223 Remington. The ... License to produce the AR-15 was acquired by Colt's Patent Fire Arms Manufacturing Co., Inc. The firm of Cooper-MacDonald, Inc., Baltimore, Md., was selected to promote ...

308 Winchester, the lower receiver and bolt-carrier design allow users to swap the upper receiver group for any Colt Mil-Spec upper chambered for 5.56 x 45 NATO (.223 Rem.). The Adapter Block ...