I have experience in disposing of two collections. First was a few years ago when Cousin wiped out in a private plane.
I went the auction route with farm equipment, household and personal items, and his military surplus collection. We auctioned a few guns with the household items. The auctions netted more than expected as lots. Some individual items sold lower than expected and others sold for more than we thought.
Not only was he a collector, he was licensed ( no store front) and bought and sold lots of items. Fortunately his inventory was low. His collection was basically Smiths, Colts, Winchesters, and Brownings. He liked to have his personal favorites engraved.
I can tell you that engraved Smiths went fast, as did most of the Brownings and Winchesters. There is not a buyer for a fully factory engraved, ivory stocked matched pair, for example, every where you look. I was almost two years dispersing all his embellished revolvers and longer on one embellished rifle.
I sold a lot of the collection through a large dealer at 10% commission and I set the prices. There is a large spread in what different dealers wanted - up to 40% - no thanks. I charged the heirs nothing.
I find myself getting older with way too many guns. Most will bring good money rather quickly. I plan to gift several. One S-I-L, knows the business and can disperse the remainder quickly. I only have a half dozen or so that will be priced beyond the average Joe.
The second was for a widow. Her deceased husband left about forty guns. I visited with several dealers as to values and gave her an expected sell price and an optimistic sell price. (I was not a buyer). An individual came along and bought them all at the upper price. Under retail, better than dealer. Good for her.
I would sell some now, but my wife is strongly opposed. She says that our guns are much better than money in the bank at today's meager interest rates. I think she is correct.
Jack