The Sons of Liberty Gun Works SPR Barrels are optimized for accuracy. The SPR contour and 5/8x24 threads at the muzzle are by no means lightweight, but they are routinely shooting 1/2MOA groups with multiple types of ammo. The PRECISION series is 416R stainless steel, black oxide coated, and cut with .223Wylde chambers. These barrels are also polygonal rifled with a 3 groove, 1:7 twist bore. Features5/8x24 Threaded Muzzle.750"Gas Block JournalBlack Oxide Finish3 Groove Polygonal Rifling