The Best 6.8 SPC BCG (2021) – Know Your Bolt Carrier Groups

The 6.8 ammo is an alternative to the 5.56 NATO for an AR-15 or similar rifle. The 6.8 SPC came to be when the 5th Special Forces group was looking for a cartridge that could outperform the 5.56 in combat roles. The 6.8mm Remington SPC was also designed to function in the AR-15 family of rifles with the end goal being a minor loss of magazine capacity and minimal increase in recoil.

It is cheap and easy to upgrade your AR-15 rifle to use the 6.8 round, all you need is a new barrel, magazine, and bolt carrier group (BCG). If you’re looking for the best 6.8 BCG, then you’ve come to the right place. Follow our guide below for the best 6.8 bolt carrier groups.

What is a Bolt Carrier Group (BCG)?

While the most important part of any firearm is the barrel, the second most important part is actually the bolt. The bolt seals the breach of the barrel to force gas pressure from igniting powder to propel the bullet forward.

The bolt carrier group in the AR-15 moves backwards and forwards to eject and reload shells. It also includes some of the key components of the firearm, such as the firing pin, which will strike each shell’s primer to ignite the powder.

The bolt carrier group is a complex arrangement of components in order to perform the functions of chambering a round, sealing the breech, striking the primer, and ejecting the shell. Since the BCG is such a complex part of an AR-15, it is even more important to pick a high quality BCG for your rifle.

The individual components of the bolt carrier group are as follows:

Bolt carrier

The bolt carrier is known as the housing and it comprises the rest of the pieces within it to make sure the BCG work as a whole. The bolt carrier is the part that’s in contact with the buffer and spring. It works to absorb the force for a fired round to rotate and travel backward to extract the spent casing.

Carrier Key

Also known as the gas key, this is a small protrusion located on top of the BCG that allows the gas to pass through it, thus permitting the bolt and extractor to rotate for the entire BCG to travel backward.

Bolt Gas Ring

The bolt gas rings trap the gas as it expands from the fired round and ensures the rifle works smoothly.

Bolt and Extractor

The bolt and extractor are located in the same unit, but they have different purposes. The extractor hooks onto the rim of each round to hold it in place before ejecting it out of the port.

The bolt is star-shaped and located at the front of the BCG. It rotates fifteen degrees to unlock the chamber so that the entire BCG may travel backward to eject the spent round.

Firing Pin

The firing pin strikes the primer of the round each time you fire off the weapon to allow the gas to travel back through the gas tube and into the BCG.

Cam Pin

The cam pin is located in a hole through the carrier and next to the bolt. It functions to stop the bolt from rotating too far as it starts to unlock.

How to Pick the Best 6.8 BCG

MPI

First and foremost, you should never get any 6.8 BCH that does not come certified as MPI, or magnetic particle inspected. The bolt carrier group is literally the beating heart of your rifle and thousands of pounds of pressure per square inch are applied directly to your BCG each time you fire your AR-15.

This is why it is so crucial for you to get the highest quality and most robust bolt carrier group possible. The magnetic particle inspection process means that the BCG was placed in a magnetic field that created two separate electromagnets and is covered in a liquid solution of magnetic particles to instantly identify any cracks or fissures.

This is critical as any cracks or fissures developed on your BCG can lead to a catastrophic failure. A BCG that’s undergone MPI will not have any cracks or fissures at the time it’s sold.

HPT

Aside from MPI, your bolt carrier group should also be high pressure tested (HPT). This means that a high-pressure cartridge rated at or above the SAAMI specifications is fired through the AR-15 before the BCG is sold,

The BCG will only be sold once it has been proven to be in excellent condition after high-pressure testing is complete. A bolt carrier group that’s passed the HPT means that it’ll be able to fire sustained fire from ammunition at or below the SAAMI specifications.

It is advisable to go for an HPT BCG even if you don’t plan on firing high-pressure rounds through your AR-15 as it can give you good peace of mind.

Drop-In

If you want easy installation and not have to pay a professional gunsmith, then you should get a bolt carrier group that comes in a drop-in design. This means that the entire BCG can be literally dropped into the back of your upper receiver for a seamless installation process.

Review of the Best 6.8 Bolt Carrier Groups (BCG)

Given their complexity and the vast array of manufacturers available, we understand that choosing the best bolt carrier group can be a pretty daunting task. Fortunately, we’ve done the work, so you don’t have to. Now let’s start with the best overall BCG available for 6.8 cartridge.

Best Overall

1. Brownells – M16 6.8mm SPC BCG

Brownells is not only one of the top retailers of firearms and firearm products in the country, but they’ve even started manufacturing some components. The company has a wealth of consumer data, knowing what works, what sells, and what people want. They’ve channeled all this knowledge into creating a great line of high-quality products of their own that are affordable.

One such example of a great product is this bolt carrier group. Designed for the 6.8 SPC, this BCG works perfectly with a .224 Valkyrie too. The bolt face of the M16 cut BCG is built of ultra-tough 9310 steel that’s been heat-treated and shot-peened. The carrier is machined from 8620 steel while the extractor construction includes a spring and rubber insert. The gas key screws are also properly torqued and staked.

