223 Case Separation

[wichaka]

Anyone come across such a thing. I've seen headspace issues, but not so clean cut.

52375

[P2000]

Do you have any more information about this picture? The rounds appear to be unfired, with massive bullet setback, and have a crease. None of that is case separation. Maybe they are messed up reloads? They even look too long to be 223, but it might be the picture.

On second glance, I see it now. There is a torn fired case on top of each unfired case. That's crazy. A round is fired, case separates, rear half of case removed from chamber, then upon attempting to chamber the next round it gets stuck to the front half of the fired torn case, and they are extracted as a whole.

Pics of the rest of the torn cases might have clues. My guess is that this is caused by a terrible chamber.

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[Coal Dragger]

Yeah there’s something really wrong with the chamber in that rifle. Might be headspace, or might have been a big ass nick in the chamber reamer that caused a prominent and sharp ring in the chamber.

What I want to know is who is so hell bent on firing a clearly broken gun that they would clear that type of malfunction repeatedly and continue to shoot it?

[bigedp51]

If you look at the brass hardness gradient chart in the lower left below you can see the separations occur just above the hardest part of the case.

Meaning the upper and softer part of the case is gripping the chamber walls when fired and the harder section is stretching to meet the bolt face.

Lake City 5.56 brass is harder than commercial .223 brass and you can see the case separations are higher up the case due to the hardness gradient.

My guess is the case shoulders are being bumped back too far allowing the case to stretch excessively to meet the bolt face.

Example I have a standard .223 Lee full length die that will push the shoulder back .009 if the die is set up per the instructions.

In addition a small base die will push the case shoulder back .003 more than a standard die, if the die contacts the shell holder.

https://i.imgur.com/JcVlKzc.jpg

Below a fired Lake City case in my Hornady cartridge case headspace gauge, and I set the die to bump the shoulder back .003 shorter than this measurement.

https://i.imgur.com/OJqNmQH.jpg

NOTE, info to readers, the cases pictured by the OP, the case separated and the rear of the case ejected and a new round started to chamber and became stuck in the forward part of the fired case that did not extract. This is a old trick with bolt actions to help remove the forward part of a case head separation by chambering a new round and jam it into the stuck section of the case.

[markm]

That is approximately the total number of .223 separations if had in my entire shooting life. Could be the gun.... could be the die setting.

You can tell when you're resizing a case that was fired in an excessively head spaced gun simply by the feel on the press. I'd get a few here and there when scooping up brass at the range. I toss them out.

[bigedp51]

The image below shows head clearance that is the "air space" between the rear of the case and the bolt face. And the head clearance is the equivalent of how far the case shoulder is pushed back during sizing.

https://i.imgur.com/HK76WCp.jpg

Example below of a .303 British Enfield rifle at maximum military headspace of .074 and a case with a rim thickness of .058. This gives you .016 head clearance and the case will fail with a case head separation after just 1 or 2 reloadings.

https://i.imgur.com/sHgqVJR.gif

Bottom line, excessive shoulder bump causes case head separations, and chambers and dies vary in size. And for longer case life your shoulder bump should be .002 to .003 shorter than chamber headspace. Meaning setting the die up per the instructions and contacting the shell holder might be pushing the case shoulder back too far and creating too much head clearance.

And as I stated before I have a Lee .223 die that can push the case shoulder back .009. And a cartridge will not last very long if it stretches .009 every time the case is fired.