One of the finest deer/varmint/hunting cartridges made. Grab it.
The .257 Roberts was based on the 7x57 Mauser case, and the .244/6mm Remington was an offshoot of that. As far as components go, the .257 bullets are common, and brass can be obtained as it is still produced. You can also make your own cases out of 6mm Remington, 7x57 Mauser or even 8x57 Mauser if needed.
The .257 Roberts is a bit more versatile than the .243/6mm calibre as it has the ability to take a bit heavier bullets in the 117-120 range for the larger game animals.
It also makes a very accurate, light recoiling rifle. WARNING : If you have a wife or girlfriend, I would not let them fire it. If you do, you might find that they will appropriate it, and you will then NOT have a .257 Roberts, but they will though.
.