Bowser. It depends on the model. An International, yes. The standard 77 without iron sights, not really, unless you really want the gun. With sights, maybe. I had the standard rifle, without sights, and I loved it. Traded it off to a guy who did not like his International,because he felt he lost too much velocity due to the shorter barrel. You don't lose that much.
You did not say if the rifle was scoped. If so, that $500 would not be too out of line, depending on the scope.
If it was me, and I wanted it, I'd offer the guy $400. If he counter offers, offer to split the the difference and go $450. A lot of times, I'll ask the seller what his rock bottom price is, and end up with a good deal. I can't hurt to try.
Paul B.