Requires the use of the .750 gas block or front sight base.Approximate Weight: 3lbs 3oz. SAM-R barrel with Service Match Heavy Contour BCMA(R) SS410 Barrels This BCM stripped barrel is machined from a 410 stainless steel. It features hand lapped button rifling with a 1/8 twist rate and M4 feedramps. To give the shooter the best accuracy this BCM SAM-R barrel has a service match heavy weight profile and a rifle length gas system. (410 stainless is a harder and more corrosion resistant than the conventional 416 stainless found in most barrels.) DLC Coating stands for diamond-lkike carbon coating, and is a nanocomposite coating that has unique properties of natural diamond low friction, high hardness, and high corrosion resistance. DLC PVD coatings advantages reduced coefficient of friction increased abrasive wear resistance anti-scuffing/anti-galling high fretting resistance high pitting resistance resistance to corrosion and hydrocarbon fuels high integrity of surface structure good adhesion to base materials DLC coatings directly improve wear resistance due to their high hardness, low coefficient of friction and high structural integrity. These coatings with thicknesses of only a few microns and with hardness up to 4000HV, result in increased firearm life and functionality. The DLC finishes, absorb oil and release it over time due to the unique characteristics. Requires the use of the .750 gas block.