Is carbon ring theory a myth? Let’s try prove / disprove

I had a friend call me from the range one day for help. His mom brought her Ruger sp101 and wanted to try a few magnums through it. Previously she had only ever shot 38 special in it. They couldn’t get a magnum round to chamber. I told him to get a 40 or 45 cal bore brush and clean the charge holes well and then they were able to load magnum rounds. I have no idea how many 38s went through it before they gunked it up enough to prevent magnums from chambering fully. Never heard of anyone having an overpressure situation before.

CraigC said:

The over-pressure condition is caused when the crimp can't open, because it has nowhere to go.

Click to expand...

@CraigC has identified the source of the concern. An example from an obsolete rifle cartridge is the French 8x50R (the first smokeless round). It was first designed as the ‘Balle D’ but was revised prior to WW 2 (I think) to function better ballistically I believe in machine guns. The redesign, for what ever reason, changed the location of the largest diameter of the projectile from outside the case to inside the case. All French firearms in 8x50R were modified by opening up the chamber enough to allow the brass to open up enough to release the projectile without additional pressure.

That being said the ‘Carbon Ring’ myth has been around long enough to well pre-date the Internet. I’ve been shooting 38/357 for 40 years and the recommendation existed back then. Back then we called unsubstantiated knowledge ‘Urban Legend’ instead of internet myth.

I can’t help resolve if it is true. I don’t own a test lab and I think a lab would be needed to really answer the question definitively. But, much like many other things in life, it makes sense that there could be a problem. So I heed the advice and keep my 38/357 chambers clean.

That was a lot of words written that didn’t really address/answer your question. You all have my permission to do as my wife does. Ignore me

What baffles me is how anyone could let a gun get dirty enough for this to become an issue.

But! I have seen people with .357 magnum revolvers that would not chamber a .357 due to crud buildup. I have seen people force .357 rounds into the chambers so they could shoot them, but none of them have ever said:
“Wow! That has a lot more kick than it did before.” OR “Something is wrong. There seemed to be more (kick - flash - boom...whatever)”
My theory on why?
Because they don’t shoot enough .357 to know if they have an over pressure situation or not.

Any build up large enough to cause a pressure spike would cause a failure to chamber. I just don't think it's possible. It's a Catch 22.

It's like dogs. There are no bad dogs. Just bad dog owners. Some shooters neglect to clean their weapons in a timely and/or adequate manner. Then go on the internet with their "discovery".

I don't always clean every session, sometimes I skip one with the stainless guns. But they'll get cleaned at least every 500 rounds or so at the most. I've never experienced a buildup large enough to prevent chambering of a .357 round. I check for it all the time just out of curiosity. I keep a dummy .357 round in my cleaning box. I shoot exclusively cast bullets.

I clean my chambers with a .375 rifle brush which is just the right diameter. Not so big it takes excessive force but still make good contact with the chamber walls, does not wear out rapidly, and it's much longer than a pistol brush. Three passes per chamber and it's clean.

Pat Riot said:

What baffles me is how anyone could let a gun get dirty enough for this to become an issue.

Click to expand...

Same.

-Stan

What people have to realize is that an FA .454 at 65,000psi is unlike anything else on the market. One of the downsides to such tight tolerances is that there is no "tolerance" for debris. Whether it's trail dust, mud, snow or a carbon ring. Where a S&W or Ruger can run fine with some mud in the action, 10,000rds worth of carbon build-up or 10yrs worth of pocket lint, the FA will often not. Freedom Arms is also unlike 99% of other manufacturers in that they not only condone handloading but even go so far as to provide loading data. Somehow I doubt that the warning about shooting .45Colt out of their .454's is a marketing ploy.

JohnKSa said:

Whether it does or doesn't, it does seem that the claims about it are related to only one particular chambering combination and therefore would need to be either proved or disproved using only that particular chambering combination.

In other words, if this is all about FA claiming that carbon rings from .45Colt can blow a .454Casull, then testing/experience with .38/.357 or .22S/.22LR or .32S&W/.32H&RMag/.327Mag, etc. doesn't really prove or disprove anything.

Click to expand...

Exactly. It's only a "myth" as it pertains to other guns in other chamberings. How people misconstrued one to mean the other is beyond me.

Pat Riot said:

What baffles me is how anyone could let a gun get dirty enough for this to become an issue.

Click to expand...

In an FA, the only place where this applies, it doesn't take much. Especially if you're shooting cast bullets.

CraigC said:

What people have to realize is that an FA .454 at 65,000psi is unlike anything else on the market.

Click to expand...

Newton's Law attaches, I don't think I'm interested in setting one of those off. lol

You'll know you have a problem when you have difficulty seating cartridges in the chamber. As I said, it's more an inconvenience than anything.

Here's a more extreme example of not cleaning a gun. Just the other day a friend said he hasn't cleaned his SW 19 since nineteen ninety-something, has fired mostly 38. It continued to fire/eject 38 brass just fine. Then he moved to 357...chambered/fired but would not extract at all. No surprise. It required a solvent drip/dwell in each charge hole. Not sure if he had resistance chambering the 357 brass but that would certainly be a reminder to clean yesterday. His home defense gun turned paper-weight.

Other than being a inconvenience when having to clean the “ring” out of my revolvers there are a whole lot more important things I have to worry about these days at my age.

I cannot say that I have ever had 357 Magnum chambering problems in my S&W Model 19 after shooting 38 Special ammunition in it. But, I do keep it clean.

When I started getting some revolvers chambered in 38 Special, I saved the 38 Special cases for those revolvers and only shot ammunition in 357 Magnum cases in my 357 Magnum revolvers.

Since I reload, I can tailor the ammunition to anything I want within limits of the performance specifications for each cartridge.

