What causes this?

[Santa Cruz Armory]

I reloaded a bunch of 7.62x39 a while back (this pic is of .223) and about 1/3 of it did this...I was well under the maximum load.

[JeffM]

I'm no expert, but it looks like it could be brittle brass. An improper or non-existant annealing of the neck maybe?

What's the headstamp?

[anyracoon]

Is it once fired or range scroundge? Also reloading die adjusted wrong could result in no chamber support on shoulder/neck area.

[Santa Cruz Armory]

I'm no expert, but it looks like it could be brittle brass. An improper or non-existant annealing of the neck maybe?

What's the headstamp?

Is it once fired or range scroundge? Also reloading die adjusted wrong could result in no chamber support on shoulder/neck area.

It's Winchester brass. This is a reload of my once fired brass.

[1lostinspace]

Did you get primers popping out?
Did you crimp the hell out of it?
Have you tried it with different brass same load?

[Santa Cruz Armory]

Nope, no bulging primers and no crimp... it was a mix of once fired I had