Flitz, or JB bore paste would be set aside and clearly labeled as "Contaminated with ###X Abrasive Polish" where ###X is the type of polish. THOSE items ARE abrasive and will embedd their abrasive particles into the softer bronze wires of the brush. The only reason to keep them is to re-use them at some point with simlar other abrasive polishes for whatever reason.
