AR-15, at first indication, is a deadly weapon and a second reminder; it is a modular gun platform that is infinitely able to accessorize and personalize. Besides its ease of use and adaptability to different shooting niches, an AR-15/M16 can be heavily modified, or even assembled from scratch by an average user.
The only thing you need to pay attention to is a few essential parts that endure most of the wear and have to be of excellent quality.
Along with a quality barrel, the Bolt Carrier Group (BCG) is another important rifle part, which needs to be built properly using suitable components right from the beginning.
Comparison of the Best M16 Bolt Carriers Groups
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What is a Bolt Carrier Group?
Most gun authorities would agree that the barrel with a bolt and carrier (or BCG) is the heart and soul of an AR-15 rifle. Many people compared the AR-15 action with a car engine since both utilize controlled explosion for functioning.
Designed to operate as the semi-automatic system, the AR-15 uses compressed gas from firing to move the bolt carrier group back, eject the empty brass, strip another round from the magazine, chamber it and reset the hammer, that is to say- cycle the “action”.
Physically, the upper receiver secures the barrel and houses the bolt carrier group. The BCG assembly consists of the carrier as the external housing for the bolt, gas key, firing pin, extractor, retaining pin and cam pin. Some shooters also count the charging handle in with this, but we will put it aside from BCG.
How to Choose an M16 Bolt Carrier Group
The AR-15/M16 was initially created to fit a specific set of needs requested by the U.S. Army, but today many owners use the AR-15 for home defense, hunting and range time. Any of these roles may require a number of customized parts for your AR rifle to function reliably.
In fact, upgraded BCG should provide increased reliability, durability and speed as well as improved action smoothness.
As for the BCG, you can either choose an entire pre-assembled bolt and carrier or purchase individual components to build your dream bolt carrier group. In both cases, you should have a basic understanding of bolt carrier groups that we'll explain in short words in this chapter.
Selecting a Bolt Carrier Group (BCG) for the intended purpose of your M16 can be a bit confusing with so many choices and types of material and coating available.
- First off, there are two basic bolt carrier configurations dubbed M-16 and AR-15. The M16 full auto bolt carrier groups have full mass at its tail while the AR-15 semi-auto BCG's have an extra cut that takes out some mass.
- Since the M16-style bolt carrier is heavier than AR-15 semi-auto BCG’s, it has a slower cycling rate, which may help your rifle cycle more smoothly. While this is a full-auto part initially designed for military full auto fire M16s, the standard M16 profile bolt carrier group is perfectly legal to own and use in your build.
- AR-15 bolt carrier groups come with one subcategory relatively new on the market. It is known as the Low-mass, or lightweight bolt carrier group, an extremely lightweight profile option that makes the rifle faster, smoother with an overall less felt recoil. This BCG type is built for “race guns,” the ultra-light competition rifles and it requires precision tuning and pairing with the adjustable gas block.
Other significant bits you should look for are the materials and coatings used in the construction of BCG, as well as the right quality inspections.
- The Mil-Spec finish called Parkerizing or phosphatizing is the most common method of protecting a steel surface.
- There are also more advanced nitride metal treatments known as Melonite and Tenifer, which are very hard and corrosion resistant.
- The newest one called nickel boron coating is nearly friction-free while it is a little smoother and stronger than nitride treating.
Besides steel as the most common material used for bolt carrier groups, you can also encounter aluminum and titanium BCGs. All of them have some advantages and disadvantages, but steel BCGs are durable, heat resistant, and withstand wear and tear while they are not too expensive.
- Every BCG component requires different types of steel, so the minimum steel quality for the bolt is considered the Carpenter 158 and 9310 steel.
- On the other hand, the carriers are often made from 8620 steel.
You should also look for the HPT or MPI marks printed on the bolt that means each bolt is individually tested at a proof load and examined for cracks or scratches in metal that the eye cannot see. HPT is short for the High Pressure Tested whereas MPI means Magnetic Particle Inspected and if you find them on BCG that confirms the part passed this type of testing after the manufacturing process.
Another term is “shot-peening”, which means that the bolt is relieved from the manufacturing stress during the process in which the bolt carrier is bombarded with tiny spherical shot pellets.
Review of the Best M16 Bolt Carriers
For this overview, we have selected only "full auto" or "M16" BCG since they are currently the most popular bolt carrier groups for building semi-auto AR-15. All of them are made of steel since this material is perfectly suitable for many AR-15 enthusiasts.
Otherwise, we have described BCGs with different types of finishes and coatings as these treatments also affect bolt carrier functioning and longevity.
Brownells - M16 5.56 Lightweight Bolt Carrier Group
The latest trend of the AR-15 platform is the lightweight bolt carrier groups, which can cut the weight of mil-spec bolt carrier group almost in half. One of the newest offerings comes with Brownells name on it and at 8.2 ounces; it weighs 3.4 ounces less than the standard BCG.
