Helix 6 Precision Carbon Fiber 6.5 Grendel Rifle Barrel - Helix 6 Precision's carbon fiber AR barrels come complete with barrel extensions. Simply install, headspace, and head to the range. Helix 6 Precision's 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. Has 5/8 x 24 muzzle threading.