Just because it’s black -- doesn’t mean it’s carbon.   Something to consider......

CHRIS
RGChristensen

I'll jump in here but my comments may not be germane to the problem of barrel carbon deposits. First of all oxalic acid will not dissolve or remove 
hard carbon accumulations so forget it..

In my hot rod days where we built high cam performance street rods carbon was a big issue as we did more cruising, stop light idling and short burst burning rubber high rpm displays. Carbon build up on valves and cylinders was a constant problem. 

The treatment for top end carbon was a slow running hose or can of water down the carb with somebody on the pedal .keeping the rpm's up. Engine had to be hot and the results was a stream of black carbon steam out the tail pipe. 30 to 45 seconds of this duesch and the engine ran sooo smooth. 

How does this apply to rifle barrels I don't know

Rick

Whatever you do with oxalic acid make sure it's done outside, and wear a respirator! That stuff is really nasty and can cause lung damage easily. I used it to bleach a gun stock and even small whiffs take your breath away!

Wayne a bit about carbon scale removal that I know for a fact

Working in the marine trades both commercial and yacht construction and maintenance we use Oxalic acid a lot. Teak decks are easily brought from weathered gray to gold with Oxalic if used in direct sunlight brushed across the grain. It's the UV that boosts Oxalic's efficiency. It's also probably the most effective wood stain remover on spruce or pine masts, again with sunlight. Boatyard hull waxing and cleaning crews depend on Oxalic to remove engine exhaust and industrial stains carried by rain. Nothing like it. 

But it's not a ' Carbon Scale Remover '. Understand that decarbonizing big ship and commercial fishing vessels, factory stacks, etc. is big business these days after the EPA and state coastal commissions have hit shipping companies with big fines for carbon emissions and related fires when a ship clears her stack. At night when they do that it's a shower of fiery embers. A lot of these carbon cleaning companies are essentially frauds using gimmicky names and solutions that won't do anymore than Oxalic acid. 

Removing baked-on carbon these days almost always is done with very strong surfactant solutions formulated around caustics like Potassium Hydroxide ( KOH) or Sodium Hydroxide/ lye ( NaOH) and some other proprietary stuff. Lately there are a few chemical companies adding amino acids, seaweed extract etc. that is claimed to go in and break down the carbon to base bond so the scale breaks loose. Many more modern big ships use a CCS ( carbon capture systems ). Engine exhaust, normally heavier crudes, is routed into big capture tanks that contain a special solvent. This solvent captures the carbon then passes the cleaned exhaust to atmosphere. In port this solvent is then heated to release the carbon bi-product and stored. Recently this carbon bi-product has been found to create Oxalic acid used to process rare earth metals. A win win all around. 

Rick

Flatlander wrote on May 3^rd, 2026 at 4:25pm:


Exactly. Most often used combo in RFBR match barrels.
RB with a quality bronze brush.

marlinguy wrote on May 2^nd, 2026 at 10:42am:


I have a rifle that does the same exact thing......

Update,

Starting with a clean throat, after firing 60+ rounds in a match yesterday, the carbon ring was clearly back when using a borescope.  Instead of using Bar Keepers Friend (BKF), I used a tight patch soaked with Bore Tech’s C4 positioned at the ring.  Most of the carbon was removed within 30 minutes.  After 45 minutes all the carbon was gone.  Since I plan to remove the carbon after each match, I will go back to using C4.  

For those of you that never clean your 22 rifle bore or wait after several matches to do so, it will require a lot of soaking and scrubbing with C4 to remove the built-up carbon ring.  In that case Bar Keepers Friend may be the answer.

BTW, the carbon ring may not affect accuracy after a match or two or three, but it's a well-known documented fact that it will eventually as the carbon builds up & squeezes the bullet down as it passes through the ring.

Wayne