Criterion Barrels AR-15 Barrel HBAR Contour 6.5 Grendel 22 inch Mid Length 1-8 Twist 5/8x24 Thread Stainless Steel Finish Black. 223 Remington and 5.56 NATO at longer ranges the 6.5 Grendel has increased in popularity as an alternative chamber option for the AR-15. Criterion is now offering a selection of 6.5 Grendel AR-15 barrels profiled in Their popular Hybrid and HBAR contours. These configurations offer a range of barrel profiles and lengths. Chambers are finished to accommodate Type II bolts (with a .136 recess). Each barrel comes with a proprietary barrel extension incorporating a finer thread pitch to allow for greater chamber wall thickness to accommodate the 6.5 Grendel's higher pressure for added reliability and safety. Specifications for Criterion Barrels AR-15 HBAR Contour 6.5 Grendel Barrel: Manufacturer: Criterion Barrels Color: Black Fabric/Material: 416R Stainless Steel Caliber: 6.5mm Grendel Barrel Length: 22 in Barrel Profile: HBAR Gas System Length: Rifle Length Threads per Inch: 5/8x24 Barrel Twist Rate: 1-8 Flutes: No Gun Make: AR Platform Gun Model: AR-15 Features of Criterion Barrels AR-15 HBAR Contour 6.5 Grendel Barrel Contour Hybrid HBAR Gas System Length Rifle Length Mid-Length Material and Finish 416R Stainless Steel Chamber 6.5 Grendel Twist 1-8 RH Gas Block Diameter .750 Muzzle Thread 5/8 x 24 .630 Package Contents: Criterion Barrels AR-15 HBAR Contour 6.5 Grendel Barrel What firearm models does the manufacturer say Criterion Barrels AR-15 HBAR Contour 6.5 Grendel Barrel is compatible with? The manufacturer says that Criterion Barrels AR-15 HBAR Contour 6.5 Grendel Barrel is compatible with AR-15Criterion Barrels 65G22S-HB12: AR-15 Barrel HBAR Contour 6.5 Grendel 22 inch Mid Length 1-8 Twist 5/8x24 Thread Stainless Steel Finish Black