Richard Poplawski built a deadly arsenal in his Stanton Heights home that included at least one assault weapon. He might have done so legally. Under federal law, citizens may purchase long guns — including semiautomatic AK-47s — from other private owners without acquiring a license and without registering the weapons, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives. If a gun is purchased from a licensed gun dealer, a record of the sale... (GunPolicy.org)