18" SPR Profile AR15 Barrel. Made to true SPR Barrel specs by White Oak Armament, assembled using a stainless match grade blank in 1x7 twist rate. This barrel features M4 Feedramps, Wylde Chamber for reliability and accuracy with a wide range of ammunition, 1/2x28 muzzle threads. Rifle gas system, uses a 12" Gastube. .750 Gasblock seat, with dimple for gasblock setscrew.