Is anyone aware of a website in which you can look up a value of guns? I'm looking for something similar to Kelley Blue Book for cars in which I could look up a gun make and model and see an estimated price or value.
You might try checking out one of the gun auction sites for a comparable arm and see what they're asking/bidding on those. You might also do an Advanced Google for the specifics of your arm to see what comes up...add the word "value" to try to winnow out prices. Good Luck!
Ektarr beat me to it but I was going to say you could check out gun broker See what the guns on there are going for. Probably give you a more real world idea of what the gun is going for verses book value.
Call a local gun shop also and see if they have a copy of the Blue Book of Gun Values. Sometimes the auction sites can be... well, let's just say people can be very proud of what they own. I checked gunsamerica a few months ago to see what people were selling their Swiss K31s for. You can still get one at the gun show for $180 in very good condition, but people were starting auctions for them at $300 - $500 in good to poor condition. A few people were still being in touch with reality, but not many. However, I know the gun shops around here will normally look a gun up for you in the blue book without a charge unless they are crazy busy.