Well, it seems the .257 Roberts is another one of those cartridges that gets grossly underloaded by certain companies. (Remington if you couldn't guess). The same with the 7 and 8mm Mausers. Look at these two from Federal with 100 and 120 grain Partitions.

Federal .243 Winchester 100 Grain Nosler Partition

Velocity

Muzzle 100 200 300 400 500

2960 2728 2508 2299 2099 1909

Energy in Foot Pounds

Muzzle 100 200 300 400 500

1945 1653 1397 1173 978 809


Federal 257 Roberts 120 Nosler Partition

Velocity

Muzzle 100 200 300 400 500

2780 2563 2356 2158 1970 1792

Energy in Foot Pounds

Muzzle 100 200 300 400 500

2059 1750 1478 1241 1034 856