Helix 6 Precision Carbon Fiber 308 Winchester AR Rifle Barrel - 20in - Helix 6 Precision's carbon fiber AR barrels come complete with barrel extensions. Simply install, headspace, and head to the range. Our AR barrels use hand lead lapped button rifled 416R stainless steel cores for outstanding accuracy and durability. Barrels feature a stainless pre-drilled section for optimal gas tube length based on caliber and finished barrel length. Wrapped in carbon fiber using our proprietary process, Helix 6 AR barrels are significantly lighter and manage heat better than traditional barrels, enhancing your performance and the life of the barrel. Threaded Barrel: 5/8 x 24