I would not buy it based on the seller's claim that it "shoots just fine." Is that "just fine" for a 2 yard self defense expert or accuracy that would please a good target shooter? I would have to test it myself and even then, why spend my reloading money and time on a gun that is inferior to my others?

I'd start by calling Ruger and asking if they have barrels and if they do what it would cost to have them replace it. If they will not do it I'd consider having the local smith shorten it to 3" or 4".

Parts kits from guns that municipalities destroyed are commonly sold on eBay. Some entrepreneurs buy the kits then separate and resell the parts. You could probably find a barrel. Unfortunately the gunsmithing charge for swapping barrels is in the $100 to $150 range. Also there are risks. Generally scrap barrels are not thrown out after they are replaced. They get tossed in the gunsmith's or the gun owner's odds and ends box then eventually resold as good barrels by who ever winds up with the box after they're gone. You might not learn the used barrel is defective until you show it the the your gunsmith. Also the gunsmith might do bad work. (Guess how I learned this stuff.)