The USP was developed at the same time as the SOCOM MK23, the pistol underwent much of the same testing. The barrel is cold-forged from chromium steel for increased life. USP barrels after November 1994 use a polygonal profile; 1994 and earlier models use traditional 'land and grooves' rifling. During testing, a bullet was deliberately lodged in a USP barrel. Another cartridge was then fired into the obstructing bullet. The second bullet cleared the barrel, resulting in a barely-noticeable bulge. The pistol was then fired for accuracy, and the resulting group measured less than 4 inches at 25 meters.