This requires great care, but, you can take an appropriately sized thread-tap, manipulate it with your finger-tips & needle-nosed pliers, so it gets a bite into the brass, then knock it out with a cleaning rod.

I did this a couple of times with a .303 SMLE that had complete head separations with reloads.

(To protect the exposed part of the chamber, you could wrap some of the tap with masking tape).

I have never seen a case separate at the shoulder. It would be interesting to see pictures of that when it is removed.