Are you currently looking for the best bolt carrier group for your .300 Blackout or .300 AAC rifle? If so, then you’ve come to the right place.
Best Overall: PSA Full Auto Bolt Carrier Groups
The PSA Full Auto AR-15 Bolt Carrier Group is built to mil-spec standards and has a long lasting design. It’s constructed out of 158 Carpenter steel with a phosphate finish to ensure ruggedness and durability.
Best Left Handed Pick: Toolcraft Left Handed Bolt Carrier Group
The Toolcraft is a solid pick for a left handed AR-15 bolt carrier group. Constructed according to mil-spec certifications, the Toolcraft is built out of solid 9310 steel with a nice nitride finish for excellent durability and rust resistance.
Best Overall Pick: 2A Armament AR-15 Lightweight Adjustable Bolt Carrier Group
The 2A Armament AR-15 Lightweight Adjustable Bolt Carrier Group is our choice for a .300 Blackout bolt carrier group due to the high quality materials used in the construction of each individual piece. Built out of 7075 aluminum and 8620 steel, this is a durable and yet lightweight bolt carrier group that can easily last you for a lifetime.
A bolt carrier group is something you will need to get if you are building a new AR in .300 Blackout from the ground up. It can also be a wise investment if you planning on upgrading your existing .300 Blackout AR. After all, it’s largely the bolt carrier group that allows your AR to shoot and chamber a new round in the first place. Without it, your AR would literally be a club and nothing else.
In this guide, we will discuss the merits of the .300 Blackout round, the different components that are included in a bolt carrier group, the top qualities to look for in a group, and then our choices for the three best .300 Blackout bolt carrier groups for 2020.
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Why Go With .300 Blackout?
Before we discuss the bolt carrier groups, we need to answer this question: why should you even go with the .300 Blackout round?
The .300 Blackout is also often referred to as the .300 AAC. It is one of many rounds that are made for the AR-15, but is also designed to boost performance of the AR-15 platform over standard .223 Remington or 5.56x45mm NATO ammunition.
When the .300 AAC was first designed, it was intended to give a soldier subsonic performance out of an M4 carbine without having to use 9mm pistol ammunition. Up until then, soldiers had to use 9mm submachine guns if they wanted to have subsonic capabilities.
By switching to .300 AAC, soldiers could use their existing M4 rifles and would only need to switch out a few distinct components. Granted, .300 Blackout ammunition is not nearly as common as 5.56 ammunition is. Fortunately, most parts are fully compatible across 5.56 and .300 AAC AR-15s. Literally the only parts that you will need to swap out are the gas system length and the barrel, read our guide on .300 BLK barrels here. Other parts like a .300 Blackout lower receiver, gas block, stock, magazines, and bolt carrier group are fully swappable between the two calibers.
If you ever want to use a suppressor with your AR-15, the .300 Blackout is one of the very best rounds to use, because it creates distinctively less noise than an AR-15 in 5.56. This can be immensely valuable for a home defense situation, because the loud noise created by a rifle can be severely disorienting within the tight confines of your home. If you use .300 Blackout ammunition for home defense in conjunction with a suppressor, there will be significantly less noise created. This can also be a major advantage if you plan on doing any target shooting on your property so you don’t disturb your neighbors as badly.
If you plan on building a new AR-15 in .300 Blackout from the ground up, one of the most vital components that you will need is the bolt carrier group, since it permits the rifle to fire and cycle in the first place. Let’s discuss what the bolt carrier group is and the different parts that are included in it.
What Is Included In the Bolt Carrier Group?
Before you can know what to look for in a bolt carrier group, you need to learn the parts that make up the group in the first place.
The bolt carrier group is largely responsible for allowing your AR to operate. It’s located in the upper receiver of the AR-15. When you remove the pin that holds the upper and the lower together, you can separate the two halves and then remove the bolt carrier group from the rear of the upper.
When you pull the trigger of your AR-15, the gases generated from the fired round will travel down your gas tube above the barrel. They will eventually find their way into the bolt carrier group. Upon filling up the chamber, the entire group will force itself to the rear against the recoil spring of the rifle.
As the bolt carrier group travels to the rearward position, it will twist in order to unlock itself from the chamber. This then allows the entire action of the rifle to cycle to the rear, thus permitting the spent shell casing to be ejected and a new round from the .300 BLK magazine to be chambered.
