Managing the Carbon Ring
Updated: Dec 3, 2022
The carbon ring is fouling that develops at the end of the chamber and continues into the first couple inches of the barrel. What differentiates this carbon fouling from regular powder fouling is the tremendous heat and pressure that develops in the chamber bakes this powder fouling into an almost ceramic coating. Each additional firing builds layers of this “hard carbon”.
The hard carbon first forms in the neck area of the chamber. The word “ring” comes from the initial shape of this debris when looking in the chamber with a borescope. It is important to remember, this same hard carbon is also baked in the first couple inches of the barrel.
When left untreated, the carbon ring can lead to pressure spikes and negatively affect precision and accuracy. This is especially true in the chamber if the hard carbon develops thicker than the case neck. Different powders can build up this fouling faster than others. Depending on the type of shooting you do, this may influence the powder choice.
Three Important Notes:
First: A borescope is a must If a shooter truly wants to know if they have developed a carbon ring and/or if their cleaning process is being effective against this admiral foe. However, I will outline my process, which has been proven with a borescope, for those who do not own one.
Second: The carbon ring does not have to be completely removed for optimal precision and accuracy. However, it does have to be managed so it does not get out of control. In the neck area of the chamber, the shooter does not want the carbon to build up thicker than the case neck. Otherwise, It is difficult to put a numerical measurement to the limit of the carbon ring. The target will tell you when there is too much hard carbon in the barrel.
Third: The normal routine for cleaning a barrel usually does not get rid of the hard carbon. Removing the carbon ring takes some extra time and effort compared to cleaning the fouling out of the rest of the barrel. Point being; cleaning the barrel and cleaning the carbon ring are two separate processes.
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Procedure For the Hard Carbon in the Neck Area of the Chamber
As with most cleaning projects, regular cleaning is easier and more effective than a “once a year” deep cleaning. This is especially true with hard carbon. If you have never removed the hard carbon, the first go-around is going to be very work and time intensive. However, once you get the carbon ring under control, future cleanings will be quicker and easier.
The following procedure was developed over years of trial and error. With a borescope, I would check the results of a particular method, making needed adjustments each time. This is the procedure I currently use at tournaments and at home. The exception being; I will confirm at home using a borescope, that the majority of the hard carbon is out.
Step 1: Let it Soak
When tackling the carbon ring in the neck area the first thing I will do is wrap a cotton patch around a bore sized nylon brush on a short cleaning rod. Soak this patch with solvent (Personally, I use Bore Tec Eliminator) then insert it into the neck area of the chamber. Spin and short stroke this patch for fifteen seconds or so. Let this solvent work for a couple minutes. Due to time, I will let this soak a little longer at home than I would at a match.
Experience Tip: I marked where the rifling starts (for my competition rifles) on my cleaning rods. This is a visual indicator of the location of the brush in the barrel.
Experience Tip: Make sure the muzzle is pointed down hill. The downward angle will keep the solvent from running back through the chamber and getting into the trigger.
Step 2: Spin Bronze brush
On the same short cleaning rod, attach a bronze brush that is roughly the same size as the neck dimension yet larger than the bore diameter. (For example: on my 30BR barrels I will use a .338 bronze brush. The chamber neck has a dimension of .330 and a bore diameter of .308.) Add some solvent on the brush and spin in the neck area of the chamber, working it back and forth as it is spinning. I will do this for roughly thirty seconds.
Caution: Do not force this brush anywhere, it can get stuck. Experiment with different sizes until you feel comfortable.
Step 3: Spin the Patch
Replace the bronze brush with the same nylon brush used before. Wrap a clean cotton patch around this nylon brush. Use a back and forth while spinning motion to clean the neck area of the chamber. This may take a couple patches.
Step 4: Confirm
At home, I will confirm using a borescope if a repeat of the above steps is needed. It is not unusual for this hard carbon to require two cycles. Due to a lack of time, I will only do the steps one time while at a match. My goal is to keep the carbon ring in check until after I get done with the tournament, then I can do a more thorough job.
Procedure for Hard Carbon in First Couple Inches of the Barrel
Step 1: Clean Barrel Like Normal
Use your normal barrel cleaning routine. For a more detailed example on my process see the Blog titled: Cleaning Part 2: Develop your cleaning process. There is also a YouTube video embedded in the Blog. https://www.ctdshooting.com/post/cleaning-part-2-developing-your-cleaning-process
Step 2: Focus on First Couple Inches
Experience Tip: At a match, I would not do step 2. There simply is not enough time. This is why I make sure the majority of the hard carbon is out before the match starts. Once I get home, I will do step 2.
Using a short cleaning rod, put a small amount of your favorite cleaning paste (I use Iosso) on a cotton patch wrapped around an undersized nylon brush. Short stroke the first couple inches. This patch will turn dark black.
Replace this patch with a clean cotton patch and short stroke again. Repeat with as many clean patches as needed. The color on the patches will turn from black to gray to white. Once the patches stay white (or very little gray) you are done.
Experience Tip: I will not use a bore guide while performing step 2. I have found too much of the paste goes inside the bore guide resulting in not enough in the barrel and a mess to clean up.
Caution: When using an abrasive cleaning paste, be careful not to cross the line between scrubbing the fouling versus polishing the barrel. This is when a borescope is worth the money.
Step 3: Flush the barrel
After using bore paste, always follow up by using your favorite solvent on a cotton patch to “flush” any remaining paste from the bore. You do not want to send a bullet down a bore with cleaning paste in it.
In Case You're Wondering: I will use bore paste once, maybe twice, a year the whole length of the barrel.
Hunting vs Competition Rifles
I send roughly 120 rounds down each barrel during a typical tournament. I will clean at the halfway mark, managing the hard carbon in the chamber. Once I get home, I will do a better job on the carbon ring in both the chamber and barrel.
The type of hunting you do will dictate how often you need to tackle the carbon ring. If you are shooting prairie dogs, this may mean twice a day. If you are a deer hunter that puts five rounds down their barrels a year, you might need to do this process once every ten years. Just remember; the carbon ring is a lot easier to manage with regular cleanings.
Rifles that have not been cleaned for several years may have hard carbon that is embedded into the steel of the barrel. Trying to completely remove this carbon may cause more harm to the barrel than what the accuracy gains are worth. In these situations, follow the same steps as outlined above, but realize the hard carbon stains are probably permanent. In this case, the goal is to make the rifle safe to shoot. Any improvements in precision are an added bonus. Embedded hard carbon is an unfortunate consequence of neglect.
Managing the carbon ring in a barrel is similar to using a chain on a chainsaw. We want that chain to be as sharp as possible when starting the job. Even though the chain is dulling on every cut, it is still accomplishing the job with ease. We do not need to sharpen the chain every time we cut one piece of wood. However, once the chain starts to show the signs of dulling, it is time to sharpen. If we keep using that chain and “burn” through the wood, it is going to be very tough to sharpen and we may actually ruin the chain.
Every barrel has a “precision window”, the number of shots, between cleanings, where the groups are the tightest. Even though fouling, including the carbon ring, is building up on every shot, there is no noticeable loss in precision. Eventually, fouling will start to show its effects on the target. At this point (better yet, before) it is time to clean. Do not keep “burning through the wood”.
This is not the only procedure that is effective on hard carbon. It is simply one procedure that I have tested and proven. That is exactly what Connect The Dots is about; sharing proven accuracy and precision guidelines. You can then pick and choose what you want to add to your current procedures to make them better. Until next time, enjoy the experience.