AR BCG Melonite vs Nickel Boron (NIB)

Choosing your AR Bolt Carrier Group

The Bolt Carrier Group is the heart of the AR. It is comprised of a bolt carrier, bolt, extractor, extractor spring, gas rings, gas key, firing pin, firing pin retainer and cam pin.

Bolt Carrier

The AR-15 bolt carrier comes in two different configurations, M16 and Commercial. The M16 or full auto bolt of course was designed for the abuse of full auto and select fire weapons. Current mil specs state that the bolt carrier to be made of 8620 Steel, chrome lined and mag phosphate finished. The commercial market has many upgraded coating you may want to consider. This will be covered below.

The Commercial bolt (AR-15) was designed to eliminate the features of the M16 it also provides a lighter weight. This was popular after the 1994 assault weapons ban and you will still see the big manufacturers utilizing these especially in their entry level guns. Also in the commercial market is the competition world where you will find specialty manufacturers making very lightweight bolts.

The weight of the bolt will change the recoil and will adjust your timing and tuning of your gas system. The lighter the bolt the more you will have to deal with being over gassed and an adjustable gas block will become a requirement for the lightest weight bolts.


The bolt will need to be matched with the caliber you are choosing for your AR Build. Some calibers such as 5.56 / 223 and 300 Blackout are interchangeable. There is a big debate on what material should be used in manufacturing Carpenter 158 and 9310. Current mil-spec dictates Carpenter 158 however there were posting that there were recommendations that this be changed to 9310. The paperwork for that recommendation could not be produced. Depending on which Kool aid you want to drink different manufacturers have posted data supporting the claims of why theirs is the best. The bolt houses the extractor, extractor spring and your gas rings. These parts wear and will need to be inspected and replaced on a periodic basis.

Gas Key

The Gas Key mates with the gas tube. Mil-spec dictates these should be chrome lined, utilize grade 8 screws and staked in place. If improperly installed or excessive wear you will have a gas leak and will leave your AR inoperable.

Firing Pin

The firing pin is generally made out of steel and is typically chromed. The finish will vary between a matte and polished depending on the supplier. You will also find titanium pins which will be lighter and state the properties of better resilience with the higher heat and cold temperatures.

Mag phosphate vs Nitride and Nickel Boron

Mag phosphate is mil-spec and the diehards will swear by them. Mag phosphate works there is no doubt about that it resists corrosion and is very durable, however it loves to hold on to carbon and provides no lubricity. For these to run reliably you must keep them well lubricated. You will hear the old stories of just dip in some 10w-40w shake it off and go to work. While I am sure this has worked for some it is not advisable. While it is recommended to run this type of bolt wet (meaning well lubricated) it can be too wet and cause just as many problems as running your bolt dry. There are lots of lubricates choose what you like best.

Nitride retains the properties of corrosion resistance, is extremely durable and has self-lubricating properties. It will make cleaning easier due to less carbon build up. It will still need lubrication but not near as much and will run longer in between maintenance.

Nickel Boron (NIB) has proven to be the best friend of those that want the fastest clean up and may be not the best at regularly maintaining their firearm. Being a bright polished nickel brings different reactions, some just prefer the properties, while other purchase because it adds a different look and others will choose to go to the nitride because they don’t want a way for it to reflect.