You’re going to experience it someday. Your bolt carrier group will fail. It may be at 2,000 rounds or 10,000 rounds. Invest up front to bridge the gap from the 2,000 to 10,000 round mark. The best bolt carrier group is the CMMG 5.56 M16 Bolt Carrier Group.
What are the best bolt carrier groups?
- CMMG 5.56 M16 Bolt Carrier Group – Best BCG for AR-15/223 Remington/5.56 Bolt Carrier Group
- HM DEFENSE AR15 BOLT CARRIER GROUP – Best .300 Blackout Bolt Carrier Group
- Luth-AR LUTH AR Complete Bolt Carrier Group LR-308 – Best 6.5 Creedmoor Bolt Carrier Group
- Aero Precision 6.5 Grendel/6mm ARC Bolt Carrier Group – Best 6.5 Grendel/6mm ARC Bolt Carrier Group
- .224 Valkyrie/6.8 SPC Bolt Carrier Group, Complete – Black Nitride – Best .224 Valkyrie/6.8 SPC Bolt Carrier Group
#1. CMMG 5.56 M16 Bolt Carrier Group
Check Current Price | Best Bolt Carrier Group 223 Remington/5.56 Bolt Carrier Group
Pros and Cons
Pro’s
- Chrome lined
- Decent price
Con’s
- Phosphate finished
Our experience with the CMMG 5.56 M16 Bolt Carrier Group
This chrome lined BCG is a great starter bolt carrier group. It’s high pressure tested. CMMG is a well known brand in the AR-15 and AR-10 game. Their primary focus is on builds – with plenty of replacement part options.
This bolt would fall under the best 6.5 Grendel BCG
#2. HM DEFENSE AR15 BOLT CARRIER GROUP
Check Current Price | Best .300 Blackout Bolt Carrier Group
Pro’s and Con’s
Pro’s
- Good value for high performance on any budget in your 300 blackout rifle
- Good value for high performance on any budget in your 300 blackout rifle
- Manufactures and designed veteran owned company
- Compatible with .223 Rem, 5.56 NATO, and 300 AAC
- High pressure tested
Con’s
- Relatively unknown company
- Low volumes available
- Expensive
Our experience with the HM Defense AR15 Bolt Carrier Group
The bolt is your standard AR15 bolt carrier group. Compatible with the “big 3” calibers, made from 9310 steel, and has a black nitride finish.
Compared to phosphate coated bolt carrier groups, you’ll be able to rely on this BCG when it counts. It is Mil-Spec quality and a great addition to your next AR-15 rifle.
Some drawbacks. It’s higher price. You can find cheaper models right now though.
If you’re using this with your 300 blackout build, it would be best to use an adjustable gas block to run both sub or super sonic ammunition.
Depending on how often you shoot, you might want to find something cheaper or even on clearance. Worth Firearms is offering this BCG at $140.99 while the MSRP is $175.00. Don’t miss out – quantities are low.
#3. Luth-AR LUTH AR BCG COMPLETE LR-308
Check Current Price | Best 6.5 Creedmoor Bolt Carrier Group
Pros and Cons
Pro’s
- Precision manufacturing and reliability
- Low price
- High pressure tested
Con’s
- Phosphate coating
Our experience with the Luth-AR LUTH AR BCG COMPLETE LR-308
You may not know but the 6.5 Creedmoor round is just fine with the .308 bolt carrier group. There aren’t any specific 6.5 Creedmoor bolt carrier groups. If you find one marketed that way, it’s just a .308 bolt carrier group marketed as a 6.5 Creedmoor bolt carrier group.
The Luth-AR features high quality parts and precision manufacturing. This makes LuthAR bolt carrier groups ideal for maintaining and upgrading firearms. The durability, reliability and excellent build quality of these parts will ensure years of service you can count on.
Built from 8620 Steel, heat treated to Army specifications, Manganese Phosphate finish. It’s a true battle rifle bolt carrier group.
Surprisingly – this bolt carrier group is cheaper than other bolt carrier groups.
While affordable, this bolt carrier group does have a drawback. It has a phosphate coating – inferior to other finishes like the nitride finish and nickel boron finish.
#4. Aero Precision 6.5 Grendel/6mm ARC Bolt Carrier Group
Check Current Price | Best 6.5 Grendel/6mm ARC Bolt Carrier Group
Pros and Cons
Pro’s
- Bolt carrier group is hard to find
- Properly staked gas key
- High pressure tested
- Magnetic particle inspected
- High quality control tested
Con’s
- Hard to find other bolt carrier groups to compare it to.
- Not a con of the BCG, but the 6.5 Grendel and 6mm Arc is a difficult caliber to find ammunition for.
