To ensure your AR-type rifle or pistol runs effectively, it's critically important to occassionally field-strip and clean the bolt carrier group and its individual components. Use these written instructions and pictures to learn how to properly disassemble the BCG. Reference the photos for the "hot spots" and where carbon fouling and dirt tend to build up the most. We'll also point to areas you should inspect for maintenance and repair.
BCG Disassembly: Tools Required
To safely disassemble and clean the bolt carrier and its components, you'll want some basic hand tools and some cleaning equipment:
- Needlenose pliers (recommended)
- Small punch (recommended)
- Lubricant or oil (required)
- Wire brush (Avoid steel; bronze is best)
- Q-tips or pipe cleaners (recommended)
How to Strip the BCG
Remove Bolt Carrier From Receiver
To remove the BCG from the receiver, press the rear takedown pin out fully. Pull the charging out to remove the bolt carrier group.
Remove the Firing Pin Retainer
Pull the firing pin's retainer from the left-hand side of the bolt carrier. This small pin is difficult to remove, so a small punch or needle-nose pliers helps.
Drop the Firing Pin from the Bolt
Remove the firing pin from the bolt. Rest the carrier vertically, and the pin should drop freely. If the bolt is excessively dirty, you might need to remove the firing pin with needle-nose pliers.
Remove Cam Pin from Carrier
The cam pin controls the rotation and movement of the bolt. With the firing pin removed, the cam pin can be pulled from the carrier. Push the bolt into the carrier fully. Then rotate the pin 90 degrees and remove it.
Remove Bolt From Carrier
With the cam pin removed, the bolt can be removed from the carrier. Simply grab the bolt face and pull it out from the front of the carrier.
Remove Extractor From Bolt
The extractor is retained by a small pin. The pin can only be removed with a small punch or similarly sized pin. With the pin removed, the extractor will fall free from the bolt.
Inspecting and Cleaning The BCG
The extractor is a good place to begin with inspection and cleaning. Flip the extractor upside down and remove the small rubber boot surrounding the extractor spring. Inspect the spring for signs of wear. Cleaning the area with solvent and a wire brush. On the opposite end of the extractor, inspect the small channel that grasps the lip on shell casings. Sometimes, carbon fouling can build up inside the channel and it should also be cleaned with solvent.
Inside the body of the bolt, carbon build-up can restrict the movement of the firing pin. This can result in light strikes. Clean inside the channel where the firing pin rests. A Q-tip or pipe cleaner is sufficient.
In maintenance and reducing carbon build-up, the most problematic part of the entire BCG's system is the back-end of the bolt itself. This area, located behind the three gas rings, is subjected to high amounts of heat, pressure, and gas from the AR's gas system. This area is responsible for generating the pressure required to unlock and actuate the bolt itself. You may need to soak the portion of the bolt and clean it thoroughly with a wire brush to remove carbon build-up.
It's important to inspect the gas rings for wear, too. Carbon can build up between the rings. Check each ring for cracks, and ensure the rings rotate freely when pressed. Lightly clean them with solvent and a brush. The small holes in each ring to not need to be aligned for the BCG to operate reliably.
The bolt carrier itself does not need to be cleaned as thoroughly as the bolt, though excessive carbon build-up should be removed from the front half, particularly around the cam pin area, the cavity where the bolt rests, and the gas key.
While cleaning the carrier, inspect the gas key bolts to verify they're torqued. Most keys' bolts come staked (held in place permanently by stamping the metal around the bolt head), though not always. If your gas key bolts are loose, they should be torqued to 50 to 58 inch-pounds.
Reassembling The BCG
Reinstall Extractor on Bolt
To reinstall the extractor, press it into the channel on the bolt to align the pin holes. Gently tap the retaining pin back into place. A small punch may be helpful.
Reinstall Bolt and Cam Pin
Reinsert the bolt into the carrier. Only one of the two large holes in the side of the bolt is correctly sized to accommodate the cam pin, so you may need to rotate the bolt to ensure the correct hole is being used for insert the pin. Orient the cam pin so the head is parallel with the carrier's body, then reinsert the cam pin. Rotate the cam pin 90 degrees so it's oriented as shown above, to accommodate the firing pin.
Reinstall Firing Pin and Retainer
Drop the firing pin into the bolt through the carrier. Ensure it is fully seated by pressing down on the rear of the pin.
The retaining pin can now be inserted to capture the firing pin. The pin needs to be compressed so it clears the pin and carrier. This can be done with a set of needle-nose pliers. Grasp the pin near the head and squeeze it while pressing it into place. It helps to try to orient the pin up toward the top of the carrier to assist.
Reinstall BCG and Charging Handle
Reinstall the BCG and charging handle. You must first partially insert the handle into the receiver, then the bolt. The bolt must be extended in the forward position at the front of the carrier to be reinstalled. Press the assembly into the receiver fully, and connect both receivers together via the takedown pin.
Perform a Functions Test
Verify the weapon is empty before performing a functions test.
Verify the trigger, hammer, and bolt carrier assembly work as intended. Charge the weapon by pulling the charging handle back. With the safety lever on "FIRE", squeeze the trigger. The hammer should fall. Keep the trigger squeezed and pulling the charging handle again to re-cock the hammer. Release the trigger. You should hear a click or pop as the disconnector releases the hammer, allowing the sear to capture it, keeping it cock. Squeeze the trigger again to verify the hammer drops.