split case mouths

[HRider]

Three friends and I went to the range yesterday to run some rifle and pistol drills. We had six different rifles between us. At the end of the day we picked up all of the brass. No one wanted the rifle brass so I brought it home with me. As I was separating out the pistol brass, I started noticing a few pieces of rifle brass with split case mouths. I checked the headstamps and they were mixed between WCC and LC (don't recall the year of each though). I didn't see any sign of overpressure, primer strikes looked normal. I knew that they didn't come out of either of the rifles I was using as I was firing PPU ball and Wolf. I sent a message to the other guys to see if we could figure out which rifle the split cases came out of. So far, no one believes it came from their rifle (one was using PMC, no one had any Winchester, no reloads, etc). There was some brass on the ground when we started, so it is possible that it came from someone before us.

Now that I have rambled, my thinking behind what would cause rifle cases to split at the mouth is an out of spec chamber throat. Am I missing something?

Hurley

[fastluck13]

It is common. Brass that has been loaded a few times can fail there. Annealing can prolong life but that is too much work for me.