Carbon donut

[Jase PTRC]

I had this trouble when i started a new batch of bergers when i first started reloading, it turned out that the newer batch of projectiles were substantially longer base to ogive than the previous. Even though i was measuring with a comparator to the same length as my previous lot. I also realised my Hornady Comparator was also measuring further up towards the tip of the projectile than where the actual ogive was. After having this issue i went back and got my modified case out and re checked this new batch i ended with a measurement that was .030 different to the previous batch causing me to go from .010 jump to .020 jam. So the actual shape of the ogive was considerably different and caused me the problem. Needless to say i now check every new batch in with the modified case.

[KHGS]

http://forum.accurateshooter.com/threads/the-carbon-ring.3772542/

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 ?

The post at the link above explains the carbon ring formation exactly. SAMI spec reamers USUALLY cut the neck up to .030" longer than trim length & this is where the carbon ring forms.
Keith H.

[Frank Green]

I'm going to say no to the carbon ring causing the problem. 2208 is Varget correct? It's all I run in my .308 win. guns with no issues as well as some other calibers.

I'd like ya to find out the exact chamber reamer used. Get a print or drawing of the chamber reamer if you can. The first thing that goes on a chamber reamer is the throat as this is cutting all the time even if you use a roughing reamer. When it goes it will start cutting undersize. You could have one problem making another problem appear etc...

I'm curious.

Later, Frank
Bartlein Barrels

[MR.Sako]

well i figured out my problem. car polish. i must have slipped when adding polish to my tumbler media resulting in a build up in the necks. i dropped a bushing size and put the expander ball on which scraped out all the build up in the neck, i also threw out the media so this would never happen again.

thanks all

[Brad Y]

No need to add polish to a media. Who knows what residue might do to powder and what it produces when it burns. And if it could cause a reaction with copper jacket too... whole new can of worms.

[Frank Green]

well i figured out my problem. car polish. i must have slipped when adding polish to my tumbler media resulting in a build up in the necks. i dropped a bushing size and put the expander ball on which scraped out all the build up in the neck, i also threw out the media so this would never happen again.

thanks all

Thanks for posting and keeping us up to date. I've been wondering what was going on with this.

Later, Frank
Bartlein Barrels