Hammer Forged over a precision mandrel within .0001" and with bore tolerances held within .0002", this Swenson 1911 Barrel is a surefire way to upgrade or replace an old, worn out barrel. This barrel is manufactured from 4140 Steel, heat treated to 44 RC and features a polished bore with a surface finish of 16 microns or better. It incorporates a National Match Feed Ramp for more reliable feeding and function with diverse bullet profiles. This is a Semi Drop-In Barrel, and due to the vast selection and many different variations of 1911 slides and frames, minor fitting may be required. Outside Diameter measures .579" held to a tolerance of .001".