Carbon Ring Removal?

[deertroy1]

What's the best method for removing a stubborn carbon ring. I purchased a new to me Cooper in 6mm Rem and apparently the previous owner/owners neglected it. I tried RG-1 and JB-Bore Paste used on a patch around a nylon brush while short stroking the first 6" of the bore. I was then able to seat bullets to the lands but after about 10 rounds I measure the COL and it is 0.070" less than it was after cleaning. This leads me to believe I'm only knocking the top off of the carbon ring, just enough to let the bullet reach the lands.
The rifle shows signs of pressure a grain or so above published starting loads. I tried a couple different powders and same thing. Velocities however are close to starting load velocities (Oehler 35). Thus I suspected a carbon ring (still waiting for borescope to confirm).

Example:
Hodgdon starting load 24" 40gr IMR 4064 Sierra Bullet = 3355 fps

My load 24" 40.5gr IMR 4064 Sierra 70gr Bullet = 3262 fps shows ejector mark

Same load in my 22" McGowen barrelled Savage was able to reach Hodgdon max of 44.5gr and over 3600 fps no signs of pressure. Same components, same brass. Savage has a slightly longer throat but both loads are nowhere near the lands.

Benchmark barrels has a method that involves using Simichrome but that is difficult to get here in Canada, at least at a reasonable price! I have Flitz but have read you can ruin your barrel by actually polishing the bore!

 

[JMW67]

bronze brush on a short section of cleaning rod and a cordless drill used with boretech carbon remover is how I have gotten the bad ones out work just the area of the ring at low rpm keeping it wet with the carbon remover

 

[tobnpr]

You should be able to clearly see carbon ring- if present- without a borescope, just shine a light down the bore.
I like Sharp Shoot-R products- including their Carb-Out.
If it still persists JB Bore Paste.

 

[deertroy1]

You should be able to clearly see carbon ring- if present- without a borescope, just shine a light down the bore.
I like Sharp Shoot-R products- including their Carb-Out.
If it still persists JB Bore Paste.

What else would cause my COL to shorten by 0.070" after 10 or so rounds.
I tried JB-Bore Paste. Barely touched it.

 

[cape cove]

Had a carbon ring in my 6mm BR. I took a patch and soaked it with Bore Tec Carbon remover and placed it in the chamber against the carbon ring and left it for a few hours. Then I soaked an oversized bronze brush on a short rod and put it in a drill and turned it at a medium rate for a while where the ring was then cleaned patched it. Done this a few times and the ring was gone.

 

[tobnpr]

What else would cause my COL to shorten by 0.070" after 10 or so rounds.

Sounds odd.
Explain more how you determined this.
You're measuring COAL (not OAL) using a comparator?
You loaded ten rounds, shot them- then measured again, using the comparator? Or did you have resistance chambering the rounds loaded to the original length?

Walk through exactly what you did.

 

[Painless300]

CLR from any Walmart or grocery store will work very well on carbon rings. I run it on a wet patch let it soak for a 15 mins then scrub with copper brush. Patch it out then repeat if necessary until it gone.

 

[deertroy1]

Sounds odd.
Explain more how you determined this.
You're measuring COAL (not OAL) using a comparator?
You loaded ten rounds, shot them- then measured again, using the comparator? Or did you have resistance chambering the rounds loaded to the original length?

Walk through exactly what you did.

Measuring bullet to lands using a comparator? Measured 2.930". Seat bullets to 2.820" (mag length). Fired 10 rounds. Checked length again using comparator = 2.856". Cleaned barrel thoroughly checked again 2.930" to lands.

 

[deertroy1]

So, as I suspected, it looks like I have a carbon ring. I'll let others chime in but here's the video from the borescope!

 

[LaHunter]

Yep, I would say you have a carbon ring. It may take some extended 'soak time' with something like Boretech's carbon remover to get it fully removed.

 

[tobnpr]

As I look at your picture, I believe what I'm seeing is carbon buildup in the neck of the chamber- which is different than what we usually refer to as "carbon ring" in the throat.

Your buildup is is behind the neck/leade junction. To save myself a ton of typing, Boyd Allen has a good writeup on this in Accurate Shooter below. Ten rounds is absolutely nuts for this to be occurring, I've never heard of it building up that quickly. Keep in mind, you can't use a bore guide when trying to remove- this is in the chamber.

