Whether you're building a new AR-15 or you need a spare bolt carrier group in your rifle bag. Here are 10 best AR15 BCG upgrades you can buy. We have over a decade of AR-15 experience to write this guide, and we have categorized them into budget, mid tier and high end options.
For the casual range goers, a budget BCG works. For serious shooters who burns through a ton of ammo, mid tier or high end options are recommended especially when shooting suppressed.
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Understanding 556 Bolt Carrier Group
The bolt carrier group is a vital component of your AR-15. It's primary job are:
- Locking
- Unlocking
- Extracting
- Ejecting
If the BCG is not well made, or fit the tolerance spec of the barrel it can cause many accuracy related issues or chambering issues.
Recoil and Felt Recoil: When a BCG is heavier, it can lessen both the actual recoil and the feeling of the recoil. The added weight makes the BCG move more slowly backward during the firing cycle, cutting down the recoil impulse. This makes the gun more pleasant to shoot, especially for long periods.
Cycling Rate: The BCG's weight can change how fast the gun cycles rounds. A heavier BCG usually slows down this rate, which is helpful when shooting with a suppressor.
Selecting The Best BCG
BCGs wear out because of the heat, friction, and pressure they face every time you fire your AR-15. By cleaning and taking care of your BCG, and choosing quality parts, you can stop most problems with your rifle and keep your BCG from wearing out too fast.
While most BCG on the market are MPI tested and the gas key is staked, but how can you differentiate among them?
A quality BCG with Parkerized or Phosphate coating will outperform a low-cost BCG that's priced higher due to a coating. This extra coating doesn't provide many benefits over standard options and may lead to more problems.
Gas Key
Choose a gas key that's chrome-lined and coated with phosphate. It should be constructed from 4130 or 4140 steel. After that, it's wise to hone the gas key's sealing surface to make it flat.
Use standard grade 8 Mil-Spec hex fasteners, or if available, Michigun OCKS gas key screws. The notches in these screws make them less likely to loosen during heavy use.
Apply a sealing compound to the mating surfaces as a secondary seal. This ensures a complete seal and good gas efficiency. Permatex or Loctite 620 bedding compound are the best choices for sealants.
Bolt
The bolt benefits from a hard, slick coating like NP3, Chrome, DLC, or Nitride. This coating helps in the bolt's locking and unlocking. Make the bolt from C158 steel, though 9310 is also acceptable if it comes from a reputable manufacturer with high quality control.
The ejector should have a beveled edge and be made from S7 tool steel. Sprinco ejector springs are recommended.
The extractor should be constructed from 4340 or S7 tool steel and coated with phosphate to help grip the case. Polishing the extractor's forward lip is a nice touch but not required.
Consider upgrading to Sprinco 5 coil extractor springs. If the barrel is under 14.5, use the insert and rubber O-ring from the Sprinco kit. If it's over 14.5, the insert alone is usually sufficient.
Bolt Carrier
For the carriers, 8620 steel is the standard. A chrome-lined bore is ideal, but not possible with Nitride coatings. If money is not an issue, go for an NP3 or chrome coating. If you're on a budget, the standard phosphate coating is effective. Full mass, M16 profile carriers are suggested for duty or defense guns.
Firing Pin, Cam Pin, and Gas Rings Choose a firing pin made of 8640 steel with chrome plating.
The cam pin should be made from 4340 steel and coated with Chrome, NP3, DLC, or Nitride to extend its life. Some companies offer dimpled cam pins for consistent wear and longer life.
AR15 BCG Budget Options
PSA Full Auto BCG
The Palmetto State Armory 556 BCG is a standout premium BCG, offered at a price that's truly competitive. Compatible with all other mil-spec AR-15 components, it undergoes strict quality control before being shipped to your door.
Designed to endure the intense force of full-auto fire, this BCG is a robust choice for your Semi-Auto AR-15. It's also a budget-friendly option; thanks to sales and price reductions from PSA, you can obtain what would normally be a $150+ BCG for less than half the price.
Made from Mil-spec Carpenter 158 steel, this BCG is built to accommodate heavier grain cartridges, such as subsonic .300 AAC Blackout ammo. Its phosphate outer lining and chrome inner lining provide heat resistance and lasting durability.
Despite its "full auto" tag, this BCG won't convert your semi-automatic rifle into a full-automatic one. It's simply designed to work with full-auto AR-15s and M16s, but it won't affect the function of semi-automatic guns.
Aero Precision BCG
The Aero PRO BCG is a new and cool addition to Aero's lineup. It's a step above the standard option, and it's worth the extra money.
- Carrier: 8620 material
- Bolt: 9310 material (C158 is preferred, but 9310 can be stronger if heat treated right)
- Extractor, Cam Pin, and Gas Key: 4140 material
Mid Tier BCG Options
BCM Bolt Carrier Group
The BCM is a simple option, and this is another similar choice with some improvements over the standard "Mil-Spec" bolt carrier group. This BCG comes with a C158 bolt, 4340 extractors, and an S7 tool steel ejector.
