Years ago when I started building the 338 edge, I bought 100 pcs of once fired 300 rum brass. I worked up a very mild load to break in the barrel and get all the brass matched to my chamber. 60 rounds were placed in styrofoam blocks that come with factory ammo. The other 40 were stored in plastic shell holders for factory ammo. This was 10 years ago. I finished the build a few weeks ago and finally got around to shooting it this weekend. The first 60 rounds came from the styrofoam. All had some tarnish on them so I wiped them down real good. I had no issues with these. I then get the last 40 stored in plastic. The first one I started to wipe and the bullet pushed right into the case. The neck cracked all the way down the shoulder. I usually inspect all of my reloads but this was 10 years ago so i cant remember if I did. Pick up the second round and same thing, cracked. I started looking closer and could see cracks in several cases. Not all were cracked all the way up the neck. Some had a small crack at the neck/shoulder junction so the bullet still felt firmly seated. On these I was able to push the bullet to the side and split the case wide open. Out of the 40 rounds, I found 25 had cracked. On the remaining 15 I pushed on the cases with no visible cracks. I did this under a magnifying lamp. I tumbled the first 60 rounds I shot and inspected them very closely. Not a single crack.

These were all stored on the same shelf side by side. All loaded at the same time. The only difference is the styofoam vs plastic. Has anyone heard of anything like this?

Here are some of the cracked cases



Sample of fired cases