Hi guys,
I couldn't get a picture of this on the phone that was up to scratch so hopefully I can describe this well enough to get an answer.
For s**ts and giggles I cut open a .308 case just to have a look. The brass is 3 or 4 times fired.
I sawed the head off so I had just the tube. Looking down the tube, it's obvious one side of the case is thinner for it's whole length than the other. Looking at the base of the cut sort of looks a bit like a crescent if you know what I mean.
I know brass isn't made like this but if you imagine if you had a rod of brass and drilled a whole down the middle, but drilled the whole slightly off centre. Looks like that.
After that I cut the length of the case and folded it out like a little sheet. There was no separation beginning, just the thinner wall along one side.
Is that thinning from firing or a manufacturing discrepancy?