Carbon ring?

[STS]

An alternative to the Sinclair gauge, and in your case the need to modify it, is to use one of your cases and cut off half of the neck. Clean up the case and cut off piece and seat a bullet backwards in the case and place the cut piece on the base of the bullet. Make sure the gauge is longer than the reamer print measurement then chamber the test round. The chamber will seat the neck piece or seat the bullet deeper and give you an exact measurement of your chamber length. It's simple to do, works well and costs little. Takes about 5 minutes to do.

 

[fdshuster]

STS: Interesting. How do you make a perfect, square cut when cutting off the front half of the case neck?

Most of us do not have a lathe or other precision cutting tool, and if not square would not the "long" edge make first contact, and not the "short" edge? Just askin about something I never thought to try, but sounds like a good idea.

 

[kelbro]

STS: Interesting. How do you make a perfect, square cut when cutting off the front half of the case neck?

Most of us do not have a lathe or other precision cutting tool, and if not square would not the "long" edge make first contact, and not the "short" edge? Just askin about something I never thought to try, but sounds like a good idea.

It doesn't have to be a perfectly square cut, you are still using the original 'end' of the case. A picture here would explain it better.

 

[fayettefatts]

I made a gauge similar to the one STS made, but used a piece if round plastic instead of a bullet. Works well. I'm sure it's not 100% accurate, but it's real close and repeatable.

I've also read about using an aluminum arrow shaft to scrape out the ring. I had a carbon ring develop in my 6BR last year. Didn't have an arrow shaft, so I ran a piece of 223 brass into a 6BR neck die to push the shoulder way back 'til it had a real long neck (longer than the 6BR by quite a bit). Then I threaded the primer pocket so that it fits on a cleaning rod. After expanding to 6mm and flaring the mouth slightly, I use it to scrape the throat after every couple hundred rounds and haven't had another carbon ring.

 

[fdshuster]

kelbro: Thanks, that explains it. I was not thinking that you would still be using the original case mouth and not the cut edges.

 

[fdshuster]

STS: Your method works fine. I did seat the bullet normally thinking it would give the sliding collar a smoother start and even applied a very minimal coating of oil, more like a drop spread around.

I of course did get a non square cutoff with the Dremel cutoff wheel, but as kelbro said, it does not matter. (Thanks kelbro). It did take me more than 5 minutes, but when I do something like this for the first time I can be a real klutz/ all thumbs, so go extra slow.

It shows a chamber length of 2.1355", and the Sinclair gauge shows 2.137". Close enough to be of no concern. Thanks for the great tip.

 

[STS]

STS: Interesting. How do you make a perfect, square cut when cutting off the front half of the case neck?

Most of us do not have a lathe or other precision cutting tool, and if not square would not the "long" edge make first contact, and not the "short" edge? Just askin about something I never thought to try, but sounds like a good idea.

The existing end of the neck is not disturbed and will still be square. I have a lathe, but to do this procedure I use a dremel abrasive cut off wheel to cut the neck at the half length point. I square up the remaining neck on the case with the case trimmer and smooth out the cut end of the forward section with a little 400 grit paper. Made sure everything is deburred and cleaned up and your good to go. It's easy and gives excellent results.

 

[STS]

FD, your a success! I replied to your question before reading the remainder of the thread. Nice job. One thing to remember is that there is a 45 degree angle transition from neck diameter of the chamber to the throat. The smaller the case neck of your gauge relative to the chamber neck the longer the chamber will measure. If you were to turn a case with a neck diameter that is say .0005 under your chamber neck diameter you will get a very accurate measurement. A couple of thousandths off in length is not a big deal as long as your trim length is reasonable. Next time you need to do this try using a flat base bullet and seat it backwards leaving the neck longer than the base of the bullet. It makes the measurement easier and more accurate.