An 80 lower receiver is a special type of aluminum alloy casting that is machined into the shape of a lower receiver for an AR-15 assault rifle. It enables receivers to be manufactured at home using only basic drilling and milling equipment, making them much cheaper than buying complete receivers from gun stores. Although most 80 lower receivers are completed without serial numbers or other identifying marks, they are still considered firearms by the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), and thus subject to all applicable laws and regulations.
80 lower receivers are often referred to as “ghost guns” because they can be bought and sold without any paper trail, making them attractive to criminals who want to avoid purchasing guns through licensed dealers.