MR2000 and carbon rings

[jelenko]

Has anyone noticed that MR2000 creates carbon rings faster than other powders?

The reason I'm asking is in the last 4 barrels [223 Wylde] the groups have opened up to over 2" at 100 yards at 2000 +/- rounds. I've used MR2000 for most of the rounds down these barrels.

The four barrels were 2 McGowan, 1 Shilen and 1 Criterion.

Thanks

 

[CharlieNC]

That many rounds could have significant throat erosion, check the jamb length.

 

[jelenko]

Yeah. This happening with mag length rounds in an AR15.

The time period for these 4 barrels is coincident with my starting to use a borescope.
When groups opened up on the first barrel I noticed there was a lot of carbon in the throat and almost a ring of carbon - but not solid all the way around. I used Iosso to reduce the amount of carbon in the throat, but after cleaning, accuracy did not come back.
Since then, I've been more aggressive in keeping the throat mostly clean [trying to limit the usage of abrasives].
I'm wondering if, net, it's my use of abrasives, in response to carbon build up, that's causing the earlier than expected loss of accuracy.

 

[SeabeeKen]

Depends on the abrasive. JB, KG2 bore polish, iosso and others will not harm the bore. They are non embedding. You said you removed most of the carbon. Have you removed it all to bare metal? Id remove all carbon and copper and then try again. Is the bore fire cracked? Can you post a pic of throat? A soaking with Bore Tech C4 carbon remover might help.

 

[jelenko]

JB, KG2 bore polish, iosso and others will not harm the bore

Hmmm. I thought some of the other experienced shooters had expressed concerns about premature aging with lots of usage of these- no?

If they really don't damage/accelerate wear, I'm good to go.

On the most recent barrel, I had just Iossoed/FreeAlled it to bare metal. At the range today, same 2+ MOA groups. A new barrel on a different upper produced the 1/2 MOA groups I'm used to with the loads used.

At the same time, as I started to disassemble the misbehaving upper this evening, the screws on sight rail seemed not as tight as I would have thought. So, I've tightened them up and plan to give it another chance tomorrow.
I'll post a pic of what it looks like after putting 50 rounds through if after getting it to bare metal.
001 is ~ 1 inch in; 002 is the start of the throat [kinda obvious] and 003 is ~ 2 inch in.

ETA: Well, 002 seems to be 'broken'. Won't show after attaching it. Key thing about the start of the throat is it looks about the same and with no carbon ring.

EETA: Those pics look better than viewed directly on the phone. In the borescope, the gooves appear darker near where the lands start; i.e., the middle third of the gooves appear shiny, the outside thirds are darker than showing in the pics.

EEETA: I just check the shot log, the barrel in the pics has 1389 rounds through it. Does it look it?

 

[SeabeeKen]

Doesnt look bad from the pics. Pretty good considering the number of rounds. How does it look at the gas port? My AR port was heavily eroded at the port and rifle lost a lot of accuracy. It was shaving off jacket material. I use KG-2 in my match barrels if I get tough carbon but thats rare. I normally use Flitz bore cleaner and it cleans well for me as does Bore Tech. Everyone has their personal favorite. One reason I chose KG2 over JB is that JB is like a grease and difficult to clean out and KG is liquid and cleans out with less mess. Carbon rings are just a fact of life but some powders seem worse than others. Loose sights will certainly cause the issue. I'd check the gas port in the bore also, it could be affect the bullet. Hopefully its just the loose sights. Keep us posted on this, it may help others.

 

[AckleymanII]

Penetrating oil, "Free All" can help loosen up the carbon, especially if you push a couple of patches though the barrel when you are done shooting. Free All is a 21st century penetrating oil...like no other.

Try some Montana Extreme copper cream, then some Flitz bore cleaner, both of which are easier to use than JB.

One main issue I have had over the years, that I recently discovered, was using the bronze bristle brush too long. Figure 50 strokes, put on a new brush.. Also, the use of FINE bronze wool wrapped in that brush with 50 strokes on it, cleans the carbon out very, very well. The Fine bronze wool does not scratch my fine SS Match grade barrels as witnessed in the Hawkeye and Teslong bore scopes! I can not stress this enough!

I was having one heck of a time with R#15, 8208, Varget in my 308 Krieger, it was taking around 100 rounds where the accuracy Where accuracy was ruined, from a 1/4" group barrel.

When you are seeing that Grey carbon start to accumulate, suspect your brush first thing. Try an experiment, mic a new brush, re measure it every 15 strokes, get ready for a shock. Those bristles have to have "spring" in them to scrub the bore.

I use the Copper cream and Flitz bore cleaner on patches, two or three patches, short stroking usually does the job.

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When you get down to carbon starting to accumulate, time to try a new technique/chemicals.

 

[SeabeeKen]

Never tried Free all. ordered a can to test. I tested dozens of cleaners and lubes the last 2 years. Few got past the hype.

 

[jelenko]

Penetrating oil, "Free All" can help loosen up the carbon, especially if you push a couple of patches though the barrel when you are done shooting. Free All is a 21st century penetrating oil...like no other.

Try some Montana Extreme copper cream, then some Flitz bore cleaner, both of which are easier to use than JB.

One main issue I have had over the years, that I recently discovered, was using the bronze bristle brush too long. Figure 50 strokes, put on a new brush.. Also, the use of FINE bronze wool wrapped in that brush with 50 strokes on it, cleans the carbon out very, very well. The Fine bronze wool does not scratch my fine SS Match grade barrels as witnessed in the Hawkeye and Teslong bore scopes! I can not stress this enough!

