A couple years back I bought a new unopened bag of Remington 3006 brass at a gunshow. I opened the bag last week and loaded them up to fire form the brass. A light load. Shot all 50 no problems. I threw them in the Tumbler for an hour. I then inspecting the brass and one case just did not look right in the neck area. I keep a magnifying glass at the loading bench.
Looking at this one piece of brass, there are very small cracks and pin holes in one side of the neck area. I crushed this one but intend to keep an eye on the remainder of this lot. I am thinking this was just a defect in the one case.