Have lots of once-fired 284 Winchester brass, trying to form them to 6-284.

I've tried greasing them up and running them into my 6-284 seating die, then the 6-284 FL sizing die. Also tried just one pass into the 6-284 FL sizing die. Crushed necks.

Do I need to anneal? Or just find a die to form them to an intermediate size? Is two steps enough? Can anyone recommend a cheap die to do this?

Thanks,
jkpq45