This question was asked in a previous post but was not answered. Was wondering if anyone has tried to size .458 inch bullets to .452. I want to try some 300-350 gr. bullets in a muzzleloader with sabots. Possibly also use them in 454 Casull.

You can probably do this successfully with cast bullets. If you attempt to do so I would use one of the Lee bullet sizers in which which you force the bullet through nose first in your regular reloading press, which has plenty of leverage.

I don't recommend trying this with jacketed bullets, because in sizing a jacketed bullet down the jacket has more memory than the lead core and will spring-back more, making the core loose in the jacket, and it probably won't shoot very well.
Doing so also takes considerably more effort than sizing a cast bullet a few thousandths of an inch.