Inspection of bores:
1. clear, sharp rifling lands and grooves. shiny/reflective bore is desireable. dark bore indicates pitting and corrosion damage.
2. no muzzle crown damage. rifling damage near muzzle ruins accuracy.
3. no bulges, rings, or dark spots. These are not reparable. replace barrel.
4. no chamber pitting or damage from prying out stuck cartridges.
5. origin of rifling ("leade") and bullet seat unworn or damaged.
Rimfire bores are almost NEVER worn out. They get damaged from careless cleaning or neglect.
HTH
John