In this case, the .257 Roberts cartridges were loaded with Berger 115-grain HPBT Hunting VLD bullets. Though this was my first experience with .25-caliber Bergers, ...

The 257 Roberts is basically a 7x57 Mauser case necked down to take a .257 diameter bullet. The Roberts was designed in the 1920s, and Remington commercialized it in 1934.