So I reloaded some ammo today and I was about to put the fresh ammo in a case when I spotted this:
No idea what happened there but I'm so glad I noticed it before I put it in the ammo case. Its REALLY hard to spot unless you turn it till the crack casts a shadow like in the pic. The case was fired only once so it cannot - or rather shouldn't be material fatigue.
Morale of the story: check the brass when you reload ammo! I was kinda sloppy, should have noticed it long before loading it.
The funny thing is, I noticed it when checking it a third time, and I usually never check ammo for 3 times.