Palmetto State Armory 18 CHF stainless special profile barrel with gas block tube middy 200 rounds plus or minus down the tube. With flash hider. This barrel uses 6.8 or 224 Valkyrie bolts, mags. The 6.8 is a better choice for hunting deer hogs with its increased energy. In my opinion the 6.8 feeds better, runs better than the Grendel I do shoot both rounds.