I live in Colorado and depending on what you have and how many guns you have can be challenging to sell here in this state. Mark Reynolds used to be the go-to gun shop for these type guns, but he closed his shop earlier this year. The next best option for someone knowledgeable to talk with is Brian Williamson at Mountain guns in Conifer Colorado. Brain has a nice high-end shop along with him being very experienced.
https://www.mountaingunsltd.com/
Another thing to consider if you try to consign them locally is how the gun selling game has changed here in the last few years. All gun sales within the state "even private person to person" now require a federal background check with a fee for doing them done by a dealer with a three-day waiting period before the buyer can take possession of the gun. Then we also have a newly enacted 6.5% excise tax on all gun sales which is on top of the normal sales taxes.
In short, what I'm trying to say is depending on what you have, contacting Josh as mentioned by others would be a good starting point and I have sold guns through LSB auctions as well, but if it were me, I'd start with Josh or Brian and go from there.
Also be aware that if you sell directly to a dealer that more than likely the offer for them will be somewhere between 50-60% of the value of the gun. They have to make money on them and that's just the way the game is played.