The gas key, made of 4130 steel, is chrome-lined and includes enhanced Sprinco extractor springs, a sealed gas key, and properly staked gas key screws. The carrier, crafted from 8620 steel, has a phosphate finish and a chrome-lined bore.
- Bolt: C158 material
- Extractor/Ejector: Tool steel
- Gas Key: Chrome-lined and properly staked
- Carrier: Phosphate with chrome-lined bore
Sons Of Liberty Gunworks BCG
SOLGWs has been making some headline news in the firearm world for making some very rock solid AR15s and the company puts a lot of attention on tight fitting parts. This BCG is another great option next to the BCM.
- Bolt: C158 material
- Extractors: 4340 material
- Ejector: S7 tool steel
- Gas Key: 4130 steel, chrome-lined
- Carrier: 8620 steel, phosphate finish with chrome-lined bore
2A Armament AR15 Regulated Bolt Carrier Group
If you're looking to invest in a top-tier AR15 BCG, consider the 2A Armament AR15 Regulated Bolt Carrier Group (RBC). This BCG is meticulously engineered, with excess material removed to lighten the weight and enhance performance.
Constructed from variations of 7075-T6, 8620, and 9310 heat-treated steel, the internals of this BCG guarantee durability. It's also coated with QPD nitride, providing excellent resistance to wear and corrosion. The adjustable titanium gas gate is a standout feature, allowing you to fine-tune the gas system on your AR-15 for peak performance. This option is particularly well-suited for suppressed shooting.
Toolcraft Left Handed 5.56 Nitride MPI Full-Auto Bolt Carrier Group
The Toolcraft Logo Nitride BCG is crafted from a carpenter 158 bolt and features a full-auto profile. It's designed for use in AR-15 and M-16 style rifles. To ensure uniform quality and reliable operation, the bolt undergoes magnetic particle inspection (MPI).
FailZero .300 Blackout BCG
The FailZero AR15 BCG is highly regarded for its durability, minimal friction, easy cleanup, and quality construction. It's coated with EXO Nickel Boron, which ensures a butter-smooth cycling action. This particular coating is celebrated for its hardness and lubricity, adding to the BCG's overall durability and smooth operation.
AR-15 enthusiasts value the FailZero bolt, constructed from MIL-SPEC Carpenter 158 steel, and the extractor, which employs a Viton O-ring to increase tension. The FailZero BCG also earns praise for its visual appeal, with some users admiring the contrast of the Nickel finish against a black rifle. With its mid-range price point, this product is an attractive option for those in search of a top-quality AR15 BCG.
Higher End AR15 BCGs
Sionics NP3 BCG
Nickel PTFE, also known as NP3, provides advantages over regular coatings. It enhances lubrication, increases resistance to corrosion, and simplifies cleaning. Unlike some less expensive Nickel Boron options, NP3 is thin and doesn't chip or crack easily. If you're interested in learning more, you can find a brief description on Sionics' website.
Sionics' bolt carrier groups feature an NP3 coated C158 bolt, equipped with a tool steel extractor and ejector. The bolt carrier group (BCG) also includes a Sprinco extractor spring and Optimized Carrier Key Screws (OCKS) to keep the gas key secure.
- Bolt: NP3 coated C158
- Extractor and Ejector: Tool steel
- Gas Key: Enhanced and secure
BRT Chrome BCG
This type of coating offers excellent protection against corrosion and adds improved lubricity, similar to NP3. Nowadays, Chrome BCGs are less common because they are costly to produce.
However, they remain a great choice for those seeking a coating that's superior to the standard phosphate. BRT's BCG features a Chrome C158 bolt and a full chrome gas key, all secured with properly staked fasteners.
- Bolt: Chrome C158
- Gas Key: Full chrome with properly staked fasteners
LMT Enhanced BCG
The LMT Enhanced BCG comes with a modified cam path, increasing dwell time to control suppressed or over-gassed systems. It features three gas ports, one more than the usual two, for improved gas flow. These ports are angled forward, directing extra gas away from the person using it. The carrier has special cuts on the bearing surfaces, helping it move through dirt and debris.
A special kind of steel, stronger than C158 and 9310, is used for the bolt. This, along with a changed bolt lug design, makes the bolt very strong. LMT uses a "lobster tail" extractor with two springs instead of one, making extraction more reliable and serving as a backup if one spring fails. LMT has also removed the lug opposite the extractor, balancing the load between the remaining bolt lugs.
- Cam Path: Altered to increase dwell time
- Gas Ports: Three instead of two, for better flow
- Bolt: Proprietary steel, super strong
- Extractor: "Lobster tail" design with two springs