Best BCG For A 300 Blackout: Quality Bolt Carrier Group Reviews

AR-15 platforms provide an incredibly HUGE array of options to customize your rifle and personalize your shooting experience. Built upon this foundation, the 300 Blackout allows for a great range of various caliber options, and is designed to handle both subsonic and supersonic rounds. This means you need to have a basic understanding of how your gas system works to power your ammunition in the most accurate, and efficient manner. 

The Bolt Carrier Group, better referred to as the BCG, is the heart of your rifle and works as the main part of your gas system and is responsible for semi automatic function. However, there are tons of choices you can pick from, so we’ve highlighted some of the most popular tried and true BCG options to save you from having to sift through them all on your own.

Here’s A Quick Look of Our 5 Best BCG For A 300 Blackout

The Bolt Carrier Group Defined

Bolt carrier group for an AR-15 at an angle with brown behind and shadow

The BCG is the part of your rifle or pistol gas system responsible for semiautomatic fire. It works in the following manner:

  • First, it allows the firing pin to strike the primer on the chambered round.
  • Second, it grabs and ejects the spent shell casing.
  • Third, it re-cocks the hammer in the lower receiver to receive the next round.
  • Forth, it grabs a new round from the magazine and chambers it.

That is a LOT going on, and it all happens in about the space of time it takes to pull the trigger (or, less than a second). Accurate, quick firing of your weapon is dependent on the performance of the BCG, so choosing a part that is dependable and accurate is incredibly important. 

This all works because of the gas carrier that forces gas into the body of the BCG, forcing the bolt to ‘unlock’ and drive backwards into the buffer tube to compress the buffer and buffer spring. The decompression of the spring drives the BCG back into the upper receiver to eject the spent casing and ready the next round. The bolt also ‘relocks’ into place until you pull the trigger again. 

BCG Parts And What They Do

To further explain the complexity of this process, let’s explore the individual parts of the Bolt Carrier Group. Each has an important job to do, and works together to make a complete BCG system. 

Bolt Carrier

The bolt carrier is the housing of the entire BCG and contains ALL the other parts. This part is what contacts the buffer spring and absorbs the incredible force of expanded gas. The strength of this part is crucial for not only proper use, but safety, and is made from three types of forged steel: Carpenter no. 158, 8620, or 9310. 

Gas / Carrier Key

The gas, or carrier key, protrudes from the top of the bolt carrier and helps harness the gas from the gas tube onto the body of the bolt carrier. This is an important part as it controls the locking and unlocking of the bolt. 

Bolt and Extractor

The rotating bolt, as explained above, unlocks under pressure. There is a cog like ‘star’ on the front of the bolt which works with the extractor to allow the grabbing of each spent round for extraction. As it rides back forward with the movement of the buffer assembly it allows the bolt head and extractor to grab the next live round. 

Bolt Gas Rings

Small gas rings on the bolt trap the expansion of gas within the bolt carrier. This allows the pressure to build for the operation of the bolt rather than it simply dispersing. 

Firing and Retaining Pins

The firing pin rests in the bolt and protrudes just slightly from the head, next to the ejector. When the trigger is pulled and the hammer releases, the hammer hits the back of the pin. Then the pin then comes in contact with the primer to fire the round. The pin must move freely, but without the retaining pin, would fall out. The retaining pin keeps the firing pin from slipping out of the bolt. 

Cam Pin

Cam pins are used to help keep things where they belong, and in this case it works to prevent the bolt from rotating too far when it unlocks. It works to keep the bolt and firing pin rotating and moving as one unit.

Full Auto VS Commercial VS Mil-Spec Terminology

300 Blackout Bolt Carrier Group

A full-auto, or M16 BCG, WILL NOT transform your weapon into a full-automatic option. It also IS NOT illegal to purchase or require any special permissions. In fact, it is barely any different than a commercial, or semi-auto, option. The only difference is a thicker end to allow use of the auto sear, or a component that locks and unlock the bolt continuously when you keep the trigger depressed in a full-auto configuration. Since you don’t have a full-auto configuration, it works the same as a commercial BCG.

