If you're selling within 30 days of buyingapparently if only affects you if you're making a profit. I sell all m ine at a loss.
If you're selling an unused new condition firearm
If you're selling multiple of the same firearm over a 'period of time' that they determine is too fast
If you sell over an arbitrary number of firearms in an arbitrary period of time
It affects many of us. They leave it vague to try to include as much as they want to. This is not a small rule.