When Roy Weatherby founded his company in 1945, he revolutionized the firearms industry with a singular, radical philosophy: speed kills. At a time when the industry favored heavy, slow-moving bullets, Weatherby pioneered ultra-high-velocity, lightweight projectiles designed to deliver massive hydrostatic shock for immediate, humane kills on big game.
Most traditional Weatherby cartridges are instantly recognizable by their distinct design features: a belted brass case derived from the .300 H&H Magnum parent case, a signature double-radius shoulder, and significant freebore (unrifled space before the bullet engages the barrel) to prevent catastrophic over-pressure.
In recent years, Weatherby has expanded its lineup to include modern, unbelted options. Below is a breakdown of the entire Weatherby cartridge lineup, organized by caliber class.
1. Small Bore & Varmint (.22 to .24 Caliber)
.224 Weatherby Magnum
- Introduced: 1963
- Purpose: Varmint control and small-game hunting.
- Performance: Originally built for the scaled-down “Varmintmaster” Mark V rifle. It sends a 55-grain bullet downrange at over 3,600 feet per second (fps). It was the first Weatherby cartridge to break tradition by featuring an angled shoulder instead of a curved one.
.240 Weatherby Magnum
- Introduced: 1968
- Purpose: Varminting, pronghorn, and white-tailed deer.
- Performance: The .240 Wby Mag is the fastest commercial 6mm cartridge on the market. It utilizes a unique belted case identical in rim diameter to a standard .30-06, pushing a 100-grain bullet at roughly 3,400 fps with negligible recoil.
2. Quarter-Bore & 6.5mm Precision (.257 to 6.5mm)
.257 Weatherby Magnum
- Introduced: 1944
- Purpose: Open-country deer, pronghorn, and sheep.
- Performance: Famously known as Roy Weatherby’s favorite cartridge, the .257 is a legendary laser-beam. Launching a 100-grain bullet at a blistering 3,600 fps, its trajectory is incredibly flat, making point-blank holds out to 300 yards completely viable.
6.5 WBY RPM (Rebated Precision Magnum)
- Introduced: 2019
- Purpose: Mountain hunting, long-range precision, and medium game.
- Performance: A major engineering departure for Weatherby. The RPM family features a non-belted, standard-rim (.473″) case with a sharp shoulder design built to fit standard-weight actions. It easily drives 140-grain high-BC (Ballistic Coefficient) bullets at 3,000+ fps.
6.5-300 Weatherby Magnum
- Introduced: 2016
- Purpose: Extreme long-range deer and elk hunting.
- Performance: Created by necking down the massive .300 Weatherby case to 6.5mm, this stands as the fastest production 6.5mm cartridge on earth. It launches a 130-grain bullet at 3,475 fps, carrying devastating kinetic energy out past 500 yards.
3. Medium Big Game (.270 to 7mm)
.270 Weatherby Magnum
- Introduced: 1943
- Purpose: All-around North American big game up to elk.
- Performance: The first commercial cartridge released by Roy Weatherby. It completely outpaces the standard .270 Winchester, driving a 130-grain bullet at 3,375 fps and stretching the ethical maximum range on game by an extra 100 to 150 yards.
7mm Weatherby Magnum
- Introduced: 1944
- Purpose: Large open-country game (elk, mule deer, African plains game).
- Performance: Released nearly two decades before the famous 7mm Remington Magnum, it offers roughly 100 fps more velocity than its green competitor. It is flat-shooting, inherently accurate, and handles bullets up to 175 grains with ease.
4. The Powerful .30 Calibers (.308)
.300 Weatherby Magnum
- Introduced: 1944
- Purpose: Worldwide big game, elk, moose, and large brown bears.
- Performance: The undisputed king of the Weatherby catalog and the company’s best-selling cartridge of all time. Built by blowing out a .300 H&H case, it drives a 180-grain bullet at 3,250 fps with over 4,200 ft-lbs of muzzle energy. It provides hard-hitting, multi-species versatility across mountains and plains.
.30-378 Weatherby Magnum
- Introduced: 1996 (Developed in 1959 for military trials)
- Purpose: Extreme long-range hunting and precision benchrest.
- Performance: Born by necking down the massive .378 case to .30 caliber, this cartridge held world records for 1,000-yard accuracy for over 30 years. It fires a 180-grain projectile at an astonishing 3,420 fps. It is incredibly potent, though notorious for severe muzzle blast and fast throat erosion.
5. Medium-Bore & Dangerous Game (.338 to .460)
.338 WBY RPM & .340 Weatherby Magnum
- .338 RPM (2022): The lightweight, unbelted version built for standard actions, sending a 225-grain bullet at 2,800 fps.
- .340 Weatherby (1962): Weatherby’s response to the .338 Winchester Magnum. Utilizing the full-length .300 Weatherby case, it drives a 225-grain bullet at 3,000 fps. It is considered by many guides to be one of the finest elk and large-bear cartridges ever produced.
The Big-Bore Titans (.375, .378, .416, .460)
For dangerous game or stopping charging thick-skinned animals, Weatherby developed its large-bore family based on the massive, unique .378 belted case:
- .375 Weatherby Magnum: An improved version of the .375 H&H, offering roughly 250 fps more speed.
- .378 Weatherby Magnum: Developed in 1953 to replace the .375, it drives a 300-grain bullet over 2,900 fps.
- .416 Weatherby Magnum: Released in 1989, it steps up frontal surface area, sending 400-grain solid bullets downrange at 2,700 fps for massive penetration.
- .460 Weatherby Magnum: Released in 1958, it was designed for the explicit purpose of being the world’s most powerful shoulder-fired rifle cartridge. It fires a massive 500-grain bullet at 2,600 fps, generating nearly 7,500 ft-lbs of muzzle energy to drop stopping-class dangerous game instantly.
Technical Ballistics Comparison
The following table highlights the factory performance metrics across the distinct classes of the standard Weatherby family:
| Caliber | Bullet Weight (Grains) | Muzzle Velocity (FPS) | Muzzle Energy (Ft-Lbs) | Primary Hunting Application |
| .240 Wby Mag | 100 | 3,400 | 2,560 | Varmints, Pronghorn, Whitetail |
| .257 Wby Mag | 110 | 3,460 | 2,925 | Pronghorn, Open-Country Deer |
| 6.5-300 Wby | 130 | 3,475 | 3,485 | Mule Deer, Long-Range Elk |
| .270 Wby Mag | 130 | 3,375 | 3,290 | Whitetail, Mule Deer, Elk |
| 7mm Wby Mag | 154 | 3,260 | 3,635 | Western Big Game, Plains Game |
| .300 Wby Mag | 180 | 3,250 | 4,220 | All North American Big Game, Elk |
| .30-378 Wby | 180 | 3,420 | 4,675 | Extreme Long-Range Big Game |
| .340 Wby Mag | 225 | 3,000 | 4,495 | Elk, Moose, Large Bears |
| .460 Wby Mag | 500 | 2,600 | 7,500 | Dangerous Game (Elephant, Cape Buffalo) |
The Verdict: Whether you choose the laser-like trajectory of the classic .257 or the raw, thumping power of the benchmark .300, Weatherby’s cartridge lineup continues to dominate the high-velocity hunting market by squeezing out every possible foot-per-second of performance.