This Bear Creek Arsenal AR-15 16" M4 profile, parkerized Chrome Lined 5.56 NATO barrel has a mid-length gas system with a 1:7 twist. Our AR-15 parkerized rifle barrels are made from the finest 4150 Chrome Moly Vanadium and precisely rifled for high accuracy at a great price. Use a Bear Creek Arsenal ar barrel in your AR15 next build and experience superior performance back by a lifetime warranty!