The model with mark CRC556LW010 has a nickel boron coating, which is definitely an upgrade from the nitride BCG. Except for the luxurious finish, this Brownells BCG is more resistant to corrosion whereas it offers an ultra-low coefficient of friction so that you can fire your AR-15 without as much lubrication. However, it may get some discoloration in the finish after repeated use
Brownells contender in the lightweight BCGs category is the silvery nickel boron finish bolt carrier group that ships completely assembled enabling a simple component swap without amateur gunsmithing work.
The Brownells M16 Lightweight carrier is made of 8620 tool steel and its housing a heavy-duty bolt machined of 9310 tool steel. The extractor is made of tool steel with Wolff spring, Viton O-ring and necessary black insert for high-temperature seals and chemical resistance.
At the end of the manufacturing process, the BCG is magnetic-particle inspected for any cracks, divots or scratches.
The Brownells M16 Lightweight Bolt Carrier Group is compatible with AR-15s chambered in 5.56 NATO, .223 Rem., 300 Blackout, and .204 Ruger
One note at the end; - to get the most out of your M16 Lightweight BCG, you should pair it with an adjustable gas block.
The Brownells is a top rated supplier of firearm accessories and gun parts, which usually has great self-branded stuff. The Brownells M16 Lightweight Bolt Carrier Group comes in three types, black nitride, bright gold titanium-nitride finish (TiN) and our nickel-boron.
Best for the Money:
Brownells - M16 5.56 Bolt Carrier Group Nitride Mp
Brownells is offering a whole range of AR platform connected products of decent quality that typically belong to the Best for the Money category.
Their M16 bolt carrier group is designed for use with either semi-auto AR-15 or the full-auto M16. The Brownells M16 5.56 bolt carrier group is fully assembled and includes a bolt, gas key, bolt carrier, cam pin, shrouded firing pin, and a retaining pin.
When we say Brownells M16 BCG meets all the criteria, it means that bolt and carrier are machined from proper steels to satisfy standard quality norms. The bolt in this assembly is made of 9310 steel instead of Carpenter 158, whereas the bolt carrier itself is fabricated from 8620 steel. Following machining, the process includes a heat-treated and shot-peened finish. The overall steel quality is assured with magnetic particle inspection with MP marking on the bolt.
Another selling point of Brownells M16 BCG is a nitride finish, which is an upgraded finish from mil-spec parkerizing. Nitride metal treatment is very smooth, corrosion resistant and much easier to clean than the old phosphate finish.
The Brownells Nitride M16 Bolt Carrier Group provides you whole BCG assembly where each element is finished in a black-nitride treatment that is not a plating/coating so it can’t chip, crack or peel. The only cons with this budget-friendly BCG might be some imperfections, like noticeable tool markings.
3. Daniel Defense - M16 5.56 Bolt Carrier Group
If you are looking for a branded mil-spec BCG, The Daniel Defense M16 5.56 bolt carrier group will provide you with strength and durability features for dependable service. This M16-style carrier features full-length shroud around firing pin, so this carrier may be installed on full-auto military rifles.
Like any military spec BCG at a premium price, DD's complete assembly with bolt, bolt carrier and other parts is ready to drop into the AR-15/M16 rifle or carbine upper of your choice.
As you would expect from a company with such a reputation, parts are made from the top materials. The bolt is built from Carpenter 158 steel and the carrier is made of 8620 carbon steel. The carrier bore and the gas key has been chrome lined and has properly staked gas keys. Complete bolt assembly has been heavy phosphate coated for excellent durability, and cycling with a variety of ammunition and during rapid semi-auto or full-auto fire.
The shot peened bolt offers reliable extraction, which is ensured with an extractor booster.
The DD's M16 Bolt Carriers are passed through the magnetic particle inspection and high-pressure testing to ensure they are free from imperfections that can lead to premature failure.
Daniel Defense complete Bolt and carrier assembly come in black Manganese Phosphate Finish per military specifications.
Although DD BCG's have a superior reputation for reliability and their workmanship is of the best quality, you can find some quality control issues with scratches and marring on the surface finish.
The Daniel Defense bolt carrier group assembly has an M16 profile that is full auto compatible and will work with semi or full auto rifles. As a benchmark in AR world, Daniel Defense comes with etched “DD” tactical logo on the side of the carrier visible through the ejection port.
4. Spikes Tactical - M16 5.56 Nickel Boron Bolt Carrier Group
Spike's Tactical is a US based AR manufacturer which produces a variety of quality AR-15 complete rifles, parts, and accessories but they are mainly distinguished by their bolt carrier groups made of steel for ultra high durability and backed by the Spikes Tactical lifetime warranty.
This complete bolt carrier group has an M16-type full-length shroud around firing pin and works in both .223/5.56 full-auto M16s and semi-auto AR-15s.
