Use this easy-to-follow picture guide to diassemble and reassemble your AR-15's bolt carrier group. This guide applies to all commercial AR-15 and M16 or "mil-spec" BCGs, as well as the AR-10 or DPMS-patterned .308 bolt carrier group. We'll also cover spots to inspect and how to clean your bolt's components to reduce carbon fouling and build-up. Before getting started, it's helpful to have some tools:
- Needlenose Pliers: Useful for reinstalling the firing pin retaining pin.
- Small Punch: Useful for removing and reinstalling the ejector retaining pin.
- Lube/Grease: The BCG's contact and moving surfaces should be coated lightly.
- Wire Brush: Very useful for removing carbon build-up and grime from the bolt.
- CLP/Solvent: A mild solvent will be required for effectively cleaning the entire bolt and carrier.
- Q-Tips and Wipes: A Q-tip can fit inside the bolt to clean out the channel for the firing pin.
Step 1: Remove BCG from Receiver
Remove the rear takedown pin by pressing the pin out of the receiver from the left side. If the pin is tight, the punch or pick comes in handy for getting the pin unseated:
With the pin separated, the upper and lower receiver can separate to allow access to bolt carrier group and charging handle:
Simply pull the charging handle to remove the BCG from the receiver.
Step 2: Remove Firing Pin Retainer Pin
The punch or pliers can assist with this. Pull the firing pin retaining pin from the left side of the bolt carrier.
Once the retaining pin is removed, the firing pin can be removed from the bolt carrier by tilting it vertically:
Step 3: Remove Cam Pin from Carrier
The cam pin captures the firing pin to keep it aligned with the bolt. More importantly, the cam allows the bolt head to rotate and lock and unlock from the barrel extension. To remove the cam pin, push the bolt head into the carrier and rotate the cam pin 90 degrees, then put it from the carrier:
Step 4: Remove Bolt From Carrier
With the cam pin removed, the bolt can slide out from the carrier itself:
Step 5: Remove Ejector Retaining Pin
the ejector is held to the side of the bolt via a small pin. Gently tap the pin out using a roll punch or pick:
Inspection and Cleaning
With the bolt carrier group now disassembled, it's time to inspect our components for signs of wear. We'll also remove the grime, dirt, and build-up of carbon on the components with solvent and a brush. Let's inspect the ejector first:
The ejector spring may have a rubber boot surrounding the coils. You can remove this boot and inspect the coils for any signs of wear. Gently scrub the the ejector and retaining pin with solvent and a brush. Over time, carbon build-up and dirt can make the ejector sticky and unreliable.
Carbon an also build up inside the firing pin channel inside the bolt. Run solvent through the channel and use Q-tips to remove debris.
This section of the bolt is one of the most dirty areas of the bolt carrier group. This area of the bolt becomes sealed inside the carrier to drive the bolt's operation. Naturally, excessive amounts of carbon fouling and grime build up here. A wire brush and plenty of soaking with solvent are required to remove hard build-up.
The gas rings help form that pressurized seal on the rear of the bolt, so they see a lot of heat and pressure. Inspect the rings to make sure they're not cracked or broken. They should rotate and move freely when lightly pressed on with your finger. It's a good idea to soak the rings and lightly brush them to remove carbon debris.
Most bolt carriers have a chrome lining, so carbon fouling doesn't pose as much of an issue here. It's till a good idea to clean the face of the carrier and inside the carrier where the bolt rests with solvent and a brush or Q-tips. Be sure to generously soak and wash out the inside of the gas key, too. It'll be the most dirty part of your entire BCG. Also clean inside the channel for the cam pin to ensure the pin doesn't bind or get caught up.
The last components to check are the bolts securing the gas key to the top of the carrier. Most gas keys are staked to prevent the bolts from coming loose, though it's still good practice to verify the bolts are torqued.
Step 1: Reassemble Bolt and Ejector
To reassemble the bolt, reinsert the ejector and align the retaining pin. Press the pin back in place while applying gentle pressure to the ejector to align the holes. The ejector pin should be flush on both sides of the bolt:
Step 2: Reinsert Bolt and Cam Pin
Reinsert the bolt into the carrier. The bolt needs to be oriented so the ejector is located on the right side of the carrier. The cam pin will only reset inside one of the large holes on the ejector:
Once the bolt is inserted and oriented, lubricate and reinstall the cam pin. Insert the pin so the "T"-shaped portion runs parallel with the body of the carrier, then rotate the cam pin 90 degrees once inserted:
Step 3: Reinstall Firing Pin
With the cam pin oriented correctly, the firing pin can be reinserted:
Once seated, the retaining pin can be reinserted. The pin will fight you, so it's very helpful to keep the pin compressed as you reinstall it. The simplest way to get the pin seated is to squeeze it with a pair of pliers while you press it into the hole in the side of the carrier:
Step 4: Reinsert BCG and Charging Handle
The shaft of the charging handle has two raised bumps which must be aligned with two cut-outs in the upper receiver. Once the handle is inserted, ensure the bolt slides freely with the cam pin on the BCG. Then make sure the bolt is pulled forward as far as possible from the carrier, and reinsert the BCG so the gas key lines up with the charging handle: