How many guns are we talking about? If there is a significant number, +20 or so, you my look into Durys. They are in Texas. They pay 70% of fair market value. Call them up. If they think it will work, they will send you a box/crate and you ship it to them at their cost. They send you payment after that.
https://www.durysguns.com/sell-your-guns/
https://www.durysguns.com/sell-your-guns/