[Centurion2000]

One question for both gentlemen: how many "trunkloads" of firearms - nice imagery - can someone legally sell in a given space of time before he is required to have an FFL? I know the answer, and I suspect they do too, but I don't see it mentioned... one can only speculate as to why.

So what is the answer for that question ?

[Indrid Cold]

According to the book "Unintended Consequences", it can be as few as one gun. If you buy a gun at a gun show, an undercover ATF agent may come up and offer you waaaay too much money for it. If you sell it, you go to the pokey, as now you're not "adding to your collection", or "selling from your collection", but engaging in gun-dealing without a license. Or that's ATF's take, anyway.