My father sold some guns and ammo through Amoskeag and his experience pretty much matched NTaxiarchis without the bidding war. Not a criticism of Amoskeag, just how things work.
When I disposed of my father's estate through a more local auction I ran into the same basic experience. In general an auction house is a good way to sell a gun or collection quickly, but you may not get what the guns are really worth. I really didn't have the space, time or inclination to bring all of my father's guns back home and spend a year or so trying to sell them for what they were really worth. I got about $35,000 for them and probably could have gotten maybe $45,000 if I had done it myself.