Roy Weatherby's flagship .375 and the parent case of the .460 Weatherby Magnum. Generates dramatically more energy than .375 H&H with 300-grain bullets at over 2,900 fps — making it one of the most powerful commercially available cartridges for the largest African game.
Type: Rifle
Introduced: 1953, United States
Parent case: .416 Rigby
Standardization: SAAMI
Bullet diameter: 0.375" (9.53 mm)
Case length: 2.913" (74 mm)
Overall length: 3.656" (92.86 mm)
Max pressure: 62,000 PSI
Rim type: Belted
Primer: Large Rifle Magnum
Typical twist rate: 1:12
Muzzle velocity: 2900–3180 fps
Muzzle energy: 5040–6740 ft-lbs
Effective range: 400 yd
Common bullet weights: 270, 300 gr
Primary use: Hunting
Production status: Active
Also known as: .378 Wby Mag
History: Roy Weatherby introduced the .378 Wby Mag in 1953 on his proprietary large belted case. Weatherby's philosophy was maximum velocity at all calibers — the .378 pushes 300-grain bullets 300+ fps faster than .375 H&H, generating roughly 50% more muzzle energy. The .378 case became the parent for the .460 Weatherby Magnum, giving it outsized importance in Weatherby's cartridge lineage. Professional…
Notable firearms: Weatherby Mark V
Similar cartridges: .375 H&H Magnum, .460 Weatherby Magnum, .375 Ruger