Live auctions tend heavily to the "You got to be KIDDING!" side of things. Pawn shops CAN be a decent source.
On-line- Armslist, GunsAmerica, Gunbroker, and Auctionarms.
Storage auctions? No. Guns are a rarity, and the bozos from the TV show have convinced everyone there is 100 lbs of gold coins in that box of thermal underwear.
So what are you looking for?