How to Clean an M4 Rifle. The M4 carbine rifle is the newest variant of the M16. It is the weapon of choice among most combat units. Its small size and its modifiability make it ideal for urban combat situations. There are many civilian versions of the M4, such as the AR-15 and the Bushmaster .223. To those in the military, care and maintenance of a weapon can mean life or death. To those not in the military, care and maintenance of a weapon can mean years of reliability and shooting enjoyment, free of jams and expensive part replacement.
Clear the Weapon
Drop the magazine, if there is one in the rifle, by pressing the magazine-release button on the left side of the weapon.
Pull back the charging handle and look inside the breech to check for any rounds in the chamber. If there is brass or a live round caught in the breech then lock the bolt to the rear and carefully pry it out.
Place the selector switch on "Safe."
Clean the Exterior
Dust off the outside of the rifle with a brush. A barber or half-inch paintbrush is ideal for this. Use a toothbrush or cotton swabs for the areas around the trigger and front sight-posts.
Remove the hand guards from the barrel by pushing the slip ring towards the receiver while pulling out on the hand guards.
Wipe down the barrel with a rag and clean the inside of the slip ring with a toothbrush or cotton swabs.
Brush off the butt-stock with a dry rag.
Disassemble the Rifle
Check that the bolt is forward. If it is not, hold onto the charging handle and pull the trigger, allowing the bolt to gently ride forward into the breech.
Remove the front and rear takedown pins. The U.S. Army standard is to use your hands, but a tool such as a screwdriver makes it much easier.
Separate the upper and lower receivers.
Set the lower receiver aside.
Pull the charging handle out of the back of the upper receiver; be sure to catch the bolt as it comes out.
Disassemble the Bolt Assembly
Remove the retaining pin from the side of the bolt assembly. Wipe off any fouling with a clean rag.
Tilt the bolt assembly back so that the firing pin slips. Wipe off any oil and carbon fouling with a rag.
Push the bolt into the bolt carrier.
Turn the cam pin 90 degrees and pull out to remove. Wipe it off with a rag and run a cotton swab through the hole in it.
Pull the bolt out of the bolt assembly. Wipe this down thoroughly, and use cotton swabs to clean the grooves on the front and the bolt face. If necessary use a scraper tool to clean off all carbon deposits on the bolt face.
Push on the extractor retaining pin with the firing pin and remove the extractor. Use a cotton swab to clean the extractor, being careful not to drop the extractor spring. If the spring falls out push it back into place firmly.
Clean the area under the extractor with a scraper and cotton swabs.
Clean the Upper Receiver and Barrel Assembly
Push a barrel brush through the breech to the flash suppressor. It is important that you only push things through the barrel in the direction that the bullet travels. Repeat this step as many times as necessary - five to ten times for light cleaning, up to 30 times for a GI standard cleaning.
Run a small arms barrel swab through the barrel in the same manner. Be sure to use a clean swab for each pass. Keep doing this until the swab comes out clean.
Clean the breech or "star chamber" with cotton swabs and a scraper tool.
Wrap a small piece of rag around a toothbrush to scrub the inside of the upper receiver.
Use cotton swabs to clean the outside of the gas tube.
Clean the Lower Receiver
Remove the barrel buffer and buffer spring by pushing the buffer into the butt stock and pressing down on the barrel buffer retaining spring, thus releasing the buffer, which will pop out.
Wipe down the buffer and buffer spring with a clean rag.
Clean the trigger mechanism with cotton swabs and a small brush. Squirting gun oil approved for this purpose into the trigger mechanism helps loosen dirt in this intricate little part. Take your time.
Reassemble the Bolt Assembly
Set the extractor back in its groove. Compress the extractor spring by pushing down on the extractor. Peek in there and make sure the retaining pin holes line up. When they do, gently slide the retaining pin in. This can take a little practice so be patient.
Look at the O-rings on the bolt. Make sure the little gap in each ring doesn't line up with a gap in another ring.
Push the bolt into the bolt assembly. Be sure that the extractor is on the right side of the assembly so the cam pin will fit in.
Place the cam pin into the bolt assembly, then turn it 90 degrees.
Guide the firing pin gently into the bolt through the back of the assembly.
Insert the firing pin retaining pin into the bolt assembly.
Pull the bolt all the way forward. It has to be in this position so the cam pin will fit into the upper receiver.
Reassemble the Rifle
Slide the charging handle halfway into the upper receiver on its rails.
Put the bolt assembly with gas tube towards charging handle into the upper receiver and slide both forward until they lock.
Push the barrel buffer and buffer spring into the butt stock until they are locked in place by the retaining spring.
Place the upper and lower receivers together and push the take-down pins in place. It is easiest to do the front pin first and the rear pin second.
Replace the hand guards.
Items you will need
- A barber's brush or half-inch paint brush
- Clean rags
- Cotton swabs
- Tooth brush
- Barrel rods
- Barrel brush
- Barrel swabs
- M4 approved gun oil