Under federal law, unlicensed individuals can buy and sell firearms directly to one another without an FFL, provided both parties are residents of the same state. This is often referred to as a "private party transfer."

Certain categories of "guns" aren't legally considered "firearms" under the Gun Control Act, meaning they can often be shipped directly to your door without an FFL or background check. Federal Private Firearm Transfer Laws - USCCA

You buy the firearm online and select a local FFL dealer to receive it.

Many states, such as California, New York, and Washington , have passed "universal background check" laws that override the federal baseline, requiring even private sales to be processed through an FFL dealer. 2. Buying Online (The FFL Intermediary)