If the bolt carrier group did not exist, the firing pin of your AR-15 could not strike the primer of a round and the action could not cycle back in order to permit operation.
The individual components that make up an entire bolt carrier group are as follows:
The bolt carrier is a metal housing of the rest of the components that make up the bolt carrier group. Contrary to what many novices thing, the terms ‘bolt carrier’ and ‘bolt carrier group’ are not interchangeable.
Most bolt carriers are built out of 8620 steel and 9310 steel. They need to be strong and durable enough in order to absorb the gas generated from each new fired round.
The carrier key is also sometimes referred to as the gas key. You will notice it as a little protrusion at the top of the bolt to your AR. It will be hollowed out and is designed to take in the gas as it travels down the gas tube. The carrier key also enables the bolt and the extractor of your AR-15 to rotate so the bolt carrier group as a whole can travel backward to cycle the action.
Bolt Gas Rings
The bolt gas rings are designed to trap gas of each spent round. Without the rings, the gas of each new round would become dispersed throughout the upper receiver of the AR-15. As with the carrier key, the bolt gas rings enable the action to cycle backward.
Bolt and Extractor
The bolt and extractor of an AR-15 are often sold together as a single unit. However, they also serve two completely different functions. The extractor is designed to hook onto the outer rim of a shell casing, and holds the round in place as it is stripped from the magazine and loaded into the chamber. The extractor further holds onto the round as the action cycles back, until it can be ejected via the ejection port. The process then repeats itself.
The bolt has a distinctive star shape to it and is located at the front of your bolt carrier group. It permits the bolt carrier group as a whole to become unlocked. Each time you fire a round, the bolt can rotate by fifteen degrees to free up the bolt carrier group as a whole, permitting the action to cycle backward.
The firing pin strikes the primer of a round each time you pull the trigger. The pin is located at the head of the AR-15 bolt, and without it, the weapon can not fire.
Finally, while it’s the bolt that must rotates to free up the bolt carrier group and permit the action as a whole to move rearward, it’s the cam pin that prevents the bolt from rotating too far. The cam pin is a very small piece located in the carrier in a hole next to the bolt.
Buyer’s Guide For The Best .300 Blackout Bolt Carrier Groups
These are the most important factors to consider when looking for a new bolt carrier group for your .300 Blackout AR-15:
Magnetic Particle Inspected
The number one way to ensure that your bolt carrier group will be durable over the long term is if it comes magnetic particle inspected. Magnetic particle inspection is when the entire bolt carrier group is inserted into a magnetic field and covered in a liquid solution of magnetic particles. This shows any cracks or imperfections in the steel that the naked eye is unable to detect by itself.
If your bolt carrier group does not come magnetic particle inspected, there could be fissures that are not visually detectable, but that could negatively impact reliability. Make sure to only buy a bolt carrier group that is marketed as coming magnetic particle inspected from the manufacturer.
High Pressure Tested
Besides coming with magnetic particle inspection, your AR-15’s bolt carrier group should also come high pressure tested as well. High pressure testing means that the bolt carrier group has been confirmed to handle higher pressure cartridges that are rated above SAAMI specifications.
The idea here is that if your bolt carrier group can handle the higher pressure rounds, it can handle normal rounds like you commonly find on ammo shelves without issue. And if you do end up using higher pressure ammunition anyway, it will be able to handle those rounds too.
A drop-in design for a bolt carrier group means that it can be installed into the upper receiver of your AR-15 without the aid of specialized tools or components. It also means that the entire group as a whole is assembled and ready to drop into the rear of your upper without you needing to assemble anything yourself.
In other words, if your bolt carrier group is a drop-in model, it can be installed into your AR-15 in a matter of seconds.
Last but not least, make sure that your bolt carrier group is built out of high quality and durable materials. Carpenter 158 steel, 8620 steel, and 7075 aluminum are all examples of durable materials that can hold up well over the long term.
While you’re at it, make sure that the bolt carrier group comes with a rust and corrosion resistant finish to ensure longevity as well. Examples of rust resistant finishes include phosphate, hard coat anodizing, and nitride.
Tipp: Do you want to lower recoil? Check out our guide on .300 Blackout muzzle brakes. Installing a muzzle brake on your barrel is one of the most effective way to lower the recoil of your rifle.
