How often should the bolt be cleaned of carbon?
What are the signs that carbon needs to be removed?

Don't know how often it is required, but I clean my firearms after every use. It is generally a lot easier to clean a relatively small about of residue and carbon than it is to remove a heavy layer of gunk.

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VCDL, GOA, NRA

As stated by stansdds, it's easier to clean the BCG after every range session rather than letting a bunch of carbon to build up over time.

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Dave Brown
SWCA #3279

A friend of mine’s son asked me to take a look at his Daniels Defense AR-15. “It just doesn’t run right.” No kidding! Everything in the bolt carrier was so encrusted with carbon that it was difficult to disassemble. The amount of carbon on the bolt tail was unbelievable. The rings were complete shot out. Even the firing pin was sluggish in its channel. I don’t like using the ultrasonic cleaner on parts with internal channels I might not be able to dry out properly but this mess left me no choice.

“So when was the last time you cleaned it?” Never

“How many rounds have you put through it then?” At least 2,000 and probably more like 3,000.

I’m not suggesting that you abuse your rifle like this young man did. Please don’t! However, if I showed you the parts prior to cleaning you wouldn’t believe it could fire a single shot.

Cleaning a firearm after every use is a good, disciplined approach. I’m not always that disciplined and there are different levels of cleaning. Wipe it down and bore snake through the barrel - sure, why not? But I don’t disassemble the bolt every time. 250-500 rounds maybe? It will need a good carbon scraping at that point.

If the bolt tail slides smoothly through that hole in the back of its chamber in the BCG, I don’t worry much. There’s a curve just behind the gas rings where the bolt transitions into the bolt tail. If that surface looks uneven, scrape off the crud. Make sure the bolt face is flat and free of carbon. The ejector and extractor need to move smoothly. Pull the bolt forward in the BCG and stand the assembly up on the bolt face. If the rings don’t hold up the weight of the BCG, replace them. Gas rings are a consumable.

I know it’s expensive, but this cleaning tool from Magna-Matic is great. AR bolt tails are not all exactly the same diameter. Sometimes there’s a bit of taper. This tool adjusts to fit any AR bolt. The other end cleans out the channel at the back of the bolt carrier.

MAGNA-MATIC CORPORATION AR-15 CRT-15 CARBON REMOVAL TOOL | Brownells

I didn’t realize that roll pins were disposable items for too long. Do not re-use them. Any time you take the ejector out, use a new roll pin when you reassemble it. And Captain Obvious sez don’t use AR-15 ejector roll pins in 308 AR bolts.

Mostly what The Tin Man said.

I was military trained when it came to the M16A1 and A2 so my ARs and other military style semi autos get cleaned after every range session. It doesn’t take long.

Even if you don’t want to clean the bore, the bolt and bolt carrier slide right out and can be thoroughly cleaned in less than 5 minutes.

An old bronze bore brush and some powder solvent will clean any single range session deposits off the pistol end of the bolt and the inside of the cylinder in the carrier long before they reach a point they need to be scraped off. It’s just quicker and easier to clean after each session than it is to defer it to some future point in time.

Testing gas rings by pulling the bolt forward and standing the bolt and carrier on the bolt face is a good one and has rings are theoretically a consumable item. But if you clean the bolt, etc after each range session the rings last pretty much forever as they experience less wear when properly lubed and not grinding over carbon deposits.

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Along those same lines 2000 round, 5000 round etc “torture tests” are popular, but also farm animals stupid.

Even with the AK-47 Soviet military doctrine was still to clean after every range test their their DIs had white gloves just like ours.

A weapon that will run thousands of rounds without cleaning is of no greater practical value and running one that long without cleaning and lubrication just wears it out long before it’s time. Abusing a weapon like that then carrying it because it’s been “proven” is a whole new level of farm animal stupid.

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In many respects it’s the same issue as the dreaded “carbon ring” in a .357 that is used to shoot .38 Special. I do that a lot but have never gotten a carbon ring as I clean my revolvers after each range session and a ring never gets a chance to build up in the first place.

I clean ARs after every use. I take the bolt out of the bolt carrier group and put all of it in a pan with just enough kerosene to cover everything and let it all soak while I clean the bore, etc. I use an inexpensive Brownells bolt radius scraper to remove carbon, but if you clean after every shooting session, any carbon buildup will be pretty minimal.

With the inside of the bolt carrier group still wet with kerosene, I use a few patches on a .22 slotted rod tip to clean it. I clean the bolt face with patches. Wipe everything down and lubricate lightly with whatever lube you have on hand and re-assemble. It takes a number of cleanings for the kerosene to get dirty, so I pour it back in a container for next time.

According to the U.S. Army after each shooting. You remove the bolt from the bolt carrier and scrape off any carbon fouling.

As to how many rounds you can fire before given the bolt attention, around a thousand using military grade ammo in a military grade firefight.

Keep it wet with oil and that will keep fouling soft and easy to clean off. Ballistol is all I use on the Bolt group. Head it off before it happens . A dry BG will carbon up like a car engine. I break my bolt down every 100 rounds for a extra cleaning and fresh lube. Lube the BG and be happy!!

I have to respectfully disagree. The AR platform is supposed to run fairly dry. Also, breaking down the bolt every 100 rounds seems excessive and you better have a good supply of ejector roll pins on hand. That’s a 1-time use item.

ETA: if SOTAR and Vickers Tactical both say “run it wet” then I am going to listen. I started shooting a bolt action .22 almost 60 years ago, but old dogs can learn … sometimes.

