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Wood AR 15 Build Bolt Carrier Group: FailZero Semi-Auto BCG

Wood AR 15 Build Bolt Carrier Group: FailZero Semi-Auto BCG

The Bolt Carrier Group: FailZero Semi-Auto BCG 

The big daddy of AR-15 internals (the rest barely even move).

Selecting a Bolt Carrier Group (BCG) for this build was more difficult than expected. As alluded to in the Optic Selection Article, most of our AR platform experience has been in the Military. Those of you who are familiar with how the Military treats its weapons (including cleaning and basic maintenance), know that all the components of the BCG take a beating in operation and then are scrubbed until “too” clean. Your rifle isn’t cycling properly? Squirt some CLP into the action and rack it a few times. As a testament to the platform, M4s/16s/AR-15s actually handle this abuse pretty well.

Needless to say, we had a fair amount to learn about what features are available in a BCG beyond the standard military version. When selecting higher-end BCGs there are basically two enhancements to consider: lighter weight and fancier coating (more durable, easier to clean, cool color, etc).

Lighter weight BCGs generally come in two forms: titanium and lightened steel. Lighten steel BCGs are made from regular steel, they just have holes drilled in them to reduce weight. The advantages of lighter BCGs are faster cycle speeds and less felt recoil. However, they can also reduce the flexibility of your rifle. Since they weigh less, they often require a new buffer spring and depending on whether or not the rifle is suppressed, and the type of ammo being shot, an adjustable gas block. The short explanation of these factors is that a basic, non-suppressed AR-15 (including its gas block and buffer spring) is designed to drive back and then reset a standard weight BCG. The standard gas block therefore, can drive a lighter BCG back with an excess amount of gas and/or a standard buffer spring may have too much resistance for the light BCG to cycle all the way to the rear. On top of that, different types of ammunition have different amounts of pressure and energy, which means they throw the bolt back with varying amounts of force. This is all to say that a properly tuned rifle, with a lightweight BCG and consistent ammo can be a thing a beauty, but a shoot-it-all demo rifle it is not.

We decided on a standard weight BCG.

Wood AR 15 FailZero BCG

Politics aside, it is nice to see those words

Then came the coating selection. This was less straight forward than the weight selection. The jury seems to still be out in the AR-15 community on which coatings are best. Some think all the options are snake oil, others swear by them. Most coatings are intended to make cleaning the bolt easier and to add some lubricity when the bolt is dry. Many will dispute the second part of this statement, but easier cleaning was enough to sell us. The most common coatings available include: Nickel Boron, Chrome, and Ion Bonded. After researching these coatings and reading many arguments about the merits (or snake oil-ness) of each we decided to go with one of the most trusted names in coated BCGs: FailZero.

The FailZero Semi-Auto BCG is a standard weight steel, nickel boron coated AR-15 BCG. It is available in three colors (black, matte and nickel) and comes with all the components installed; ready to drop into any milspec AR-15.

Full Specifications:

Manufacturer: FailZero

Price: $159.99 (MSRP)

Carrier Material: 8620 Steel

Coating: EXO Nickel Boron

Magnetic Particle Inspection: Yes

Live Fire Test: Yes

Wood AR 15 FailZero BCG

It'll never be this clean again

As noted above, FailZero Magnetic Particle Inspects (a quality control process used to look for defects) and live fire tests each of their BCGs. Since the BCG is the major moving component in an AR-15, the most important consideration when selecting a BCG is reliability. Until we run a few cases of ammo through the rifle we won’t really know if the FailZero BCG and its nickel boron coating live up to its reputation. Of course we will provide a full range report once the rifle is assembled so stay tuned to the “Wood” AR-15 Build to learn how she fairs.


As soon as we decided that the FailZero BCG was the one we wanted and reached out to FailZero about sponsoring one for the build, they happily agreed. It is a privilege to work with companies who manufacture their products in the U.S. and are so proud of their craftsmanship that they jump at opportunities to share their work with others. Thank your FailZero!


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