Our experience with the Aero Precision 6.5 Grendel/6mm ARC Bolt Carrier Group
This M16-cut bolt carrier was machined from 8620 steel. It features forward serrations for your upper receiver’s forward assist. Its black nitride finish minimizes the need for lubricants and makes it easier to clean than lesser finished bolt carrier groups.
As described before, finding ammunition for 6mm Arco or 6.5 Grendel are difficult to find. If you’re using this caliber – you know this. This is an excellent upgrade to a higher tier quality bolt carrier group.
It’s surprisingly affordable, comparable in price to other AR15 bolt carrier groups. Which is shocking given that it’s for a specialized caliber that isn’t very popular.
#5. .224 Valkyrie/6.8 SPC Bolt Carrier Group, Complete – Black Nitride
Check Current Price | Best .224 Valkyrie/6.8 SPC Bolt Carrier Group
Pros and Cons
Pro’s
- Forward assist serrations
- Specialized for .224 Valkyrie/6.8 SPC caliber ammunition
- Properly staked gas key
- High pressure tested
- Magnetic particle inspected
- High quality control tested
Con’s
- Specialized caliber that wouldn’t work with other calibers
Our experience with the .224 Valkyrie/6.8 SPC Bolt Carrier Group, Complete – Black Nitride
This M16-cut bolt carrier was machined from 8620 steel (like the 6.5 Grendel/6mm ARC Bolt Carrier Group). It features forward serrations for your upper’s forward assist. Its black nitride finish minimizes the need for lubricants and makes it easier to clean than lesser finished bolt carrier groups.
As described before, finding ammunition for .224 Valkyrie or 6.8 SPC are difficult to find. If you’re using this caliber – you know this. This is an excellent upgrade to a higher tier quality bolt carrier group.
It’s surprisingly affordable, comparable in price to other AR15 bolt carrier groups. Which is also surprising given that it’s for a specialized caliber that isn’t very popular.
Types of Bolt Carrier Groups
There are a few ways to classify or organize bolt carrier groups. By caliber, finish, and semi-auto vs fully automatic.
Caliber specific
There will always be new calibers coming out. To start out, we listed .223 Remington, 5.56 mm, .300 blackout, 6.5 Grendel/6mm ARC, and .224 Valkyrie/6.8 SPC.
Phosphate, Nitride, and Nickel boron
We discussed the differences between phosphate, nitride, and nickel boron bolt carrier groups in this post.
Fully Automatic vs. SemiAutomatic Bolt Carrier Groups
There are two major bolt carrier groups currently available: fully automatic bolt carriers and semiautomatic bolt carrying group.
A full auto bolt carrier group simply indicates that this group is sturdy enough for fully automatic firing. Sometimes you can see them as M16 BCG’s as they’re intended primarily for the full auto model – not the semi auto AR-15.
In contrast, a semi auto BCG can’t handle semi automatic fires. Fully automated group braking bolts are generally more durable.
AR-15 Bolt Carrier Group
An AR-15 won’t work without a bolt carrier group. The firing pin inside the bolt carrier group is what makes the round ignite inside the rifle.
Tell me the Bolt Carrier Group?
A bolt carrier group is a group composed of:
- Bolt
- Ejector
- Ejector spring
- Ejector roll pin
- Extractor
- Extractor pin
- Extractor spring
- 3 mil spec gas rings
- Bolt carrier
- Bolt cam pin
- Bolt carrier key
- 2 Bolt carrier key screws
- Firing pin
- Firing pin retainer pin
A more in depth diagram can be found here.
It is used to ignite the round inside the chamber of an AR-15. Upon blowback, it inserts another round from the magazine into the chamber. The main element of this cycling is from the gas expelled from the round when fired. Upon igniting, the round’s casing is expelled from the ejection port.
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How to Install a New BCG in an AR-15?
It’s easy to instal a new bolt carrier group. Take out the old bolt carrier group like you were going to clean it. Insert the new one. THAT’S IT! There’s usually no bolt assembly required.
Properly lubricate the bolt prior to shooting. Or else you might have a malfunction that’s difficult to fix.
Mil-Spec Bolt Carrier Groups
Mil-Spec is an interesting buzzword for many AR enthusiasts. Military specifications means the weapon is designed for a specific military requirement. Mil-spec means not the best ever, or worst — just the specification for a military contract.
Choosing a Bolt Carrier Group
There are several key considerations when selecting a bolt carrier for your AR-15.
First, choose a trusted manufacturer. BCM’s bolt carrier groups would be more trustworthy than a brand you’ve never heard of. BCM bolt carrier groups is an excellent example of BCG’s that meet military specifications but goes a step beyond, to guarantee quality.
Another key feature of BCM bolt carrier groups is its warranty. BCM offers a 30 day warranty on its products, with store credit offered in situations where warranted.