Incipient Case Shoulder Separation Viewed from Inside?

vtmarmot

vtmarmot

P Magoon, Livin' Free NH
A couple of years ago I had a 6 PPC case separate right at the shoulder. I had a great match going but the shoulder wouldn't come out until I got back to the cleaning table. At the time, forum members suggested it was due to excessive shoulder pushback. I can buy that. I probably should trash the rest of the cases, but they shoot good. I got the idea of using my Hawkeye borescope to detect any future problems. My issue is - I don't know what I'm looking for.

I know what incipient separation in the case body looks like, and I don't have any. The bend at the shoulder is another matter. The case that separated has a lot of blue-green corrosion throughout the case, and especially in the shoulder. Some of the other cases have some of this corrosion right in the bend. I wonder if that is a predictor of problems or if I should look for something else?
 
Are you talking about at the top of the shoulder, at the base of the neck, or at the bottom of the shoulder?
 
At the base of the shoulder. The fat part.

After the separation, a piece the shape of a funnel was left in the chamber. It came right out with a brush, however.

Interestingly, this was a score match, and the shot was a 10.
 
May not have any relevance, but a good few years back, I dissected a Norma .308 case that I'd passed quite a few bullets thru shooting target rifle. At the body/shoulder junction there was a tiny "roll" or bulge of brass that looked like those cosmetic strips that they used to put between panels on cars half a century ago. It was possibly formed during case resizing.
 
If brass has become brittle from work hardening*, there is no warning sign. It just cracks.
Has brass been annealed?

Some chemicals can make brass brittle, annealing will not correct it.
Avoid ammonia, ammonia vapors, vinegar, ethanol product around cartridge brass. This is not a short term problem. Mostly happens to ammo stored for a few years.

How old is the powder. If going bad, it may attack the brass.

Then there is just bad brass, like this .
FCBrass1997.jpg
 
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It doesn't matter why the case separated or where it separated. Trash those cases and make new ones! You likely turned the cases into the shoulder but again, it doesn't matter...make new cases.
 
Hornady Reloading Manual

I have some sectioned cases I will take pictures of and post them when I get a chance.

You can also check the older Hornady reloading manuals (1980-1990's vintage). In the instructions for how to reload for rimless cartridges, they give a nice illustration and explanation on the stretching of the brass at the web from excessive resizing.

Greg Walley
Kelbly's Inc.
 
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