How to Clean an AR Upper Receiver
Clean and Inspect the Chamber
- Saturate the chamber with bore cleaner. You can use a spray bottle, dropper, or a saturated patch, wipe, or cotton swab.
- Allow the cleaner to soak in the chamber for up to 15 minutes.
- Install the scraper tool onto the chamber tool handle.
- Insert the scraper into the locking mechanism of the barrel extension. Rotate the tool in a clockwise direction (counterclockwise will unscrew the attachment from the handle) for several revolutions to scrape the buildup.
- Remove the scraper from the chamber tool handle. Install the chamber brush onto the chamber tool handle.
- Insert the chamber brush into the chamber. Twist the brush in a clockwise direction for several revolutions.
- Inspect the chamber. If there is still residue adhered to the chamber that has not been loosened, repeat steps 3 through 6 (scrape and brush).
- Remove the chamber brush from the chamber tool handle. Install the chamber mop onto the chamber tool handle.
- Insert the chamber mop into the chamber. Twist the mop in a clockwise direction for several revolutions.
- Inspect the chamber. If there is still residue adhered to the chamber, repeat steps 3 through 9 (scrape, brush, and mop). If there is still loose material in the chamber, repeat step 9 (mop).
- Remove the chamber mop from the chamber tool handle. Install a clean star chamber pad onto the chamber tool handle.
- Insert the chamber pad through the locking lugs on the barrel extension and twist for several revolutions. This will remove any lingering debris from the barrel extension locking mechanism.
- Inspect the chamber.
- Inspect for significant pitting, gouging, or cracks (a borescope makes this process easier).
- Inspect the locking lugs on the barrel extension for excessive wear or missing/chipped locking lugs.
NOTE: If there is damage to the chamber, you may need to replace your barrel. Failure to address structural issues in your chamber may result in catastrophic failure of the firearm in the field.
Clean and Inspect the Barrel and Muzzle Device
- Install the patch holder onto the cleaning cable.
- Install a patch into the patch holder. Saturate the patch with bore cleaner.
- Feed the cable through the barrel from the chamber end until it emerges from the muzzle (always feed cleaning brushes/patches from chamber to muzzle). Connect the pull handle to the cable.
- Pull the saturated patch through the bore of the barrel. Remove the pull handle from the cable and discard the used patch.
- Allow the cleaner to soak in the bore for up to 15 minutes.
- While the bore is soaking, inspect the muzzle device.
- If you are using a muzzle brake, inspect the baffles for bullet strikes (chips, missing baffles, etc.). If there is damage, it is best to replace the device.
- If there is fouling or burnt powder, wipe the muzzle device with a patch saturated with bore cleaner. Allow the bore cleaner to soak in.
- After up to 15 minutes, run another wet patch down the bore per steps 2 through 4.
- Remove the patch holder from the cleaning cable. Install the bore brush on the cleaning cable.
- Feed the cable through the barrel from the chamber end until it emerges from the muzzle. Connect the pull handle to the cable.
- Pull the bore brush through the bore of the barrel. Remove the pull handle from the cable.
- Run the bore brush down the bore per steps 9 and 10 an additional 4-5 times.
- Remove the bore brush and install the patch holder onto the cleaning cable.
- Run a few wet patches down the bore per steps 2 through 4 until the patch emerges somewhat clean (it is not necessary that it be spotless…you will blow through a lot of patches if this is your goal).
- Now repeat steps 2 through 4 with a dry patch (DO NOT saturate it with bore cleaner) 2-3 times to remove the remaining bore cleaner.
- Using a nylon bristled brush, scrub the baffles of the muzzle device, if applicable, to remove any powder residue. Wipe dry with a dry patch or wipe.
- Inspect your bore. It is best to use a borescope for this process to ensure a thorough inspection of the entire bore. If you do not have a borescope, you may shine a flashlight in the chamber end of the barrel and observe from the muzzle end. Note excessive pitting, gouging, obstructions, or abnormal/uneven wear of the lands. Replace the barrel if necessary.
