Roy Weatherby developed the 257 Weatherby Magnum by blowing out, shortening and necking
down the 300 H&H Case.
He introduced the cartridge, with the distinctive double-radius shoulder in 1944.
The .257, .270. and 7mm. Weatherby Magnums are similar in size and capacity, and are all based
on the .300 H&H case shortened to 2.545".
Today, more than 65 years after its introduction, the .257 Weatherby Magnum remains king of
the factory .25 caliber, with 75 grain projectiles traveling up to 3,800 Feet per Second.