Gary, I agree with Rockstar. The Glock barrels will last almost indefinately with jacketed bullets due to the tennifer treatment that is on the outside and inside the bore. The same can be said for the HK poly rifled bores. Unless you run into a situation where the super hard layer flakes off, which is rare but not impossible, the first things to wear out will will be the locking block and the bore in the slide that supports the muzzle end of the barrel. The locking block is easily replaceable, the slide will not loosen up enough to be a problem if lubricated for many tens of thousands of rounds. If the tennifer flakes Glock will replace the barrel free, they did for me anyway.
Glad I was able to help.