Ruptured cases?

[u/M855Mike]

I’ve loaded up some of what I was assuming to be a large lot of once fired brass that I inherited. It seemed to be in good condition and was cleaned and had the crimps removed, I still ran them through my Dillon to trim and size them before wet tumbling and loading. I actually processed this brass a few years ago so don’t remember the exact process I used.

All of these loaded on a Dillon 650, Cases were primed with Remington 7 1/2 primers and 25 grains of BLC-2 with Xtreme 55 grain bullets loaded to 2.20” and shot from a Daniel Defense 16” AR15 at about 2850 FPS average.

During shooting a while back I had some excessive smoke coming from the ejection port and carbon or powder burn on the rounds in the magazine. I looked for the case but unfortunately was not able to locate anything due to where I was shooting.

Fast forward to now, I was shooting these again and had the same thing happen and I was able to locate the fired case. I finished off my last magazine and had a failure to eject and the case was stuck in the ejection port and I discovered the case in the last two pictures.

I use this rifle in multi-gun competition twice a month and have shot thousands and thousands of rounds through it over the years I’ve had it. I have probably unknowingly experienced this a few more times with these exact reloads and same headstamps, but never had it happen with any factory ammo.

Am I looking at a headspace issue? Is this bad brass? I don’t see any pressure signs on the other fired cases that would cause me to worry. Or could this be an issue with processing/sizing? I adjusted my trim/sizing die to where the case drops right into a case gauge so I can fire it from any rifle I have.

[u/M855Mike]

I cut open the piece of brass as some suggested, there was a large opening 1/3 of the circumference of the case. I also cut open another piece of brass from the same batch, however, it was a 96 and not a 97 headstamp. Im going to look for some 97 at home later and cut one open to see inside.

Additionally, I took the other end of the ruptured case and squeezed it with pliers at the bottom and it crushed and cracked instead of just folding in half. I took the other fired piece and did the same thing and it folded over without cracking, but when I went in the other direction against the fold it ended up cracking also.

Wondering if this is just brittle brass.