Carbon ring possible problem? Help please

[Munchigan]

So I need some advice with a problem I’m having with my rifle. Problem is erratic accuracy and some heavy bolt lift and marks on the bullet suggesting that I have carbon buildup. I have a bore scope and definitely tell where the scuffs are coming from right past the neck in the freebore. I have cleaned and even polished this area with bore paste and all is well for about 10 shots then the carbon is back and accuracy becomes erratic again. Rifle is a custom 700 6.5x47 Bartlein 5r I’ve been struggling with this problem since I had it built im not confident in the builder for help anymore so I need some advice on what I should do now. Why is the carbon building up so fast, maby the free boar is too tight? Groups are .25 to .40 for the first 10 shots sometimes more then they start to open up to around .75 or more. the marks become more noticeable you can feel some friction chambering a round and the bolt lift starts to get heavy so I know it causing pressure spikes. Any suggestions appreciated

 

[1911nut]

i check my chamber length with the “plug” tool that fits in the case mouth and compare to my case length. I’m thinkin your chamber is longer than your cases by too much. That’s all I got

 

[1911nut]

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[DShortt]

Post photos. Only way to help you determine if you're getting all the carbon out. Based on your description, I'd say you are not.

 

[jackieschmidt]

i check my chamber length with the “plug” tool that fits in the case mouth and compare to my case length. I’m thinkin your chamber is longer than your cases by too much. That’s all I got

I use these.
I make one for each reamer. Thes are 6PPC, 6BRA, 30BR

 

[Munchigan]

I haven’t thought about my case length to chamber measurement and really didn’t know that a short case could cause carbon buildup in the free bore so this could be the culprit. I’ll try and get some pics up tomorrow to help clarify

 

[DaveTooley]

Sounds like the FB may be too tight. I don't like the +.0005" FB's for this and other reasons.

 

[AlNyhus]

Dave, have you had any success with opening the free bore section up on an already chambered barrel?

 

[DaveTooley]

Al, I have using throating reamers but because of the small amount of metal removed it's more art than science. You always end up with a longer FB. A borescope and no caffeine helps.

 

[Munchigan]

The reamer I bought was ptg T10181 grizzly international .295nk and .167fb length but I have no idea about the free bore diameter

 

[Munchigan]

 

[AlNyhus]

Ouch.

 

[Munchigan]

View attachment 1528468View attachment 1528469View attachment 1528470View attachment 1528471

First picture is clean then 10 to 15 rounds and the picture of the copper is from chambering and round and removing to check for scuffs on bullet

 

[Michael Huebner]

First picture is clean then 10 to 15 rounds and the picture of the copper is from chambering and round and removing to check for scuffs on bullet

The free bore & lead looks really rough to me, lots of tooling marks.
You should clean it real good, even better than your photo and do a chamber cast (cerrosafe) and measure what it is just in front of the neck.
Then measure your loaded round just in front of the neck.
And if you can get the reamer print and see what it is supposed to actually be.
Maybe the reamer is not right and you’re wasting your good barrel.

Cheers
Michael

 

[DShortt]

The second picture shows considerable carbon fouling. The 3rd picture shows considerable copper fouling.
Something is definitely rotten in Denmark.
If all of this is happening in 10-15 rounds then I must say it's far worse than anything I've ever seen by far.
Time to throughly clean and do a chamber cast and measure EVERYTHING.
Your freebore diameter is way out of specs or your powder fouls like mad or something.
Wow.

 

[jelenko]

If I've got it right, the copper in the pic in post 11 came from just chambering then ejecting the unfired round. If that's correct, what looks to me like the end of the chamber is too small.

 

[Munchigan]

Yes thats correct just chambered then ejected not fired and only after it’s been shot some is when the copper being rubbed off. It chambers without rubbing when it’s clean.

 

[DaveTooley]

FB TOO TIGHT.
It needs a throating reamer run in to open it up.

 

[Pres100]

Interesting ... the marks own the chambered round appear to be happening on part of the ogive where there bullet isn't even up to a bore diameter

 

[AlNyhus]

FB TOO TIGHT.
It needs a throating reamer run in to open it up.

This ^^^^^^^