My father was a gun collector and when he passed away all his firearms were documented and he had estimated values on each. The values were under estimated as he did the estimates several years prior to his death. One other thing he did that hasn't been mentioned was that he had another FFL (Federal Firearms License) holder whom he trusted lined up to handle the sale of his pieces. This was truely invaluable as this was prior to the internet and for a member of the family to get the pieces out there would have been extremely difficult and my mother would have never received close to their value.

If you know and trust someone in the field it would be a real relief to your family to have someone set up to handle the sale. A fee or percentage of the sale could be alloted to the individual handling the sale. In many cases the seller would probably prefer to have a piece or at least dibs on a piece of the collection.