My experience of re-sizing industrial 8G hulls has shown that the process is easier and less likely to damage/malform the brass head if the squeeze is carried out in two or even three steps using steel dies of different internal diameter, reducing from wider to narrower at each stage. Use of an Arbor press of good size also helps reduce the grunt factor.
You may be able to get good advice for your problem on the CastBoolits website, notably relating to induced changes in the brass integrity and associated weakening which may arise from resizing procedure.

Last edited by greener4me; 05/17/21 05:30 AM. Reason: typing error.