US Patent 9638484 Rifle apparatus, system, assembly, and method

A rifle apparatus and method wherein the rifle includes a replaceable, threaded, adjustable barrel assembly which is configured for quickly changing the barrel length of the rifle, converting the rifle for using a different caliber of ammunition, and/or accurately determining and quickly setting the headspace in the firing chamber of the weapon for firing the new ammunition. Further, the rifle apparatus preferably also includes a replaceable lower receiver with a well opening and a corresponding magazine retention and release assembly for receiving a magazine clip for the caliber of ammunition fired by the replaceable barrel.