"The thing that happens at the end of the neck part of the chamber is real, but I believe that there is some confusion on the terminology, or perhaps there is a need for some clarification. The material in that area is simply powder fouling that stacks up (more or less depending on the powder)in an area where "normal" cleaning methods may not be effective in removing it. As the poster stated, it can be a problem, and should be dealt with in normal cleaning. One thing that was not mentioned is that if cases of different lengths are used, powder fouling left from the use of the shorter cases, can impinge on the mouths of longer cases, affecting consistency of bullet release. Getting past that for a moment, the other area that needs to be mentioned is the build up of what is generally referred to as hard carbon. This material is powder fouling on steroids that has been transformed by pressure into something that cannot be removed by any chemical or brush. It can be seen right where the freebore starts, at the top of the chamfer at the end of the neck part of the chamfer, very slightly down the barrel from the powder fouling buildup that was previously described. It can also be found in the back end of the bore, usually in the back third or so of the barrel. Various procedures involving the use of IOSSO are the most effective means of removing these deposits. I use a method that I learned by reading how Tony Boyer did is back in the late 90s, and have not changed it. More recently the manufacturer has a different set of instructions. I assume that they work as well. Some powders such as 133 do not have this problem.Others do, to the extent that for types of shooting that involve extended strings between cleaning, such as varmint shooting, that this may be a major factor in powder selection. One example would be using VV 140 in the .204 Ruger. Shooters have found that the hard carbon buildup was so fast and extensive that a change in powder was required. A middle ground powder may require treatment every hundred rounds or so to stay ahead of the problem. None of this can be properly evaluated without the use of a bore scope, except to say that I did this and the problem went away."

 

[deertroy1]

As I look at your picture, I believe what I'm seeing is carbon buildup in the neck of the chamber- which is different than what we usually refer to as "carbon ring" in the throat.

Your buildup is is behind the neck/leade junction. To save myself a ton of typing, Boyd Allen has a good writeup on this in Accurate Shooter below. Ten rounds is absolutely nuts for this to be occurring, I've never heard of it building up that quickly. Keep in mind, you can't use a bore guide when trying to remove- this is in the chamber.

"The thing that happens at the end of the neck part of the chamber is real, but I believe that there is some confusion on the terminology, or perhaps there is a need for some clarification. The material in that area is simply powder fouling that stacks up (more or less depending on the powder)in an area where "normal" cleaning methods may not be effective in removing it. As the poster stated, it can be a problem, and should be dealt with in normal cleaning. One thing that was not mentioned is that if cases of different lengths are used, powder fouling left from the use of the shorter cases, can impinge on the mouths of longer cases, affecting consistency of bullet release. Getting past that for a moment, the other area that needs to be mentioned is the build up of what is generally referred to as hard carbon. This material is powder fouling on steroids that has been transformed by pressure into something that cannot be removed by any chemical or brush. It can be seen right where the freebore starts, at the top of the chamfer at the end of the neck part of the chamfer, very slightly down the barrel from the powder fouling buildup that was previously described. It can also be found in the back end of the bore, usually in the back third or so of the barrel. Various procedures involving the use of IOSSO are the most effective means of removing these deposits. I use a method that I learned by reading how Tony Boyer did is back in the late 90s, and have not changed it. More recently the manufacturer has a different set of instructions. I assume that they work as well. Some powders such as 133 do not have this problem.Others do, to the extent that for types of shooting that involve extended strings between cleaning, such as varmint shooting, that this may be a major factor in powder selection. One example would be using VV 140 in the .204 Ruger. Shooters have found that the hard carbon buildup was so fast and extensive that a change in powder was required. A middle ground powder may require treatment every hundred rounds or so to stay ahead of the problem. None of this can be properly evaluated without the use of a bore scope, except to say that I did this and the problem went away."

So do you think this could cause my loads to show pressure well below max.?

 

[deertroy1]

Seems this guy had the exact same problem? Turned out not to be a carbon ring!
Problem
Solution

 

[Dosh]

Perhaps try IOSSO bore paste.