AR15 is a dirty girl and she likes to run wet. Keep the BCG soaked with CLP. Clean it every few hundred rounds or so. Cleaning after every range session is a waste of time. The best tool for cleaning a BCG is an ultrasonic cleaner, then blow dry with compressed air. Barring that, you will have to scrape.
But if you really want to break free from the carbon fouling monkey, upgrade to a Nickle-Boron or Titanium Nitride BCG. Carbon fouling wipes off like cooking eggs in a non-stick pan.

I clean my AR after every outing. I clean the carbon off the bolt with a worn out brass bore brush, wipe it down and reassemble the BCG. I don't put any lube on the bolt when I install it back in the carrier, I figure the lube will just burn off anyway and possibly gum up the works. I do put some LSA on the BCG before I reinstall it in the upper. I've been doing it this way for over 40+ years with no issues.

Why ask a question that you have to know that youre going to get many different answers and end up just doing it your own way in the end. Oh, by the way most of those answers will be wrong and if you follow the wring one(s) then you are now right there with those giving bad info when you start giving advice

Three references:
School of the American rifle
Chris Bartocci of Small Arms Solutions
US Army TM for the M16 TM9-1005-249-23P
You will get no better help.

Bolt/carrier cleaning can be greatly simplified by the use of a gadget called the CAT M4 tool. Makes cleaning the bolt tail and the bolt recess in the carrier easy. The amount of crud that can develop is largely dependent upon how many rounds & what powder they were loaded with.

I'm of the clean after each use school. How detailed the cleaning is depends upon how many rounds fired. 1-5 or so rounds is pretty much bore & bolt face, but I use low residue powders.

"Wet" is not a defined term or condition. What it doesn't mean-at least in my experience- is dunking the bolt group in a quart of lube. Somewhere on here is a post on this that includes pics of the lube diagrams from the Army field manual. Use it.

Deep in the last century I was introduced to Dri-Slide as the preferred firearms lube. I still use it. It's a dry film moly-disulfide lube in an evaporative carrier. Goes on wet and dries. When dry, stuff doesn't stick to it, making cleaning much easier. You might have to go to an industrial supply to find it. My local source didn't even know he was listed as a dealer. I had to buy a case of it, but I gave some away as gifts and kept the rest. The kids will get any remainder when I'm gone.

I have no idea what ammo was being used so that there was a significant amount of crud on/in the BCG after 3K rounds, and that it was enough to cause functioning problems, but that is utterly weird. I did a collection of carbine classes (about 10) with the late Pat Rogers (Sgt., NYPD, retired; CWO 2, USMCR, retired). He had (many) rifles that had gone tens of thousands of rounds without cleaning and only lube. I'm pretty sure that with a decent search engine you can find his writings about "Filthy 14" (the rack number) in SWAT magazine. Pat was generally opposed to the white glove stuff taught in the military as that kind of cleaning was hard on the rifle.

I saw a lot of rifles that went many thousands of rounds among my classmates. A good quality AR platform (and as I recall, DD is in the first tier group with BCM and I am pretty sure Colt) should go at least 10,000 rounds with only lube and never bat an eye. Mine would go 1500 or so in each 3 day class. I would clean it when I got home for a variety of reasons, but functioning was never one of them. I just use squirt bottles of SLIP; if the rifles was too wet it would just blow the lube out or burn it.

I am pretty sure Dean Caputo would take the same basic position.

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NHI, 10-8.

Around the time of the Gulf War the “run it dry” idea became popular. The rationale was that a dry bolt carrier would not collect sand and dirt.

It didn’t work so well.

Any semi auto rifle with metal to metal contact needs to be run wet.

Was it a one piece gas ring or three individual ones? That seems like a short interval for the gas rings, was the bolt failing to lock? Was the bolt able to support itself when you tested it? Sweeny recommends ring replacement at the 5K mark in his book on gunsmithing the AR.

Also, how often are you removing the ejector? Per the TM, you need to be careful not to bend the ejector spring when installing it.

What ammo and lube was he using through the rifle?

We were taught to run our M16A1’s dry in BCT at FLW in 1973. I agree though with running them wet.

It’s the Herpes of the AR-15/M16/M4 world, it seems that it is an idea that just keeps coming back.

In 1985 it was definitely “run it wet”. So at a minimum it went from dry, to wet, to dry, to wet again in US service.

I also have an aversion to the "white glove inspection clean" mind set. Might have it's place as a prep for long time storage, but nowhere else. We had a lead armorer who mandated that after every use. He got canned after excessive wear due to abusive cleaning required major parts replacement on service revolvers. The next lead got approval for ultra sonic cleaners to backup individual cleaning efforts during the mandated semi-annual armorers inspections for all firearms. Saved us a bundle in the long term.

You can get a lot of improperly cared for equipment to keep running by slathering on lube. Even some lubes that contribute to problems. Doesn't make it right or a behavior to copy. Back when I smithed, at the end of each competition season, I'd get a number of 1911s in that "need the trigger redone". No they didn't. What the user had done was pour on the lube instead of cleaning. The problems were due to accumulated powder particles floating about between moving parts and interfering with proper operation.

FWIW, the one product that allegedly cleans, lubes & protects really doesn't do the best job. While they might be loved by logistics geeks and the poor souls who have to lug all their gear on their backs, separate products typically do a better job. When I went to various training programs I made sure I cleaned & lubed my firearms (my preferred lube) before class started. My rifles never got cleaned until I got home and experienced neither malfunctions nor difficult cleaning.