An intermediate cartridge designed to outperform the .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 our 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), but barrels should still be headspaced and installed by a qualified gunsmith. 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.