Lloyd3,
You can make cases from most of the different belted cases but the most convenient would be the mid length ( 06 length) ones. Those less than 30 caliber may be a few thousandths short after fire forming, but would be ok. If that bothers you, 300 Winchester can be trimmed to the precise length after forming. The most available would likely be either 300 Win. Mag. or 7mm Rem. Mag. The full length cases like 300 H&H can be used but would be more work.
Mike