I was having one heck of a time with R#15, 8208, Varget in my 308 Krieger, it was taking around 100 rounds where the accuracy Where accuracy was ruined, from a 1/4" group barrel.

When you are seeing that Grey carbon start to accumulate, suspect your brush first thing. Try an experiment, mic a new brush, re measure it every 15 strokes, get ready for a shock. Those bristles have to have "spring" in them to scrub the bore.

I use the Copper cream and Flitz bore cleaner on patches, two or three patches, short stroking usually does the job.

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When you get down to carbon starting to accumulate, time to try a new technique/chemicals.

Thanks!
I've been using FreeAll for a couple weeks and bronze wool for the past week.

When I tried Flitz the bore cleaner, it seemed to work about the same as Iosso but was a bit messier to use.

 

[jelenko]

Well, after tightening the sight base, didn't make any difference.
Very odd. The groups opened up ~ 1000 rounds. Before going south, just a few hundred rounds earlier, had a couple < .5 MOA groups.

I took along another upper with a new barrel just to confirm it wasn't me doing the group opening.

It may just be a coincidence, but this is the third Criterion that I've had a problem with.
The first was a nutted prefit on a Pierce action in an Eliseo chassis. Couldn't get it to group; sent back to Criterion, they sent a replacement. The replacement shot bug holes for over a 1000 rounds but opened up shy of 2000. This one also shot bug holes for almost a 1000 rounds; then, didn't.

 

[Djfergus]

Som

Has anyone noticed that MR2000 creates carbon rings faster than other powders?

The reason I'm asking is in the last 4 barrels [223 Wylde] the groups have opened up to over 2" at 100 yards at 2000 +/- rounds. I've used MR2000 for most of the rounds down these barrels.

The four barrels were 2 McGowan, 1 Shilen and 1 Criterion.

Thanks

I know of the big overbore cartridges will carbon up in as few as 30 rounds. To the point that pressure is erratic in 30 rounds. I do believe there is something going on with those circumstances because not all of those same cartridges will carbon up that quickly in other rifles....even with same powders being burned.

 

[BlackGrouper]

What load are you using, mag length/single loading ect.?

 

[jelenko]

25,8 MR2000, H75's, mag length. Running both rapid fire and single load strings. Rapid fire = 10 shots in 60 seconds.

 

[BlackGrouper]

I'd try a different load like the standard 77 Matchking 23.8gn Reloder 15, 24gn Varget ect. to see if the barrel is still capable of accuracy.
Have had a couple button rifled barrels hammer with a load when new then scatter, as the throat wore. Switching load usually cured the problem.

 

[AckleymanII]

Jelenko, I would have the bore dia at the muzzle checked against the throat dia.

Also, velocity when the barrel was new vs what it doing now with the same load.

 

[jelenko]

I'd try a different load like the standard 77 Matchking 23.8gn Reloder 15, 24gn Varget ect. to see if the barrel is still capable of accuracy.
Have had a couple button rifled barrels hammer with a load when new then scatter, as the throat wore. Switching load usually cured the problem.

Would changing the seating depth on the currrent load do the same?

 

[pdhntr]

.... Rapid fire = 10 shots in 60 seconds.

Looking carefully at the pics, I can see significant fire cracking.

I am no stranger to this as it happens to my pd rifles.

Did you take a COL measurement when the barrel was new so you can monitor the throat erosion?

Jim

 

[jelenko]

Jelenko, I would have the bore dia at the muzzle checked against the throat dia.

Also, velocity when the barrel was new vs what it doing now with the same load.

So, this got me to thinking about throat erosion. Just due to what I've been working on I hadn't taken distance to lands measurements on this barrel when it was new.
Comparing now with a new barrel chambered by the same smith, it appears the throat has eroded 85 thousandths! That's just over 8 thousandths per 100 rounds!
I did check the muzzle at 5X - looks very sharp.

 

[jelenko]

Looking carefully at the pics, I can see significant fire cracking.

I am no stranger to this as it happens to my pd rifles.

Did you take a COL measurement when the barrel was new so you can monitor the throat erosion?

Jim

Jim - See the post I just made. The fire cracking does look like more than 1000 rounds.
At this point, I'm thinking I must have put more 'rapid fire' [10 rounds in 60 secs] rounds through it than usual. From the measuring I and others have done for 223, erosion runs 2 to 4 thousandths per 100 rounds. Of course, a big factor is % of rapid fire. There are times when I'm working on something that I'll go through 4 strings of 10 shots in 10-15 minutes. The barrel gets quite hot doing this.

I'm completely ok if the loss in accuracy is due to erosion - it's what happens to the barrel when it's used.

 

[AckleymanII]

Ok, good to know. Rapid fire maybe taking more of a bite of the throat than you are aware. Length is one issue, dia of the throat from flame temp is another.

High quality barrels will usually have the same dia at the muzzle as they do at the breach when new, usually. Worst case, they are close. If your throat dia has opened up .0008, this is another issue.

Your gunsmith can usually help you with this dia issue.

Due to your application, it maybe worth investing in one of Bartline's barrels that are less resistant to wear, at least worth a thought anyway.

This is an illustration of the throat wear in a 6 BRA where the muzzle dia is .236

Muzzle dia, threads are for a muzzle break:


At 1200 rounds, look how the bore dia in the throat has been enlarged, throat dia started off at .236 with H4895 being the only powder fired in the barrel. NOTE: THROAT DIA HAS OPENED UP .0022 SINCE NEW!!!