You also probably hear the term Mil-Spec thrown around. If you don’t know what this mean, you are new to the world of weapon builds, but that’s okay because we all have to learn sometime. Mil-Spec is actually exactly how it sounds: it refers to the part, or weapon, having been built to pass military inspection. Many parts used in a BCG are considered Mil-Spec, providing you the peace of mind pertaining to quality and durability. But for the entire BCG to be Mil-Spec,  it must include the following:

  • Carpenter No. 158 Steel Bolts
  • Interior Chrome plating
  • Shot peening
  • Grade 8 fasteners

Materials and Strength

As mentioned earlier, the BCG is made from one of 3 different steels. These materials are graded based on both tensile and yield strength. Tensile strength is defined by the maximum stress an object can withstand without stretching. Yield strength measures how much force must be exerted on something before it permanently deforms.

Carpenter No. 158 Bolt Steel

This is a Mil-Spec steel for bolt fabrication and has amazing performance and durability. It is a case hardened steel to prevent cracking and surface wear. 

  • Tensile Strength: 1103 MPa
  • Yield Strength: 931 MPa

9310 Steel

This steel is more readily available than the Carpenter No. 158 and is used for both carrier and bolt manufacturing, but isn’t inferior in strength or durability. Less expensive, it helps influence quality parts at a more affordable price. 

  • Tensile Strength: 910 MPa
  • Yield Strength: 570 MPa

8620 Steel

The 8620 Steel is a Mil-Spec option for carriers. It is affordable and of a high quality. However, it is not used for bolt manufacturing, and only is used in the carriers. 

  • Tensile Strength: 640 MPa
  • Yield Strength: 360 MPa

Quality Control: HPT and MPI Testing

Mil-Spec materials and parts also undergo rigorous testing. You often will see HPT and/or MPI inspection results, which provides high pressure tested, and magnetic particle inspected results respectively. 

High Pressure Testing is done first and is defined by firing a high pressure cartridge through a BCG. This determines it is capable of dealing with repeat firing. Then the BCG is subject to Magnetic Particle Inspection. During this inspection the BCG is placed in a magnetic field with a magnetically charged liquid solution. This solution will stick to any deformities in the BCG and can be seen under ultraviolet light. Any imperfections could lead to a failure of the part.

Top 5 BCG for a 300 Blackout Reviews

There are a lot of BCG options out there, but the following are specifically rated for .300 BLK caliber rounds and have been tested for efficiency and durability. They span a wide range of budget options as well, and are considered quality picks. 

1. Bravo Company – M16 5.56 Bolt Carrier Group

Bravo Company - M16 5.56 Bolt Carrier Group
  • Cartridge: 223 Remington, 5.56 mm NATO, 300 AAC Blackout
  • Carrier: 8620 Steel
  • Bolt: 158 Steel
  • Mil-Spec: yes

Available in a black, or flat dark earth finish, this full-auto, full Mil-Spec BCG is an incredible product. Made for work, the 158 steel bolt and 8620 steel carrier has been inspected and tested to offer a consistent, powerful option for your AR platform build. 

Easy to wipe clean, it is an easy to install piece and provides consistent firing for all purposes. Made to handle thousands of round and many years of use without showing part wear, it’s hard to beat the quality of the Bravo Company BCG line of products. 

Who This Is For

If you want one of the best in the business, this is a great option. Made to Mil-Spec for durable, lasting use, you won’t need to replace it for years.


  • Incredibly durable
  • Is a great looking finish and wears well
  • Dependable and safe


  • Coating may begin to wear over time

2. PSA 5.56 Premium Full Auto Bolt Carrier Group

PSA 5.56 Premium Full Auto Bolt Carrier Group
  • Cartridge: 223 Remington, 5.56 mm NATO, 300 AAC Blackout
  • Carrier: 8620 Steel
  • Bolt: 158 Steel
  • Mil-Spec: Yes

A top pick for all who try it, the PSA 5.56, full-auto BCG is a durable choice and has a high fatigue strength, MIl-Spec 158 Bolt, and is tested and inspected. Made to withstand heavy use, the phosphate outside carrier coating provides a tough finish for years of use, and has a chrome lined inside.  

Incredibly priced for it’s quality, this is a choice that is hard to beat. Easy to install, it ships dry and will darken once oiled, making it an excellent looking addition to your build.

