Im looking to build an AR pistol and I was wondering if I bought this lower http://www.shop.countrysidewalk.com/Superior-Arms-AR15-Complete-Lower-Receiver-without-stock-AR15BLT-SU.htm;jsessionid=09248208FD2692F9AA3DAD8FC4FA7C21.qscstrfrnt01 could I legally use it to make a pistol? I basically...