The Best .300 Blackout Bolt Carrier Groups
Now that we’ve covered why you need to upgrade your bolt carrier group and what to look for in one, here are our top three picks for a .300 Blackout bolt carrier group in 2020:
PSA Full Auto Bolt Carrier Groups
The Palmetto Full Auto Bolt Carrier Group for an AR-15 is compatible with both the 5.56x45mm NATO and .300 Blackout rounds. Even though this bolt carrier group is marketing as working with fully automatic AR-15s, it can easily work with semi-automatic AR-15s as well. The fact that it is designed to fire multiple rounds rapidly means that It should be very long lasting when firing semi-automatic only.
This bolt carrier group has a phosphate finish with a chrome lining to ensure excellent rust and corrosion resistance. However, it does ship dry from the factory, so the finishing will not be the most attractive looking and make require lubricant to be applied before installing into your rifle.
The PSA is built out of Carpenter 158 steel to mil-spec standards, meaning that it should be compatible with all other mil-spec AR-15 parts and inspected. It also comes mag particle inspected and higher pressure tested to ensure durability and reliability over the long term.
All in all, the PSA Full Auto Bolt Carrier Group is a solid choice for a bolt carrier group. Built out of durable 158 Carpenter steel with a rust resistant phosphate finish, it’s also mag particle inspected and high pressure tested and compatible with all other mil-spec AR-15 parts.
- Fully compatible with mil-spec parts
- Has a very long lasting design
- Built out of 158 Carpenter steel
- Comes high pressure tested and mag particle inspected
- Phosphate and chrome lined finishing is very rust and corrosion resistant
- Comes packed dry, so the fit and finishing are not thee nicest looking (be sure to apply lubricant before using)
2A Armament AR-15 Lightweight Adjustable Bolt Carrier Group
The 2A Armament AR-15 Lightweight Adjustable Bolt Carrier Group is, as the name suggests, a lightweight carrier group. It’s also a drop-in design, and will not require the aids of additional tools or a gunsmith in order to install. Total weight of the entire group is just over seven and a half ounces.
The individual components to this bolt carrier group are made out of high quality materials with rust resistant finishes. The carrier, for instance, is built out of 8620 steel with a nice nitride finish, while the body itself is built out of 7075 aluminum with a nitride finish. It’s the aluminum body of this group that contributes the most to the lighter weight.
Furthermore, this carrier group is fully adjustable with the aid of a T6 Torx tool sold as part of the package. You can adjust the carrier group through the port door, and do not need to disassemble the rifle to do so.
Overall, the 2A Armament AR-15 Lightweight Adjustable Bolt Carrier Group is a solid choice for a .300 BLK bolt carrier group. The various components are built out of 7075-T6 and 8620 steel, with either a nitride or hard coat anodized finish to ensure excellent long term reliability. While expensive, you’re also getting exactly what you pay for.
- Drop-in design
- Very lightweight
- Built out of 8620 steel and 7075 aluminum
- Has a hard anodized and QPQ finish for good rust and corrosion resistance
- Very expensive for a bolt carrier group
Toolcraft Left Handed Bolt Carrier Group
If you need a left handed bolt carrier group for your AR-15, you’ll want to give a close look to the Toolcraft Left Handed Bolt Carrier Group. This BCG is built out of 9310 steel, which provides up to 7% more strength than a Carpenter 158 steel. It has a full nitride finish to ensure excellent rust and corrosion resistance, and comes magnetic particle inspected and high pressure tested.
Built to mil-spec specifications, the Toolcraft is built to mil-spec certifications, which means that it will be compatible with a wide variety of commonly available AR parts. The bolt itself is CNC machined from heavy duty steel, and the extractors are hardened as well to ensure good reliability.
Overall, the Toolcraft is a perfect choice for a left handed AR-15 bolt carrier group. It comes magnetic particle inspected and high pressure tested, and is built to mil-spec certifications. The 9310 steel and corrosion resistant nitride finish ensures solid durability over the long term.
- Excellent choice for left handed shooters
- Durable 9310 steel construction
- Mag particle inspected and high pressure tested
- Built to mil-spec certifications
- Comes with a rust and corrosion resistant nitride finish
- Left handed shooters only
And that concludes our list of the top three best bolt carrier groups for a .300 Blackout AR in 2020.
Any one of the three bolt carrier groups that we have covered here today should be a good choice for your .300 Blackout AR, or alternatively, you can follow our buyer’s guide that we described earlier to help you choose a good BCG as well.
Featured image by u/ccguns