There may be the legal matter of selling that many in one year with the ATFE. Auction sounds like a good idea to me. I'll bid $450! Okay $650!!
On individual sales? There used to be a limit per year. If you made a profit you bet your ass you will need to be an FFL, or it will have to be processed through an FFL. I believe this is for ONE SALE. They recently changed the law and tightened it up.Selling off a gun collection does not create legal issues, now if you took that profit and built back a collection that big in short order you could get on the radar