Carbon donut

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MR.Sako
Posts: 29
Joined: Mon May 23, 2016 7:19 am
Location: Grafton Rifle Club

Carbon donut

#1 Postby MR.Sako » Sat Oct 21, 2017 9:58 pm

Hello everyone
last week i had some trouble chambering a round on my 7th or 8th shot in my second stage, upon inspection there were marks engraved on the projectile and a carbon ring just in front of where the case mouth sits in the chamber, which shocked me because i scrubed it clean the day before.

when i got home i scrubbed it clean once again using jb in the throat and got it spotless, i verified using a bore scope and it was bare metal.

today on a totally clean barrel using the same load as before i had a practice shoot at 100 yards firing 11 shots with no issues but at the 400 yard mound halfway during my first stage it had trouble chambering a round once again with the same scoring around the projectile as before which has left me stumped as to how quick the donut is forming. i dont mind cleaning but the donut is forming far to fast. any one have any ideas?
some info on the rifle
barnard action
bartlein light palma barrel 11 twist chambered in .308 throated for hbc's done about 1150 rounds
my load is 46.4 grains of 2208
lapua brass
federal gold medal match large rifle primer
155 gr hbc 15 thou jump
tl;dr
carbon ring forming extremely fast need some help getting it under control
thanks all
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john h
Posts: 1
Joined: Tue Aug 01, 2017 1:45 pm

Re: Carbon donut

#2 Postby john h » Sat Oct 21, 2017 10:28 pm

personal preference but i always found 2208 dirty and 2206H a lot cleaner in my rifle

Pommy Chris
Posts: 168
Joined: Tue Oct 21, 2014 12:05 pm

Re: Carbon donut

#3 Postby Pommy Chris » Sat Oct 21, 2017 11:23 pm

john h wrote:personal preference but i always found 2208 dirty and 2206H a lot cleaner in my rifle

I can shoot 200 rounds or more with 08 and have no issues. If this issue is happening it is not powder it is something else. resizing, loading or the armourer at fault no way can a carbon ring cause issues that quick something else is wrong.
Chris

Pommy Chris
Posts: 168
Joined: Tue Oct 21, 2014 12:05 pm

Re: Carbon donut

#4 Postby Pommy Chris » Sat Oct 21, 2017 11:30 pm

Do you have an ogive to base measuring tool? If not get one. I measure every round I make/ Also a carbon ring wont stop you chambering a round have you trimmer your brass recently for example something else is going on it is not the carbon.
Chris

Gyro
Posts: 140
Joined: Sat Jun 10, 2017 2:44 pm
Location: New Zealand

Re: Carbon donut

#5 Postby Gyro » Sun Oct 22, 2017 3:16 am

http://forum.accurateshooter.com/thread ... .3772542/j

Have we identified what carbon and where yet lads ??

Mr Boyer's book talks about a carbon ring at the front of the chamber that can be a problem. This build up ( assuming it does exist ) will only be removed properly with a special tool used in a certain way ?

Gyro
Posts: 140
Joined: Sat Jun 10, 2017 2:44 pm
Location: New Zealand

Re: Carbon donut

#6 Postby Gyro » Sun Oct 22, 2017 5:48 am

Boyer's book BTW is very good and explains a lot of shooting details very well. I would totally recommend it.

6.5x55ai
Posts: 141
Joined: Mon Mar 18, 2013 4:21 pm
Location: Waikato NZ (Ex Tyabb)

Re: Carbon donut

#7 Postby 6.5x55ai » Sun Oct 22, 2017 6:07 am

You need to drop the "j" of the end of that link to stop the good old 404 error.

Yes Tony Boyer's book is a gem.

I have used many brands of powders over the years - Norma, VV, Nobels, Alliant, ADI, WW and the only time I got caught out with a carbon ring was several years ago with Winchester 760 in my old 6.5 Swede Ackley. After about 200 shots from new I had resistance chambering the round (at a championship shoot!). Coincidentally the day b4 the shoot my Hawkeye had turned up and I had it with me and “lo and behold wot’s this". Pretty tenacious to remove - short stroke cleaning the JBs. Never had the problem again as I just ensured I paid attention to that part of the chamber on a more regular basis. W760 has a deserved reputation for carbon rings but 2208??

