Are you trying to sell it fast? Go on gunbroker, compute a low average price for the gun based on existing listings, but don't include puds in the average (because, well, f*** puds) . Take the gunbroker low average, then take 100 bucks off that... list it firm for that price. (because you probably have a used gun) and if your gun isn't crap, it'll be gone in a week unless its something totally undesirable. If you can't afford/stomach to take 100 bucks off average low of the new prices, it's going to be very difficult to get buyers so it's not even worth listing, unless we're talking about something that's actually rare or hard to come by. (but then if it was, you wouldn't find comparables on gunbroker to set the pricing... )
-Mike