I' ve never done this so this is my best guess...... PLEASE make sure I' m on the right tack before you do any of it. I' ve heard 7mm -08 is a .308 necked down to 7mm so start with .308 form them and then neck ream them to thickness. They make a reaming tool that fits your case trimmer it goes in , in place of the pilot.

.243 win seem to thcken when resized so I ream them to ensure thickness.

Good Luck