Internal Ring Questions

[poline]

From previous reading on this forum I got impression that with a flated and bent, hook on the end, paper clip one could feel the internal ring inside a brass shell down at the base or head. I have several suspect brass, but I'm unable to detect the internal ring with the paper clip. What, I wonder am I doing wrong?
Can anyone one provide a picture of what the internal ring looks like on the outside of the brass? Thanks

[SL1]

The appearance of the brass on the outside is NOT a good indicator of a thinning ring on the inside. SOMETIMES, there is a bright ring on the outside where there is thinning on the inside. BUT, sometimes there is NO indication on the outside, or it is made inconspicuous by tumbling and polishing. On the other hand, sometimes there IS a bright ring in about the same place, but it is actually casued by burnishing the normal "pressure ring" of an expanded case with the sizer die. The best outside indication of a thinning ring is a bright ring that appears WHEN THE CASE IS FIRED, so you know that it is caused by firing that round. I don't really know if autoloader extraction can still make a bright ring on the pressure ring, so I can assure you that even that is a sure indication of a thinning ring, inside.

That is why the paper-clip test is recommended. It takes a little mental calibration to know what you are feeling with the tip, so that you aren't throwing away cases that are good or missing cases that then fail.

The best way to get that calibration is to section some cases that you have first tested with the clip tip. I used to section every case that I was going to throw away because of what I thought I felt with the clip. Some of the early ones were actually still good. Once I was confident about what the "feel" indicated, I quit sectioning cases. I haven't separated a case head, yet.

Sectioning a case is easiest with a Dremel tool. But, youu can do it by drilling a hole in a block of wood thatholds the case, putting the block in a benchise to hold it steady, and cutting the case axially from the head end. The, clean-up the cut with a file and you can actually measure the case wall thinkness in any apparent thinning ring as well as nearby, and learn what a certain depth of ring feels like with the clip tip.

If yopu are going to throw away some suspect cases, this effort may allow you to save them (except for the ones you actually cut).

SL1

[454PB]

Plus 1 for what SL1 has said.

Another method for determining when a head separation is looming is case stretching. Brass has to go somewhere as the head begins to thin....and that's forwards. Assuming you measure and/or trim to recommended length each time the case is resized, after about 4 trimmings, you're getting close to separation.

The paper clip trick has been inaccurate at best for me.

I've found with proper die settings for sizing, my magnum rifle brass lasts up to 15 firings before it's been trimmed 4 times, and by then the cases are either splitting at the mouth, or relegated to cast bullet (low pressure) loads.

The mouth splitting can be retarded by annealing the brass, but I figure by 15 loadings, I've gotten my money's worth.

[Ike666]

Like you I first read of the technique here in this forum and began trying it. And, like you, I wasn't sure what I was doing or what I should be feeling. I'd drag the tip vertically up the inside of the case wall and wonder what I should feel.

Then I had a case rupture at the web. At last a known positive incidence. I started by running the paperclip up right at the rupture point and could feel a very definite trough as it came off of the web onto the case wall. Then, because it was not a complete separation, I moved around the circumference testing at several places. I could feel the trough for better than 75% of the circumference. There was a relatively small area where there was no perceptible trough. Next I uses the Dremel and cut open the case lengthwise to see what the interior actually looked like. I could clearly see the expansion just above the web 3/4s of the way around and an area with no observable change.

Having completed that I felt comfortable about what I was feeling and started inspecting cases on a regular basis.

I also found a neat set of dental picks that I just ordered to use for this operation:
http://www.duluthtrading.com/store/d...cessor=content

[amamnn]

As Ike mentioned, proper case inspection is a must--it also helps to pass the time on rainy days, which we have here a lot.................but tommorrow we are sheduled to see that big light in the sky so I have my kit all ready to go to the range.................


Unless you have a bad case-- you should have some warning about head separation, usually hard bolt lift or hard extraction after the bolt lift. The use of quality brass will help to avoid this problem. I've blown Lapua 30BR cases out to the point where I had to use a screwdriver to open the action and there was never a trace of head separation. The cases were subsequently FL sized and used for many times afterward.

[poline]

Fellows thank you for the replys and advice. THANK YOU, VERY MUCH.