cracked butt
Member
Sounds like you mean to say "HSM."
This ammo has known issues.
The case had stretched to the breaking point already in a machine-gun or something, and was just waiting to crack when you fired it again.
HSM was my second choice, Ultramax was my first guess as to the manufacturer of the ammo. Both remanufacture ammo from LC brass which more than likely comes from machinegun ranges. Black Hills does too with their remanufacured ammo, but I'm not sure if they buy better brass to start with as this doesn't seem to be a probablem often attributed to them.