The Spike's Tactical BCG is built to Mil-spec standards, which mean that bolt is machined from Carpenter 158 steel alloy and carrier from 8620 carbon tool steel. As a downside, this all steel BCG is tipping the scales at 11.6 oz. making it heavier than their mil-spec counterparts do.
Carrier and gas key are hard-chromed inside and properly staked using grade 8 hardware. However, you can find a few complaints that the gas key was not properly staked and was loose
The extractor is also built of 8620 tool steel whereas its spring has been upgraded with a Viton O-ring and black extractor insert for increased tension and reliable cycling.
After machining this Spikes bolt/carrier set is High Pressure Tested (HPT) as well as Magnetic Particle Inspected (MPI) to detect any flaws and to ensure quality. The bolt is also shot peened for more extended durability and resistance to material fatigue and cracking.
As you read in the title, this is Nickel Boron Bolt Carrier Group with an excellent FailZero EXO nickel boron treatment which is more durable, eliminates friction, and is easier to clean. Besides silver finish for fancy factor, Spikes carrier comes with the spider logo engraved on the right side to add to the cool factor also.
5. Palmetto State Armory 5.56 Premium Full Auto Bolt Carrier Group
For AR-15/M16 building enthusiasts on a budget, the Palmetto State Armory bolt carrier group is the most affordable constructed following the military norms.
The PSA bolt carrier profile has typical M16 rear undercut for full-auto compatibility, making this BCG capable of firing full-auto.
On the one hand, it means the bolt is made of Mil-spec Carpenter 158 steel and the carrier is an AISI 8620 medium strength steel alloy, but on the flip side, their phosphate coating is a little bumpy and not very pleasing to the eye.
The carrier and gas key are machined out of bar stock. Both are chrome-lined on the inside, whereas the outside surface is a laser engraved manufacturer logo.
The bolt is shot-peened and stamped with HP and MPI markings that stand for High Pressure tested and Magnetic Particle Inspection.
This Mil-Spec bolt carrier group features a tool steel extractor that has O-ring inserts, but they are low quality and may become loose after short rounds stream.
While the gas key has been secured and lined with grade 8 hardened fasteners and staked per mil-spec, there are a few complaints about poor quality control, due to not properly staked gas key or some items that don't have the staking on the gas key.
Unlike the non-premium BCG that comes in almost a matte finish, the Palmetto State Armory premium BCG is polished, well made and slick. At 11.7oz, it is not the lightest one on the market and for sure, it is not recommended for a lightweight specialty build.
While some gun authors suggest the BCGs from PSA as a second choice, these mil-spec phosphate BCGs, though the cheapest in the whole article, still work reliably and do precisely what a bolt and carrier are supposed to do.
Types of BCG Coatings
Along with type and material used in bolt and carrier construction, there are many types of coatings for bolt carrier groups you can choose from. They range from phosphate coated bolt carrier groups useful for the most applications to the titanium nitride as the best overall bolt carrier group coating.
- As for the coatings, the standard parkerized Mil-Spec finish is durable and dependable and the most common coating you will find.
- However, many newer generation bolt carrier groups feature high-tech platings such as gold Titanium Nitride (TiN) and Black Nitride.
- The silver and shiny nickel boron (NiB) is also an advanced coating that has the extra advantage of being extremely corrosion resistant and requiring less lubricant.
If you are in the market for an M16 bolt carrier group, the easiest way to avoid some bad decisions is to check out articles like ours on choosing a solid and reliable BCG.
The bolt carrier group controls the small explosion close to your face, so we highly suggest you consider this assembly as one of the most important parts in your firearm and hence look only for the best, more durable BCGs from manufacturers who are widely regarded as the best and most reliable.
People Also Ask
For a long time, the AR-15 is a part of American culture but there are still many people confused with “gun experts” terminology that frequently mix the AR-15 names and types together without reason or explanation. For better understanding, the best way is to find an FAQ section in each article such as our “People Also Ask”.
Will an M16 Bolt Carrier Work in an AR-15?
Although the M16 bolt carrier is slightly longer and heavier with an additional lug at the rear of the bolt carrier group, it is fully compatible with an AR-15 semi-auto gun.
Even though an M16 style (aka Full-Auto) is designed for full-auto functioning in military rifles, these BCGs will perfectly work in an AR-15 but will not change your semi-auto AR-15 into a full-auto gun and it will have zero effect on how the rifle functions.
What is a Black Nitride BCG?
Black Nitride finished BCGs are adamant bolt carrier groups due to the applied process called ferritic nitrocarburizing (FNC). This finish is accomplished through the extremely high temperature where the nitrogen and carbon are diffused into ferrous materials.
Since the nitride bolt carrier groups do not require chrome lining, it is well-suited for both precision internal components such as the gas key or inner areas of the bolt carrier.
Even better, nitrided surfaces are very hard and have an attractive deep black finish.