Here is picture of a 12ga size drawn brass case that was
made back in the 80s. Case is for the CAWS weapon system.
Case is belted, and it and the gun operated at 25,000 psi.
Its bore size is between 12 and 10 ga size, but the od of
the drawn case would let it start in 12ga chambers, so
they added belt so it couldn't go all the way in
to regular shotguns. Notice the thick sides and corner
near the base.Heavy enough for 25,000 psi. They loaded
it with big buckshot and tested other projectiles also.
They had a plastic card over shot and filler and rolled
over brass mouth for crimp. Ed

[Linked Image]

Ed Hubel