Concertinaed 20mm x 128

The attached pictures show a concertinaed 20 x 128mm case, H/s BM 278 83. I am guessing that this is the result of a misfeed, but as I am often wrong, has anyone else seen anything like this. Thanks in advance for comments.


These should be from stress tests for the cases. Some countries did/do this as part of the QA.

I’ve seen these sort of cases before in an ammo plant. I was told it was a stress test for the paint/laquer.

This was also done to brass cases. I seriously doubt the paint story.