So there are a few auctions around the area in the upcoming weeks that im planning on going to and i really cant find anything with the rules for buying guns at auctions in MN.  So if anyone has any experience with them im guessing since im over 18 i can buy a long rifle but not a hand gun correct?  Also the rule that an 18yr old or more can buy a pistol from a private seller does that work in MN also on not?  Thanks for the help guys...  Also anyone round Willmar that wants to shoot sometime get ahold of me on here and we can go shoosting...

You still cannot by a Pistol at an auction at 18-20 must be over 21.

Same as if you walked in and bought from a store.

Perhaps one of our moderators can tack a link to the ATF FAQ?  As once again, it has the most complete answer.

K. AUCTIONEERS (K1) Does an auctioneer who is involved in firearms sales need a dealer's license? [Back] Generally speaking, there are two types of auctions: estate-type auctions and consignment auctions. In estate-type auctions, the articles to be auctioned (including firearms) are being sold by the executor of the estate of an individual. The firearms belong to and are possessed by the executor. The firearms are controlled by the estate, and the sales of firearms are being made by the estate. The auctioneer is acting as an agent of the executor and assisting the executor in finding buyers for the firearms. In these cases, the auctioneer does not meet the definition of engaging in business as a dealer in firearms and would not need a license. An auctioneer who does have a license may perform this function away from his or her licensed premises. In consignment-type auctions, an auctioneer often takes possession of firearms in advance of the auction. These firearms are generally inventoried, evaluated, and tagged for identification. The firearms belong to individuals who have entered into a consignment agreement with the auctioneer giving that auctioneer authority to sell the firearms. The auctioneer therefore has possession and control of the firearms. Under these circumstances, an auctioneer would generally need a license. If you are not sure if a license is needed in a particular consignment auction situation, contact your local ATF office. See ATF Ruling 96-2. (K2) If a licensed auctioneer is making sales of firearms, where may those sales be made? [Back] In a consignment auction, firearms may be displayed at an auction site away from the auctioneer’s licensed premises and sales of the firearms can be agreed upon at that location, but delivery may only be made to purchasers after the firearms have been returned to the auctioneer’s licensed premises. The simultaneous sale and delivery of the auctioned firearms away from the licensed premises would violate the law, i.e., engaging in business at an unlicensed location. However, if the auctioneer is assisting an estate in disposing of firearms, the estate is the seller of the firearms and the estate is in control and possession of the firearms. In this situation, the firearms may be delivered from the auction site. See also Question K1 and ATF Ruling 96-2

So I would interpret all that to mean that if it's an estate auction, you would only need to be 18.  If it's a consignment auction, you'd need to be 21.

Why not just call the auction house and ask them if they will sell to you?