By the very nature of publishing it will always be months if not a few years behind the actual value. It takes months to put together the information, check the numbers, edit and then print a book. Just look what happened with Colt snake guns like the Python a few years ago. Values can really take off so in very short period guns can double, triple, quadruple i weeks and months. When a book went to press it can already be way off when a run on something takes place.
Next you need to understand how many of the values are generated. Most of the new production firearms it appears are just straight-line depreciated from the normal list price. That also seems to be how they come up with prices on a lot of collectables. Reality is guns depreciate on a curve as condition drops. Often that curve can be pretty darn steep when a gun drops below 80% or 90%.
My understanding is they don't really go out and look at the actual market for each and every firearm listed. There just isn't time.
On more specialized collectables say like Colt SAA, older Winchesters, shotguns like Parker and Foxes, etc., I've heard they contact collectors and experts in those firearms to help with values...(okay I can see that some of those top collectors may have a conflict of interest when it comes to giving values of what they collect but that is just me) On much of that stuff the top values are as far out of whack from reality as are the 10% prices.
I look at the Blue Book as a place to start when valuing a gun. I find recently closed auctions a much better guide when it comes to hitting an actual "today's" value.
Okay that was my ramble for the day...forgive typos and missed words.
