Ive shot out barrels. Depends on the caliber how long it takes, the barrel material, and how much idiocy was involved (friends dont let friends lap their barrels). Also depends on how picky you are - I hold on longer than I should. The rifle is fine, though its no longer my match gun.
Got an old IPSC .45 thats pretty well shot out. I got it second or third hand in high school, then proceeded to shoot the piss out of it. Always a poor situation for longevity, a range within walking distance. No idea how many rounds been through it. Its as loose as Paris Hilton, but better looking.
Buy it, shoot it, rebarrel it if you have too, or you might get away with chopping and re-cutting a chamber. I use .223 to varmint hunt, and the Savage I bought as a temp fix still corks em, after more than 10 years. Little less then 4000 rounds according to the pilot.
After so many explosions, metal fatigues, deforms and erodes. If you shoot enough, you'll need to fix something - the reciever will be around longest, dependent, but eventually it'll go too. Part of the fun.
Luck
Alac