https://www.snipershide.com/shootin...n-barrel-break-in-procedures.27321/post-27321
The portion of the main post that is most relevant to this discussion:
Cleaning rods can and will damage barrels if you overclean. Even using proper bore guides, rods, and jags you cannot entirely eliminate the possibility of damaging the bore or crown of the barrel during cleaning. Brass is softer than steel and that makes it unlikely to scratch or damage the barrel, yes. Sapphire watch crystals (used for the face of high end watches) are a 9 on the Mohs scale, and yet in time even they will scratch after repeated contact and wear with other materials. It's not a matter of if, but rather when the barrel will be damaged - however slightly - by cleaning rods.
The goal is to minimize the chances of this happening and limit the potential damage done if it does occur. The potential damage is limited by proper cleaning procedures and equipment. The chances of it happening are limited by avoiding overcleaning. If you're lucky and use good technique/equipment your overcleaning may not damage the barrel enough to have any effect on accuracy before the barrel is cooked anyways. If you're unlucky or don't use good technique/equipment you will degrade the barrel's accuracy potential before it is shot out if you overclean.