I agree with Pommy Chris, something else may be going on, but cannot offer further constructive comment.

MR.Sako
Posts: 29
Joined: Mon May 23, 2016 7:19 am
Location: Grafton Rifle Club

Re: Carbon donut

#8 Postby MR.Sako » Sun Oct 22, 2017 7:02 am

Pommy Chris wrote:Do you have an ogive to base measuring tool? If not get one. I measure every round I make/ Also a carbon ring wont stop you chambering a round have you trimmer your brass recently for example something else is going on it is not the carbon.
Chris

I measured all my rounds and they are all within a thou of each other and the cases have not grown significantly warrant trimming, i can put an empty case in the chamber and the bolt falls closed so its not fouling on the case but the projectile. I will take a picture of the marks left on the projectile.

MR.Sako
Posts: 29
Joined: Mon May 23, 2016 7:19 am
Location: Grafton Rifle Club

Re: Carbon donut

#9 Postby MR.Sako » Sun Oct 22, 2017 7:30 am

These are the marks being left on the projectile. I colored it in with sharpie so you could see it better.
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Longranger
Posts: 202
Joined: Sat Mar 02, 2013 9:49 pm
Location: Queensland

Re: Carbon donut

#10 Postby Longranger » Sun Oct 22, 2017 3:55 pm

What was the reamer used for that chamber and what freebore?

Looks like a hard jam to me.

MR.Sako
Posts: 29
Joined: Mon May 23, 2016 7:19 am
Location: Grafton Rifle Club

Re: Carbon donut

#11 Postby MR.Sako » Sun Oct 22, 2017 5:17 pm

Longranger wrote:What was the reamer used for that chamber and what freebore?

Looks like a hard jam to me.


im unsure what reamer was used when it was smithed i specified that i would be using hbc projectiles but it looks like it has more freebore and a tighter chamber then a b150

i thought it was a hard jam also but the marks on the bullet are to far down and around the entire circumference and when clean has no effect on closing the bolt

i will have to take some pictures now it clean

Wal86
Posts: 68
Joined: Sun Nov 20, 2016 5:10 pm
Location: Kilmore, VIC

Re: Carbon donut

#12 Postby Wal86 » Sun Oct 22, 2017 5:58 pm

Mr Sako

Have you measured the bearing surface OD of your projectiles . Most throat dia are .30845 (but it depends on your reamer specs) it could be possible that your projectiles are larger in diameter than your throating reamer diameter.
Depending on quality of projectiles some maybe ok others that are larger may not?

I dont believe it's a carbon ring problem

Cheers

Alan

MR.Sako
Posts: 29
Joined: Mon May 23, 2016 7:19 am
Location: Grafton Rifle Club

Re: Carbon donut

#13 Postby MR.Sako » Sun Oct 22, 2017 6:07 pm

Wal86 wrote:Mr Sako

Have you measured the bearing surface OD of your projectiles . Most throat dia are .30845 (but it depends on your reamer specs) it could be possible that your projectiles are larger in diameter..

I dont believe it's a carbon ring problem

Cheers

Alan


Alan
I to thought it had something to do bearing surface diameter but i loaded up a dummy round with a sierra palma and a berger fullbore with the same issue

attached are some pictures of the chamber cleaned

thanks
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Pommy Chris
Posts: 168
Joined: Tue Oct 21, 2014 12:05 pm

Re: Carbon donut

#14 Postby Pommy Chris » Sun Oct 22, 2017 6:21 pm

I would clean the rifle make rounds for a shoot and remove firing pin and chamber every round. Then do your shoot and see what happens. No way is that carbon causing those marks on the projectile.
Chris

MR.Sako
Posts: 29
Joined: Mon May 23, 2016 7:19 am
Location: Grafton Rifle Club

Re: Carbon donut

#15 Postby MR.Sako » Sun Oct 22, 2017 6:40 pm

Pommy Chris wrote:I would clean the rifle make rounds for a shoot and remove firing pin and chamber every round. Then do your shoot and see what happens. No way is that carbon causing those marks on the projectile.
Chris


Its clean now and all 24 round chambered with no markings. Ill see what it does on saturday.


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