From Fox San Diego:

Karras said the ATF threatened to shutter their business if they didn’t hand over the names of 5,000 customers who have purchased an 80 percent lower receiver (the base) for building an AR-15.

It is legal to build a rifle from scratch without serial numbers only if the base is manufactured to ATF specifications. The base is not considered a firearm if it’s sold separately.

A manufacturer made an 80 percent receiver in plastic with a different material and colors which show exactly where the customer can drill making it easier and cheaper to build. The ATF said it is illegal.

Full story and more details at the link. I’m not sure he’s going to win this one, not with Obama’s entire government running rough-shod over the U.S. population and the Constitution.