Roy Weatherby's flagship cartridge and the one that made his name. Operates at higher pressure than most magnums, producing velocity figures that seemed impossible in 1944.
Type: Rifle
Introduced: 1944, United States
Parent case: .300 H&H Magnum
Standardization: SAAMI
Bullet diameter: 0.308" (7.82 mm)
Case length: 2.825" (71.76 mm)
Overall length: 3.56" (90.42 mm)
Max pressure: 65,000 PSI
Rim type: Belted
Primer: Large Rifle Magnum
Typical twist rate: 1:10
Muzzle velocity: 3000–3500 fps
Muzzle energy: 2997–4350 ft-lbs
Effective range: 700 yd
Common bullet weights: 150, 165, 180, 200, 220 gr
Primary use: Hunting, Long Range, Big Game
Production status: Active
Also known as: .300 Wby Mag
History: Roy Weatherby developed the cartridge in 1944, a year before formally founding Weatherby Inc. in 1945. The .300 Wby Mag was his calling card. Its double-radius shoulder design reduces case stretching. For decades it was the most powerful commercial .30 caliber cartridge available. Celebrities like John Wayne, Roy Rogers, and Herb Klein hunted with Weatherby rifles.
Notable firearms: Weatherby Mark V, Weatherby Vanguard
Similar cartridges: .300 Winchester Magnum, .300 H&H Magnum, .300 Norma Magnum