The Bear Creek Arsenal Complete M16 Bolt Carrier Group is a quality part for your next build. The full mass M16 pattern 8620 steel bolt carrier has been treated with a super slick salt bath nitride finish for easy cleaning, reduced friction, and a reduced need for lubrication. The 9310 steel 5.56 NATO pattern bolt assembly has a durable manganese phosphate finish. A properly staked gas key and forward assist serrations round out the great features. To top it off, each BCA bolt carrier group is magnetic particle inspected to give you peace of mind that your carrier group is from from material defects.