The patent pending SMOOTHCAM(TM) system features a domed head, low friction cam pin and special upper receiver that offer ultra smooth operation. With its blended cam recess the UAR upper is machined from Billet 7075-T6 certified aluminum and milspec, Type3″ Class2″ Deep Black, Hardcoat Anodized. The UAR(TM) is a precision machined upper with a special proprietary bore that is ultra smooth with a roughness average in micro inches of 16″ as opposed to standard bored or milled uppers that are 32-63″ or higher. This reduces bolt carrier friction and creates a much smoother operation. Barrel nut threads, bore and barrel extension surfaces are all machined in one operation so that they are perfectly concentric and perpendicular to the barrel and fixing assembly. The cam pin recess has been carefully designed with a smooth surface that flows into the main reciprocation channel. This allows the specially designed radial, domed head cam pin to move with the minimum of wear against these internal surfaces.