Overall, this is a complete bolt carrier group that comes in a firing pin, cam pin, and firing-pin retaining pin. It is also finished in matte black nitride to ensure lower friction and better corrosion resistance. Needless to say, this BCG has also been magnetic particle inspected to ensure quality.

You would like this if:

  • You want a BCG that’s been magnetic particle inspected to ensure there are no flaws in its construction.
  • You want a product that features a black nitride finish for reduced friction and improved corrosion resistance.
  • You want a complete bolt carrier group that includes a firing pin, cam pin, and a firing-pin retaining pin.

You might not like this if:

  • You want high-quality and precise construction as there have been some complaints of poor machining.

Runner-Up

2. ToolCraft 6.8mm SPC Nitride Bolt Carrier Group

ToolCraft is a North Carolina company that’s focused strictly on producing bolt carrier groups for AR-style rifles. This is one of those companies that do one specific product and they certainly do it well.

ToolCraft 6.8mm SPC BCG is another product that’s officially designed for the 6.8mm SPC round but also works well with .224 Valkyrie cartridges. In fact, the ToolCraft bolt carrier group is built with even more types of metals compared to the Brownells model discussed above. The BCG keys are built out of 4310 steel while the bolt if made of 9310 steel. The bolt carrier housing itself is constructed from 8620 steel.

Each individual component of the ToolCraft 6.8mm SPC bolt carrier group has been nitride treated to keep it as low friction and corrosion resistant as possible. The gas key is staked utilizing grade eight fasteners, which are some of the very best in the industry.

The bottom line is that the ToolCraft 6.8mm SPC Nitride Bolt Carrier Group is a great choice for a bolt carrier group for your 6.8 AR-15 rifle. This bolt carrier group choice is built from different kinds of durable metals with each individual component being nitride treated to ensure maximum durability and corrosion resistance.

You would like this if:

  • You want a bolt carrier group that’s backed by an outstanding lifetime warranty.
  • You prefer if your bolt carrier group has been nitride treated for excellent durability and corrosion resistance.
  • You want a bolt carrier group made out of different types of durable metals.

You might not like this if:

  • None

3. CMMG, Inc 6.8 SPC/224 Valkyrie Complete BCG

Established in 2002 in Missouri by the Overstreet family, CMMG has one goal and that’s to create quality AR rifle systems that anyone can afford. Every CMMG product is made in the USA from the best materials available, plus they’re even backed with a lifetime warranty against defects in material or workmanship.

This bolt carrier group by CMMG works for both the .224 Valkyrie and 6.8 SPC ammunition. The bolt features 9310 steel with phosphate finish while the carrier is made with 8620 steel with chrome lining on the inside and phosphate finish on the outside. The BCG extractor is made of 4140 steel with a phosphate finish.

This is a great BCG option if you want to give the 6.8mm a try without committing too much money. If you happen to fall in love with the round, you will even be left with a great quality BCG for many years of shooting.

All-in-all, this is an amazing BCG with some of its top features include its affordability and chrome lining. This is without a doubt a great no-brainer option for a good price. CMMG has a solid reputation for practical yet innovative products and it continues to show in this BCG.

You would like this if:

  • You want an excellent value of money that will give you an affordable BCG that lasts for years.
  • You want a BCG that’s backed by a lifetime warranty against defects in materials and workmanship.
  • You want a bolt carrier group that’s’ chrome-lined and phosphate finish for all other components.

You might not like this if:

  • You have other types of rifles as this BCG is available in M16 cut only.

Aero Precision .224 Valkyrie/6.8 SPC BCG, Complete

Aero Precision is based in Washington State and comes from a background of producing components designed for military aircraft and firearms. The manufacturer has channeled and extended their knowledge into producing firearms and components for modern sporting rifles.

The company’s expertise and high standards of quality truly show with this 6.8 SPC bolt carrier group. As with many BCGs, this model also works with the .224 Valkyrie. This M16-cut bolt carrier has been machined from 8620 steel while the bolt itself is machined from Carpenter-brand 158 tool steel.

The BCG features forward assist serrations to seat any stubborn round and the gas key has been properly staked with a black O-ring insert on the extractor. This 6.8 BCG is also shot-peened and black nitride finish coated that lowers friction and reduces the need for frequent lube application and cleaning.

As with all top-quality AR components, this BCG has been HPT tested and MPI marked for maximum durability. This component is manufactured in the USA and weighs only 11.52 ounces.

The bottom line is that Aero Precision is a well-established brand in the world of modern sporting rifle components and their reputation continues to shine with this bolt carrier group.

You would like this if:

  • You want a BCG that features forward assist serrations to properly seat stubborn cartridges.
  • You want HPT tested and MPI marked bolt carrier groups to guarantee the best in terms of reliability.
  • You want a BCG that is black nitride coated to effectively reduce friction and the need for lubrication and cleaning.

You might not like this if:

  • You have other types of rifles as this BCG is available in M16 cut only.

Conclusion

If you’ve come this far, then you should by now have a pretty good idea of what makes a 6.8mm SPC bolt carrier group great. Our list above lists some of the best 6.8 BCGs available on the market that will ensure your AR-15 rifle works smoothly. Hopefully, today’s guide has given you enough information and knowledge required to make an informed decision.

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