GOA and other pro-2A groups are suing the Bureau of Alcohol Tobacco Firearms and Explosives. USA – -(AmmoLand.com)- On Thursday, federal agents raided the headquarters of Polymer80, one of the largest manufacturers of homemade firearm accessories. For years, Polymer80 has been producing “80% complete” lower receivers which the ATF determined to be incomplete and non-regulatable by the ATF as firearms. These receivers require holes to be drilled and surfaces filed before they become an actual, usable receiver, hence the term 80% receiver. You might have heard an anti-gunner refer to a completed homemade firearm as a “ghost gun” before.