well, it depends ... (trying not to sound like a lawyer, here)
an entire rifle for that price is not too shabby, but if barrel is a mess, you have to take a look at replacement, and now you're looking at another hundred or two, best case.
I would advise you to try the 'Persian rug merchant' negotiating technique: peel off a trio of twenties and ask, now, the bore of this gun is a mess, and i'm gonna leave this money on the table for only so long. you and I both know that this rifle is gonna need a boatload of work. pull out another twenty and point blank tell him, "I won't go another - whatch wanna do?"
if you're not willing to walk away, keep your wallet in your pocket.
(p.s. - I learned this from my wife, who - I kid you not - has brought used car salesmen to tears ... to watch her negotiate is a thing that borders on the scary).
well, that's one guy's advice ... free and doubtless well worth the price ... good luck with the art of the deal, and let us know how it plays out!