Early in the 20th Century, several experimenters and wildcatters were playing with 25 caliber cartridges based on the 30-40 Krag case, similar to what Dr. Franklin Mann had introduced to the world in his treatise The Bullet’s Flight. One of those pioneers was N. H. (Ned) Roberts. He set out to design a rimless case having a capacity similar to the rimmed 25 Krag-Mann, considering the advances in powders since Mann’s experiments. Roberts settled on the 7x57mm Mauser case and began months of testing different bullets, barrels, and chambers. He finally settled on a 15 degree shoulder and a 2.160" case length, dubbing it the 25 Roberts. Michigan rifle maker A. O. Niedner agreed to make barrels, hand formed cases, and complete rifles, and shooters of the day commonly called the new cartridge the 25 Niedner Roberts.
In 1930, New York gun makers Griffin & Howe began to produce ammunition and rifles. They determined that case forming could be expedited if the case was left full length. Roberts tested the longer case, approved it’s design, and it quickly came to be called the 25 G & H Roberts.
In 1934 Remington proposed to legitimize the wildcat and introduce it in their Model 30-S Express rifle. They concluded that the manufacture of new brass cases could be facilitated by simply necking the 7x57mm case to 25 caliber, with no other changes. The new cartridge was named the 25 Roberts and cases were headstamped accordingly. Several noted riflemen raised flags of concern since it could be mistaken for the original 25 Roberts. Within a year the cartridge was renamed the 257 Remington Roberts and the headstamp changed to 257 REM. A year later, Winchester came on board with their cartridge named the 257 Winchester Roberts, headstamped 257 Roberts. With the passing of time both the Remington and Winchester cartridges came to be known as simply the 257 Roberts.