Clean and Inspect the Upper Receiver
- Using a clean and dry wipe, wipe out the inside of the upper receiver. Use a pick or screwdriver to push the wipe into tight spaces.
- With the bulk of the old lubricant removed, spray cleaning solution (NOT bore cleaner) onto the inner surfaces.
- Allow the cleaner to soak in the receiver for 15 minutes.
- Using a nylon bristle brush, scrub the inside of the upper receiver to loosen any buildup.
- Wipe the cleaner out of the receiver per step 1.
- Inspect the upper receiver.
- If there is still buildup, repeat steps 2 through 5 until the receiver is clean.
- Look for excessive wear from the bolt carrier group. If wear is extensive, you may need a new upper receiver.
- Look for cracks in the receiver. If cracks are observed, you may need a new upper receiver.
- Inspect the pivot and takedown pin lugs for excessive wear.
- Inspect the forward assist for any gunky buildup. If necessary, remove the forward assist per the instructions in the How to Build section Step U2.0.
- Inspect the forward assist pawl for cracking or excessive wear. Depress the forward assist button for this step. Repair or replace the forward assist or pawl, as necessary.
- Inspect the end of the gas tube protruding into the upper receiver. Look for dents, cracks, or splitting. Replace the gas tube, as necessary.
- Try to rotate and pull the gas tube. If the gas tube comes loose, you may have a missing gas tube roll pin or a broken gas tube. Replace or repair the gas tube, as necessary.
Clean and Inspect the Bolt Carrier Group
- Spray all parts of the BCG with cleaner (NOT bore cleaner). We recommend doing this in a parts tray to minimize the mess.
- Allow the parts to soak for 15 minutes.
- Using a bronze bristle brush, scrub the firing pin, bolt lugs, and bolt face.
- Using a nylon bristle brush, scrub the remaining parts. Be sure to scrub the inside of the bolt carrier (where the bolt sits) and the cam pin channel on the carrier.
- Wipe all parts with a clean and dry wipe.
- Inspect all parts carefully.
- If there is still residue on any parts, repeat steps 1 through 5 for the affected part(s).
- Inspect the bolt carrier for chips, gouges, cracks, or unusual wear. If you are using a lightweight aluminum bolt carrier, be particularly attentive for cracks. Replace the bolt carrier as necessary.
- Inspect the bolt for unusual wear of the bolt face. If there is unusual wear/indentation of the bolt face, you may have an over-pressurization issue. Refer to Troubleshoot for more. Replace the bolt as necessary.
- Inspect the bolt body for cracking or fracturing. Replace the bolt, as necessary.
- Inspect the bolt lugs for excessive wear, damage, chips, or missing lugs. Replace teh bolt as necessary.
- Inspect the open end of the gas key for bending, chipping, or splitting. Replace the gas key or bolt carrier, as necessary.
- Inspect the gas key screws. Ensure they are present (not missing), are flush with the top of the gas key, are staked, and the screw heads are intact. Repair or replace the gas key screws, as necessary
- Inspect the firing pin for chipping, cracking, or excessive wear of the striking point. Replace the firing pin, as necessary.
- Inspect the firing pin retaining pin for splitting, bending, or cracking. Replace the firing pin retaining pin, as necessary.
- Inspect the gas rings for fracturing (there should only be one split in each gas ring). Replace the gas rings, as necessary. Note that we will verify the wear of the gas rings upon reassembly of the BCG.
- If you have done a detail strip of your BCG, inspect the extractor for chipping, cracking, or fracturing, especially at the claw. Inspect the extractor spring for deformation. Replace the extractor and/or extractor spring, as necessary.
Clean and Inspect the Charging Handle
- Using a clean and dry wipe, wipe the channel and outside of the stem and the lever(s).
- Inspect the charging handle for unusual wear or damage.
- Inspect the stem for kinks, cuts, gauges, or excessive wear. Replace the charging handle, as necessary.
- Inspect the latch for excessive wear or damage. Repair or replace the charging handle, as necessary.
- Verify the function of the lever(s). Repair or replace the charging handle, as necessary.