Stern Defense Barrel Features The Stern Defense Barrel is machined from 4150 chrome moly steel a material widely trusted in the AR platform world for its strength and resistance to heat under repeated firing. At 16.1 inches in length the barrel meets standard rifle length requirements while delivering good velocity out of a .45 ACP pistol caliber carbine build. A 1:16 twist rate is matched to common .45 ACP bullet weights stabilizing projectiles for consistent accuracy downrange. The barrel ships threaded 578x28 accepting standard .45 caliber muzzle devices without additional machining. A black Melonite coating is applied to protect the barrel from corrosion and wear extending its service life even under hard use. This coating also reduces friction during cycling helping keep the action running smoothly shot after shot. Builders should note that .45 ACP uppers using this barrel require an enlarged ejection port and an 11 ounce buffer or heavier is recommended when paired with a carbine spring. Made in the USA to demanding tolerances the Stern Defense Barrel is a dependable choice for .45 ACP carbine builds available for sale at GrabAGun. Stern Defense Barrel Specifications Manufacturer: Stern Defense Caliber: .45 ACP Length: 16.1 Material: 4150 Chrome Moly Steel Finish: Black Melonite Twist Rate: 1:16 Thread Pattern: .578x28 Made In: USA Barrel Length: 16.1 Available At: GrabAGun