Blue Book is no longer the price guide it was intended to be although it is a very valuable resource of firearms information. Dates of MFG, firearm configurations and specs etc. Regarding pricing on USED firearms, as many have mentioned, use the real time resources available to us via internet, gun shows, gun stores, Gunbroker etc. To further complicate the firearms pricing challenges we face, add regional influences as well as provenance. Experience is our most valuable resource and the longer you have been buying, selling and trading guns the better you are at accurate valuations.