The below link will take you to the Pooshka.com web site where they have the sale and trade values (good to fair) of most all major brands and models of firearms.  They also have a sale/auction section.  They seem to be correct/realistic on their values, but remember it is just a guide.  Some firearms will be higher on the market due to rarity or demand.  Please note that you need to read their model charts from left to right in order not to overlook the specific one you are looking for.

 

http://www.pooshka.com/

Directory