| YHM 6.8mm Barrel 16 In Fluted - No Chrome - YHM-80-TF-NC Chambered in 6.8mm SPC II, with a 1:10” 6 groove twist. These barrels feature M4 style feed ramps for reliable function. Threaded models have a 1/2”-36 thread. 4140 steel, heat treated to RC 25-32. Our barrels are designed to fit a 0.750" gas block |