Who This Is For

When you want the best for your buck, it’s hard to beat Palmetto State Armory parts. This BCG is no exception and provides a quality choice to maximize your budget. 


  • Amazing cost to quality ratio
  • Easy to install and great looking
  • Works wonderfully with all AR builds


  • Finish could be better

3. Rubber City Armory – M16 Bolt Carrier Group Titanium

Rubber City Armory - M16 Bolt Carrier Group Titanium
  • Cartridge: 223 Remington, 5.56 mm NATO, 300 AAC Blackout
  • Carrier: Titanium
  • Bolt: 9310 Steel
  • Mil-Spec: No

When you want something a bit different, lighter, and incredibly durable, a Titanium BCG may be for you. Rubber City Armory prides itself in quality parts and their full-auto, M16 Titanium BCG doesn’t slack. With a proprietary aerospace nitride coating over the titanium carrier, you have an excellent protection for wear and use resistance.  The 9310 steel bolt holds up to abuse and is designed for consistent, long-term use. 

Incredibly lightweight, you get all the power without the weight, making your AR platform easier to shoot for longer periods of time. Although not Mil-Spec, the technology of advanced metal work allows for such a unique product. 

Who This Is For

If you are looking for the lightest BCG you can find, a titanium build is worth taking a closer look at. Built to last, it also installs easily and looks great. 


  • Lightweight build makes a difference. It’s comfortable to use
  • Incredible reload time
  • Reduces recoil significantly


  • May create overgassing and require an adjustable gas block

4. 2A Armament – AR-15 Bolt Carrier Group Lightweight Adjustable

2A Armament - AR-15 Bolt Carrier Group Lightweight Adjustable
  • Cartridge: 223 Remington, 5.56 mm NATO, 300 AAC Blackout
  • Carrier: 8620 Steel
  • Bolt: 9310 SteelBolt: 9310 Steel
  • Mil-Spec: No

2A Armament is considered one of the best in the business, as seen by their quality products. Their BCG stands above the rest in terms of design, adn this choice is no expectation. First off, this is a Regulated Bolt Carrier (RBC) with a gas regulating gate built right into it. It eliminates the need for a gas regulating block, saves on weight, and comes in a nice, drop-in package to help bring your build back to factory specs. 

It also is adjustable for a wide range of buffers, barrel lengths, suppressors, and springs- making it highly versatile. Although it is more costly than a stand alone BCG, you save weight, space, and cost due to the package deal. 

Who This Is For

If you love a personalized AR platform build, this is an amazing way to provide incredible adjustment to your experience. 


  • Excellent for suppressed shooting
  • Amazing adjustability
  • Lessons recoil and adds accuracy


  • A bit costly overall

5. Prime Weaponry – M16 Bolt Carrier Group

  • Cartridge: 223 Remington, 5.56 mm NATO, 300 AAC Blackout
  • Carrier: 8620 Steel
  • Bolt: 9310 Vac-Arc Premium Carburizing Steel
  • Mil-Spec: No

AR15 and M16 build compatible, this full-auto option has a 8620 steel carrier and 9310 steel bolt to provide a durable option to use with a wide range of cartridge choices. The nitride coating creates the strongest plate possible for consistent, accurate use- which makes it quite a steel for the price.

Quick and efficient semi-auto chambering, it both looks good and is an easy install. Made to a tight tolerance, it is an excellent choice for shooters who regularly engage in competitive shooting and plinking. 

Who This Is For

When you are on a budget, but still want one of the best products in the business, this is a great choice to consider. 


  • Incredibly durable and efficient
  • Excellent price point
  • Good looking with a nice finish


  • Not chrome lined
  • May need breaking in to move more smoothly


The Bolt Carrier Group is one of the most important aspects of your AR platform rifle or pistol, and to ensure proper semi-auto firing in a consistent and dependable manner, you need to make sure you have a good one as part of your build. Although there are many you could sift through, the options we’ve provided above are some of the best in the business. Everything from value options that are of excellent quality, to full mil-spec choices are offered – as well as a true RBC to help provide amazing adjustability. 

When looking for a durable choice that can stand up to the regular use of a 300 Blackout, or various other AR-15 caliber ammunition, these BCG picks are worth considering.