barrel wear

[The Virginian]

Many older bores were ruined not by bullet wear, but from overzealous cleaning or lack of cleaning after shooting corrosive ammo. As the others stated, it takes a lot of rounds to ruin a barrel even with regular jacketed rounds it will take 10s of 1000s and with lead it might be 100K. Heat also plays a role at the rear of the barrel, but more so with with rifles than pistols. This assumes that the barrel is also properly cleaned and oiled between shooting sessions and is not neglected.