I visited the LGS here in interior British Columbia. He says 6.5x55 is fairly common here, 7x57 less so but is around. He carried some ammo for it on his regular shelf.
He actually had three boxes of .257 Roberts on his "unicorn ammo" shelf in back. Said it's extremely unlikely any other shop would have any .257 ammo. He tries to keep some oddball calibers stashed. It was the old Rem 117 round nose. At another shop I visited the clerk wasn't familiar with .257 Roberts at all.
Larry: will 6.5x55 feed reliably in a 98 without changing the rails? It's shaped differently from the x57 mother case.