.458 Lott dies are cheap if you call RCBS/Huntington direct on their 800 number (sorry, no gots) Running a longer Lott into a shorter Magnum sizing die can result in wrinkled cases or only partial resizing.

BTW: Check with midwayusa.com for prices on 458 Lott ammo and brass. They seem to be quite reasonable, even with the price increase.