Unless it's changed, you could only buy RN ammo for .257, so if you want full potential, you need to handload with spitzer bullets of good construction, like the Nosler Partition. I think a .257 so loaded will kill elk in a suitable situation. For smaller game, it's excellent.

What killed off the .257 was low powered RN factory ammo and the appearance of the 6 mms, hyped a lot by Warren Page at, Field & Stream.

Jack O'Connor liked the .257, but he handloaded for the caliber.

I wouldn't buy a .257 as my primary hunting rifle, but as a luxury item for the right circumstances, it's fine.