As mentioned by other posters....
Many "burned out" .220 Swifts are really just severely copper fouled. A thorough cleaning can do WONDERS.
On the subject of barrel life... Here's a quote of mine, from another thread, where we were talking about the different manufacturers of Ruger barrels in the past:
FrankenMauser said:
I have a 78 prefix tang-safety M77 that was originally chambered for .220 Swift. I have no idea whose barrel it was (but it was of ~1983 production), but it shot like a dream. And that barrel, 4,500+ rounds later, is still going strong on another 78-prefix M77 tang-safety, in the hands of a predator control contractor in Montana.
If you take care of the barrel, it can keep going strong for quite some time.
Fun cartridge. In my opinion, the "barrel burner" label is mostly unwarranted (it's the way they're shot that kills some rifles so quickly - not the cartridge itself). But... It can be a bit of a pain to reload.
I don't plan to ever own another one.