Well, whatever you'll call it, it's a pretty big loophole:
http://money.cnn.com/video/news/2016/01/11/gun-show-loophole-explained.cnnmoney/index.html?iid=hp-stack-dom
http://money.cnn.com/video/news/2016/01/11/gun-show-loophole-explained.cnnmoney/index.html?iid=hp-stack-dom