A bolt carrier group, a.k.a BCG in short, is the heart of a rifle. A good bolt carrier ensures reliability in function and improves the overall accuracy and performance of the rifle.
Plus there are certain traits to look for when choosing a BCG for your AR-556. Here, we will learn about these traits and features that make a BCG worthwhile.
Additionally, we will also learn the difference between a full-auto and semi-auto BCG. To wrap things up, we will review the best BCGs available on the market for a Ruger AR-556 rifle. These upgrades certainly help you win your next competition.
Comparison Chart of the Best Ruger AR-556 Bolt Carrier Groups
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What is a Bolt Carrier Group?
A bolt carrier group, also known as the BCG, houses the components responsible for loading, ejecting, and firing a cartridge. It includes a bolt, the bolt head, firing pin, cam pin, gas key, and the metal casing(carrier), which houses all these components.
The gas key directs the gases produced in the chamber from burning gunpowder, back into the bolt carrier. These gases push the bolt backward as it ejects a round and a new round pops up from the magazine, which then cycles forward to load it into the chamber, using the bolt head.
The firing pin is embedded into the core of the BCG and hits the primer of the loaded cartridge to prompt the powder burn. The pin moves to and fro, along with the bolt, under the influence of the gases and the buffer spring. The cam pin keeps the bolt inside the carrier and the bolt and firing pin aligned.
Full-Auto vs. Semi-Auto Bolt Carrier Groups
The major difference between a full-auto and a semi-auto weapon is the bolt carrier and trigger mechanism. A full-auto bolt carrier has some extra material on the end. This rear lug pushes the sear release of the trigger mechanism downward, which allows for full-auto fire.
A full-auto bolt carrier group has extra material compared to the semi-auto, which makes it bulkier, but also more durable. Full-auto BCGs are designed to be more durable as they have to withstand more pressure compared to semi-auto carriers.
On the other hand, semi-auto bolt carriers provide a controlled and steady rate of fire. They allow you to keep track of the number of rounds fired and help with conserving ammunition. By removing full-auto capabilities, they remove any chance of a 'run-away' or slamfire.
Using a full-auto bolt carrier group is completely legal. That’s because a full-auto BCG alone doesn’t make your rifle fully automatic, but it does help with extending the service life of your rifle. Many people tend to use full-auto BCGs with their AR-15 rifles for this slight edge in reliability and get a different finish. A NiB finish for instance is much smoother, easier to clean, and adds a nice aesthetic since it is bright silver.
Features of our Favorite .556 Bolt Carrier Groups
Here are some of the features we think are a must have in a Bolt Carrier Group.
A good BCG must feature a drop-in installation design. Not to mention that it must already be complete with the firing pin. Such a BCG is easy to install and ensures that all parts have been properly put together and sealed in the factory by a skillful worker. A drop-in BCG can be easily switched out when needed.
Quality Material and Inspected
The quality of a BCG refers to two things - material and proper inspection. A BCG can either be made from steel, aluminum, or alloy composites. Each of them has its own properties and level of durability. Some people also go for lightweight, titanium BCGs for use in competitions. Different metals offer a specific mix of durability and performance. Additionally, a BCG must be properly inspected using best-in-class methods like MPI and HPT, to ensure they are good quality.
A BCG with a good finish is not only aesthetically pleasing, but also easy to maintain. High-grade finishes like TiN and Nitride-coatings ensure that there is minimal friction between the parts, so the bolt slides properly and quickly. Plus, BCGs with such high-grade finishes are easy to clean and maintain.
Staked Gas Key
Staking is a very subtle, but important, feature of a BCG. A properly staked gas key on the BCG ensures reliability and proper functionality under all sorts of conditions.
Forward Assist Compatibility
The AR-15 uses a direct impingement gas system, which might cause grime and fouling to build up if the rifle is not cleaned regularly. The forward assist was designed to push to bolt forward in such conditions. A BCG compatible with a forward assist has a pattern of grooves on its sides. Although, not necessary. But having a forward assist-compatible bolt does help. Plus, BCGs without forward assist are extremely rare.
Review of the Best Ruger AR-556 Bolt Carrier Groups
Based on the above-mentioned features, we have managed to handpick some of the best bolt carrier groups for the Ruger AR-556 on the market. These BCGs work exceptionally well on the grounds of quality, performance, and reliability. Additionally, all these BCGs are quite cost-effective and won’t burn a hole through your pocket.
Palmetto State Armory 5.56 Premium Full-Auto Bolt Carrier Group
This PSA bolt carrier group is the most economical and simple item on our list. The BCG has been made from carpenter 158 steel, which is the most common mil-spec material used for making such a part. The BCG has been chrome-lined on the inside and features a phosphate finish on the outside.
This mil-spec coating is in accordance with the military norms so the bolt might not look very pleasing to the eye. The metal of the bolt has been shot-peened, magnetic particle inspected, and high pressure tested, to ensure quality and durability.
The gas key has been secured using grade eight hardened fasteners and is staked per military specifications. The tool steel extractor has O-ring inserts to ensure proper cycling of rounds. The BCG is an exceptional combination of quality and price.