As I have expanded into 32 caliber and 44 caliber revolvers as well a 460 S&W Magnum revolver, I only shoot ammunition loaded in cases that the revolver is chambered for. Easy for 32 SWL, 32 H&R, 327 Fed Mag, 44 Special and 44 Magnum as lots of data is available, but it took a while to find a light load for the 460 S&W Magnum case.

I recently obtained a S&W 610 (10mm) revolver. I've plans top consume some 40 S&W ammunition in it during the next time I take it out just to use it up, but after that one session, I'll only shoot ammunition loaded in 10mm cases. (In part, it is an experiment with different brands of moon clips. The 10mm cases and 40 S&W cases I have work differently in the different brands of moon clips I have for the revolver).

Bottom line though, one needs to clean their revolvers once in a while.

I presume that shooting dirty ammo causes the problem quicker than clean ammo as well.

SteadyD said:

I presume that shooting dirty ammo causes the problem quicker than clean ammo as well.

Click to expand...

Dirty ammo, waxy lube on the bullet/residue on brass, incomplete/poor ignition, light charge.

Ru4real said:

A revolver carbon ring is supposed to “sneak up” and cause a pressure spike. Revolver, 38 special shot in 357 Mag and then the shooter switches to 357 Mag, carbon ring, pressure spike. Or 44 special 44 Mag. Or 45 Colt 460 S&W. Etc.

The extracted cases always have straight, smooth sidewalls.

Maybe it is possible to see after thousands of rounds, no cleaning?

Proof of carbon ring pinching should be seen in slight bottle neck appearance in fired cases, I think.

How many rounds have you fired, what gun, caliber, such that the longer cartridge would no longer just drop in?

Have you seen fired cases that have a bottle neck shape due to the carbon ring?

Click to expand...

The extracted cases appear to have straight, smooth sidewalls.
I really doubt you can visually discern any deformation.
A micrometer or digital caliper may show it.
At any rate, without the proper test equipment & a proper test method, there's no way to prove one way or another if this is fact or myth.

Pat Riot said:

What baffles me is how anyone could let a gun get dirty enough for this to become an issue.

Click to expand...

As the two posts right before me here say - "Dirty" ammo desn't need a whole lot of rounds through the gun to form a crud ring.
My swaged lead, wax type lubed .358" diameter slugs that sit on top of a pinch of Unique leave a read hard ring - real quick.

Myth to some/real to others

It's easy enough to prove, what your looking at is the ability of the case to be able to expand enough to release the bullet. The smaller the window of expansion, the more the short start pressure of the load increases.

Take a .358" bullet and load up 6 rounds using a powder like ww-231, unique, AA#5,etc. Nothing hot & use a load that's in the middle of the reloading data. Take the same bullet but size them to .360"/.361" and use the same load. Go out & do some testing you'll find out real fast if it's fact or fiction.

I swage my own jacketed 44cal bullets. I make them .430" for a s&w 629 and ..432" for a contender. Was doing test loads with both firearms during the same range session. Had the same loads just different diameter bullets for each firearm. At the end of the session I had several sighter/bbl fouling rounds for the contender left. I like shoot a couple fouling shots in a clean bbl then test loads. Anyway I put a cylinder full of those mild/middle of the road fouling rounds with the .432" bullets in the s&w 629.

They all went bang, nothing odd like extremely loud noises/flash/etc. It got interesting when I tried to eject the cases, had to pound them out with a hammer and brass rod. They blammo ammo/fouling loads were 1 1/2gr less then the loads I just tested with the .430" bullets. Those hotter loads with the .430" bullets had no problem ejecting. The .432" bullets with the lighter load did.

.432" bullet 8.0gr of universal
.430" bullet 9.5gr of universal

I was testing what the bullet would do expansion wise in a given velocity window. A 1100fps+/- impact was what I was testing. Mild loads @ 25yds do the same thing as hot loads that slow down @ 100yds, hence +/- 1100fps.


The home swaged bullets I was testing


Everything is a myth until you have to break out the hammer

Ru4real said:

I did some limited testing, proving to me, the carbon ring pressure spike is a myth. No one has posted a picture of a straight wall pistol case with a slight bottle neck proving a carbon ring was thick enough to possibly inhibit bullet release.

Click to expand...

You've proven nothing. As it pertains to .357's and .44's, it ain't a myth because it never should've been applied to those guns. File that under misinformation/misconception/ignorance.

If you were going to prove it a myth, you'd have to shoot an FA .454 dirty with .45Colt, then force a 65,000psi .454 cartridge into the chamber and fire it without a catastrophic failure. I know of no one with an FA .454 willing to do that. To call it a myth is irresponsible.

I don't need a picture of a blown up sixgun to take the manufacturer's warnings to heart. It applies nowhere else.

What's a spare cylinder sell for from Freedom Arms?
Here's the $25 solution to Freedom Arms' issues.

https://www.longhunt.com/storelh/index.php?route=product/product&path=88_89&product_id=320

Available for 38/357, .45, and .44.


A tool to CLEAN and RESTORE .357, .45, and 44mag Chambers


Remove carbon and lead fouling in .357,.45, and 44 mag chambers.


This tool safely removes carbon and lead that collects in the chambers and cylinder throats of revolvers and rifles.

Cleaning regularly will significantly reduce throat erosion and restores the cylinders and chambers to SAAMI specifications.

Easy breech access to clean rifle chambers. Adapted to fit standard 8-32 cleaning rods.

Absolutely no impact on your present chamber dimensions.

Ru4real said:

We are probably saying the same thing.

I believe misinformation/misconception/ignorance creates myths, don’t you also?

Click to expand...

Not really. Myths are borne out of explanations for what people believe is the inexplicable. This is just information taken out of context by people who don't know any better.