Re: most cost efficient?
I never heard of a $900 barrel? Maybe after it's chambered, buying a muzzle break and having it installed you might get close to that.
Like Jim said, look through it with a bore scope, if only the last few inches are bad cut and recrown, $40 would take care of that. If you need a new barrel you can get any top of the line barrel for $300 to $400. Kreiger, Bartlien, Broughton and the list goes on. Chamber job form a good smith should run somewhere around $200. But now that you're looking at a new barrel you'll want to figure getting the action trued up, Lugs lapped and that list can go on for a while too.