The best part of using this bolt carrier group is its full-auto compatibility. The BCG has a full-auto design, which ensures durability and reliability in the long run. Being full-auto compatible also means that the BCG can withstand a lot of stress compared to normal semi-auto BCGs. The BCG is good for normal uses with the AR-15 rifle, but not very ideal for competitions.
The BCG is full-auto compatible and is exceptionally inexpensive. Plus, it can be used for a wide range of applications. It has been designed as per military specifications so you can rest assured about the quality and performance.
Best for The Money:
WMD Guns - AR-15 5.56 Nickel Boron Bolt Carrier Groups
A semi-auto bolt carrier group from WMD guns with an impeccable finish and reduced weight. This BCG has been manufactured from high-grade steel alloy to strict military specifications.
The major point of attraction of this BCG is its Nickel Boron coating. This NiB-X is a self-lubricating finish which prevents any dirt or grime from filling up the carrier. It also means the BCG is easy to clean and has less friction between its parts. Cleaning just requires a simple lube and a quick wipe.
The package also includes a hammer, which can be replaced with the existing trigger assembly. The hammer features the same material and finish as the BCG, so compatibility between these two parts is just awesome. The bolt is shot-peened and MPI tested, so you can rest assured about its quality.
The gas key has been properly staked and all the components have been joined together firmly. The nickel boron coating is not only protective, but it also makes the BCG look more attractive. The right choice for competitive shooting and tactical applications
The WMD BCG features a self-lubricating nickel boron coating, which is impervious to corrosion and grime build. This is quite an impressive feature, which also justifies the price. The BCG is meant for competitive shooters.
3. J P Enterprises - AR-15 5.56 Full Mass Bolt Carrier Group
This BCG from JP enterprises features durable construction, since it has been made from 9310 stainless steel. The BCG is a full mass variant, which features the standard weight of the bolts used normally in duty rifles.
The 9310 steel ensures a longer service life due to its durability and resistance to breakdowns. The BCG features a 100% increase in bearing surface for better cycling and reduced wear on the inner surface of the receiver.
Unless you are looking to build a quick competition gun, this BCG is ideal for almost every other AR-15 application out there. The machining and finish are almost impeccable.
It is somewhat high on price, compared to the other bolt carrier groups in its category. But its quality, finish, and performance are worth every penny you pay for it.
The fit and finish of the BCG are amazing. This is also easy to clean, compared to phosphate finish carriers. The gas key is properly staked and every nook and cranny of the BCG has been machined to perfection.
The JP Enterprises BCG is a sturdy and flawless upgrade to your Ruger AR-556. This full mass carrier is good for almost every rifle purpose. The price of the BCG is too high, but it certainly matches the quality.
4. Double Star - AR-15 5.56 Bolt Carrier Group
Looking for a quality BCG for back-up use? This bolt carrier group from Double Star is your answer. It has been designed from 8620 carbon steel for strength and durability, not to mention the proper balance between weight and equilibrium.
This also features a Parkerized mil-spec finish, which can be cleaned easily with the help of a rag and some lube. The product has been designed to standard specifications, so it serves as a normal replacement or backup to your existing bolt carrier group.
The BCG is MPI which also assures you about its quality. It is easy to install and works with many guns. This product also includes a hard-chrome plated steel firing pin and is chrome-lined on the inside for longer service life.
The gas key has been properly staked, so it is not just another basic, low-quality BCG for your Ruger AR-556.
The Double Star BCG ought to be seen as a replacement or backup for the normal AR-556 BCG. It is inexpensive and made from the most common materials, so it will give you the feel and performance just like the factory BCG
5. Brownells - M16 5.56 Lightweight Bolt Carrier Group
This is by far the most innovative, effective, and aesthetically pleasing bolt carrier on our list. Brownells M16 Lightweight Bolt Carrier Group features a heavy-duty bolt made using 9310 tool steel and is machined of 8620 tool steel.
This features a minimalistic approach towards design, meanwhile keeping the strength and durability of the system intact, and even enhanced. Most of the mass from the carrier has been reduced by removing the extra metal.
This makes the BCG extremely lightweight in comparison to its counterparts. The reduction in weight also allows the felt recoil of the weapon to be reduced, making this BCG ideal for competitions and precision shooting.
The bolt carrier group is available in nickel-boron, titanium nitride, and simple nitride finishes, all of which are exceptionally pleasing, easy to clean, and have low friction among their parts.
The BCG weighs only 8.2 ounces and is compatible with AR-556s chambered in multiple calibers including 5.56 NATO, .223 REM, .300 Blackout, and .204 Ruger.
The Brownell's BCGs in different finishes have been designed for competitive and precision shooting. Their finish is just splendid and so is their durability and performance. The best part is the right and fair pricing, which is unbelievable, compared to the similar BCGs on the market.
The bolt carrier of a Ruger AR-556, or of any rifle, is comprised of several basic parts. These include the bolt, carrier, gas key, firing pin, and cam pin. The BCG is responsible for loading, firing, and ejecting each cartridge. A good BCG must be sturdy, reliable, have a good finish, be easy to install, have a staked gas key, and compatible with forward assist for optimal function. Heavy full-auto BCGs are good for long service life and durability, whereas lightweight BCGs are good for reducing the recoil.