Interesting how the laws differ in the various states.
Here in Oregon, if there are 25 or more guns for sale "on
the premises" it's a gun show, and background checks are
required on all sales, dealer or not, even in the parking lot.
Less than 25 guns? No check required. The range I belong to
has an annual buy/sell/swap get together for members. There
are never more than 24 guns for sale.