Just rebarreled a .300 RUM 700 Rem. to .416 ruger - used a Shilen #4 SS & did the whole job on my lathe. Cut the barrel to 22" and crowned - will give it a light bead blasting to match with the Remington action. Got a Manson reamer from 4D reamer rentals and she cut a smooth chamber, I think that the reamer was brand new.
Now have find some .416 Ruger dies - Hornady said that they will have them in March.