Cleaning the Upper Receiver
Chamber
We recommend using a nylon chamber brush. Bronze or steel chamber brushes will scratch the chamber.
Clean
- 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
- Inspect for significant pitting, gouging, or cracks (a borescope makes this process easier).
- Inspect the locking lugs on the star chamber 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.
Barrel
Chamber to Muzzle vs. Muzzle to Chamber
Always move the cleaning attachment (brush, patch holder, or jag) from the chamber to the bore. This will ensure that all of the crud moves AWAY from the chamber, rather than toward it.
Push vs. Pull
- When you push a cleaning rod down the bore, the rod will bend in the middle until it is supported by the bore. This means that the side of the rod will rub its way down the bore. By pulling the cleaning rod (instead of pushing), the rod will remain straight and will not bend and rub against the bore.
- When you push a cleaning attachment from the chamber to the bore, you will need to pull the rod back through the bore in the direction of the chamber, which can drag debris back down toward the chamber.
To pull an attachment down the bore, carefully feed the empty (without the attachment) cleaning rod through the muzzle and down the bore to the chamber. Use caution when feeding the rod through the muzzle to avoid damaging the crown. Once the end of the rod emerges from the chamber, install the desired attachment onto the cleaning rod (be sure it is firmly screwed into the cleaning rod). Pull the attachment through the bore.
Note that if you use a cleaning jag, you will have to push. Jags are perfectly suited for cleaning when benchrest-level accuracy and precision are needed. We don’t use cleaning jags on our rifles (even our precision rifles), so we stick with pulling.
Brush Etiquette
There are a couple of best practices that should be followed when brushing the bore:
- Always brush from the chamber to the muzzle. You do not want to push crap into the chamber.
- Avoid changing direction with the bore brush, mid-bore. The change of direction can cause the bristles to break and can gouge the bore if using a tight-fitting brush.
- Never pull a bore brush back through the crown. If you are pushing your cleaning rod (rather than pulling it like we do), remove the bore brush from the cleaning rod once it exits the muzzle, before you pull the cleaning rod back through.
Clean
- Install the patch holder onto the cleaning cable or cleaning rod.
- Feed the cable or cleaning rod down the bore. If using a cleaning rod, feed from the muzzle to the chamber. If using a cleaning cable, feed from the chamber to the muzzle and connect the handle to the muzzle end of the cable.
- Install a patch into the patch holder. Saturate the patch with bore cleaner.
- Pull the saturated patch through the bore of the barrel. Discard the used patch.
- Allow the bore cleaner to soak in the bore for up to 15 minutes.
- 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.
- Feed the cable or cleaning rod down the bore. If using a cleaning rod, feed from the muzzle to the chamber. If using a cleaning cable, feed from the chamber to the muzzle and connect the handle to the muzzle end.
- Install the bore brush on the cleaning cable or cleaning rod.
- Pull the bore brush through the bore of the barrel. Remove the bore brush.
- Repeat steps 8 through 10 an additional 4-5 times.
- Repeat 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).
- 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.
- If you used a bore cleaner containing ammonia (e.g. Sweet 762) or you will be storing the gun for a while before shooting it again, be sure to run a patch soaked in oil down the bore as a protectant. At this time, you can also consider lubricating the chamber to prevent corrosion.
Inspect
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.
Muzzle Device
Note that this step can be performed at the same time as the barrel cleaning.
- Spray or saturate the muzzle device with bore cleaner.
- Allow the cleaner to soak in the bore for up to 15 minutes.
- 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
If you are using a muzzle brake, inspect the baffles for bullet strikes (chips, missing baffles, etc.). If there is significant damage, it is best to replace the device.
Upper Receiver
Clean
- 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.
Inspect
- If there is still buildup, repeat steps 2 through 5 until the receiver is clean.
- Look for excessive wear from the bolt carrier group (especially the cam pin). 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 U1.0.
- 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
Clean
- 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 brush, scrub the firing pin, bolt lugs, and bolt face.
- Using a 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. A dedicated bolt carrier bore brush can be used with a pistol cleaning rod or chamber tool handle.
- Wipe all parts with a clean and dry wipe.
Inspect
- If there is still residue on any parts, repeat cleaning of 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. Look for stippling around the primer (may appear as a ring around the primer if you let it go long enough). This is evidence of bad or overpressure ammo, which result in jets of gas escaping around the primer and cutting into the bolt face. 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. A shorter gas system (or piston system) will put more stress on your bolt lugs. For more information, refer to our Gas System Deep Dive articles. Replace the 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 still properly 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.
Charging Handle
Clean
Using a clean and dry wipe, wipe the channel and outside of the stem and the lever(s).
Inspect
- Inspect the stem for kinks, cuts, gauges, or excessive wear. Replace the charging handle, as necessary.
- Inspect the finger for cracking. Replace the charging handle if any cracking is detected.
- 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.
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