www.gunbroker.com probably the biggest around for a no-auction site check out: www.shootersexchange.com
www.auctionarms.com www.gunsamerica.com And FWIW, sale will STILL need to pass thru the hands of a FFL holder when crossing from one state to another. Most of my buys are Auction Arms, and some on Gunbroker. Shop carefully, READ description, LOOK at the feedback other customers have left for that seller. If selling, KNOW what you can ship, to who, and where.