Linotype metal at brinel of 22 (21 for reclaimed lino) nor Monotype metal at a brinel of 24, will not harm your bore, not even a 12L14 bore. Hardened WW metal at a brinel of 30 to 33 will not harm your bore as the cloth patch will protect it. Indeed, even if it scrubbed your bore full length, it would not harm the bore. Dead soft copper has a brinel of 34/35 & it will quite likely not harm your bore, either.
Powder gas blow-by, however, is harmful due to the flame running at cutting speed past the patched ball. This powder gasses flame "cutting"also happens in modern barrels with undersized projectiles.
Indeed, cloth or paper patching is likely more wearing to your bore, than is lead of any hardness.