Gun show laws

[Skans]

if you sell a firearm to a private person, you hang on to it till the new buyer gets his license, or if you do it through a dealer, the dealer takes possession.

This is similar (not exactly the same) that we do with transfers of full-auto machineguns, silencers, and a few other types of NFA regulated guns. Most states here in the US (exceptions: some of the northeastern states, northern-midwestern states and California) are as I described earlier - not much red tape involved in buying or selling a gun.