I have seen some bushnell elite 6500's used in the 500 price range. He'd be better off trying to shop used to get a little more glass for the money with a 500 budget. In my opinion once you start going above 12-14x mag glass quality starts to show its face in lower priced scopes. If he wants to use the 20x plus mag often and not be dissatisfied by clarity then trying to find a 700-900 dollar scope on the used market for his budget will be a better experience.
If he doesn't mind a heavier scope there are some good deals on gen 1 vortex viper 6-24's right now.
If he doesn't mind a heavier scope there are some good deals on gen 1 vortex viper 6-24's right now.