Estimated reading time: 4 minutes
Weatherby introduced the 25 WBY RPM, a modern, fast-twist 25-caliber cartridge built to drive heavy, high-ballistic-coefficient bullets at magnum-level speeds from standard long actions.
New Cartridge Aims for Modern Ballistics
Weatherby’s newest addition to its Rebated Precision Magnum (RPM) family packs a .257-inch bullet into a rebated-rim design with a fast 1:7.5 twist rate. This loading is called the 25 RPM. The company reworked its RPM case to fit long, sleek projectiles without losing usable powder space, making it easier to load heavy bullets with high ballistic coefficients.
The RPM name stands for Rebated Precision Magnum, and this cartridge follows the same compact-case philosophy that Weatherby used in its popular 6.5 and .338 RPM rounds. The goal is simple: magnum performance in a streamlined package that fits modern rifle actions.
Key Cartridge Specifications
- Bullet Diameter: .257 inches (6.35 mm) — quarter bore class.
- Parent Case: Derived from 6.5 WBY RPM brass.
- Maximum Overall Length (OAL): 3.34 inches — matches long-action standards.
- Case Length: 2.40 inches — slightly shortened for usable seating room.
- Neck Length: 0.262 inches — holds heavy bullets securely.
- Shoulder Angle: 35 degrees — modern shape for consistent performance.
- Rebated Rim Diameter: .473 inches — fits standard bolt faces.
- Seating Room: 0.940 inches of bullet seating space.
- Twist Rate: 1:7.5 — stabilizes heavy for caliber bullets.
Ballistics and Performance
Early factory loadings show the 25 RPM can push bullets in excess of 3,000 feet per second. Lighter projectiles around 107–117 grains reach up to roughly 3,350 fps, while heavier 133-grain bullets hover near 3,000 fps from a 24-inch barrel.
This performance puts the 25 RPM in a different league than older quarter-bore cartridges that use slower twist rates and shorter overall lengths.
Those older designs often struggle to stabilize long, high-BC bullets that today’s hunters and shooters prefer, since they were produced in an era that utilized slower twist-rate barrels.
What Shooters Should Know
Weatherby designed the 25 RPM to fit both its Mark V six-lug actions and the newer Model 307 long action. That means new rifles chambered for this cartridge will have options for hunters and range shooters alike.
The RPM’s modern case geometry aims to give shooters flatter trajectories, stronger downrange energy, and more consistent performance with a wide range of bullet weights — all while keeping rifles lighter and easier to carry than traditional magnum setups.
The Bottom Line
The Weatherby 25 RPM brings a fresh take to .25-caliber hunting and precision shooting. It pairs modern cartridge design with magnum-level ballistics and supports today’s trend toward heavier, high-BC bullets.
Learn more about the new Weatherby 25 RPM cartridge here.
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Riley Baxter is a seasoned hunter, outdoorsman, and competitive shooter with deep roots in the backcountry. He has guided professionally for bears, bighorn sheep, and other big game across rugged terrain, bringing firsthand knowledge of what gear actually works in the field. When he’s not chasing game or running drills on the range, Riley is likely in the garage customizing his rifles, pistols, or backcountry kit.
A competitive pistol shooter and lifelong firearms enthusiast, Riley brings both precision and creativity to every piece of equipment he touches. Outside of the gun world, he works as a perfusionist in Montana, a vital role in heart surgery that demands attention to detail, critical thinking, and mental fortitude.
Experience:
– Professional Hunting Guide – Guided for bears, bighorn sheep, and more in some of the West’s toughest country.
– Competitive Shooter – Skilled USPSA pistol shooter with a passion for precision and performance under pressure.
– Custom Builder – Enjoys building and tuning firearms and equipment to meet the exact demands of the hunt or the range.
– Experienced Marksman – Experienced in long-range hunting and precision rifles to meet the demands of the terrain of the West.
– Montana-Based Perfusionist – Medical professional accustomed to making critical decisions in high-stakes environments.