In gun stores, there's only three places they make money: 1) used guns, 2) accessories, 3) services, like smithing and training.
Unless you're desperate, do not ever sell a gun to a gun shop or pawn shop. Because only a fool of a business owner would pay you more than 50-55% of the value of that gun, that will need to sit on their shelves and lock up working capital until it is sold. That's their target percentage, virtually always - and those who don't follow that rule usually end up going out of business.
As others have noted, gunbroker and some other places online are a much better opportunity for getting the most out of your guns. You might as well post on here too, since you're Classifieds Approved.