Rifle-cartridge innovation has historically focused on velocity. Weatherby built its company and reputation on this premise. This began to change as the 6.5 Creedmoor rose to stardom. For the last decade, the emphasis has been on faster twists and higher ballistic-coefficient (BC) bullets. Hornady has exploited this very well with its Creedmoor, PRC and ARC cartridges. With its RPM (Rebated Precision Magnum) line of cartridges, Weatherby combined fast twists with what it does best—high velocity—and the company has created a new .257-caliber cartridge called the 25 Weatherby RPM.
Introduced in 1963, the .284 Win. was a failure by most any metric. Though it developed somewhat of a cult following, it’s now mostly forgotten. The .284 Win. was unique because it had a .500-inch diameter case at the base, but it had a rebated .473-inch rim. This allowed for more powder capacity in a short-action cartridge with a rim diameter the same as the .308 Win. Though now almost a relic, the .284 Win. fathered or inspired other cartridges, like the .450 Bushmaster, .30 Rem. AR and 6.5-284 Norma. It’s also the parent case for Weatherby’s 6.5 PRM and 338 RPM, and now the new 25 RPM.
Weatherby’s RPM cartridges utilize a lengthened version of the .284 Win. case that retains the rebated .473-inch rim, the .500-inch base and the steep 35-degree shoulder. This allows for an increased powder capacity over other standard (non-magnum) cartridges. For example, the .25-’06 Rem. case—which has a .473-inch rim diameter and a .469-inch base—holds 65 grains of water and the Weatherby 25 RPM case holds 72 grains.
The capacity to hold more powder is one thing, but the 25 RPM is also loaded to a maximum average pressure (MAP) of 65,000 psi. The .25-’06 Remington has a MAP of 63,000 psi, so this gives the 25 RPM a substantial velocity advantage. For example, a .25-’06 can push a 120-grain bullet to about 2,975 fps and the 25 RPM can exceed that velocity with a 133-grain bullet. Of course, Weatherby’s .257 Mag. is faster than both, easily spitting 120-grain bullets out of the barrel at 3,300 fps. So, you might be wondering why Weatherby is bothering with the 25 RPM, and, more importantly, why you should care.
Four factory offerings will be available at launch, from a 107-grain Hammer bullet to a 133-grain Berger projectile. photo: Richard Mann
Two reasons: First, because the 25 RPM works with a standard .473-inch bolt face, has a maximum case length of 3.34 inches and has a case body that’s slightly smaller than the .257 Weatherby Mag., it will work in the same size action as the .25-’06 Rem. This is particularly important to Weatherby, because the company can chamber the 25 RPM in its six-lug Mark V action. The .257 Weatherby Mag. requires the nine-lug Mark V action, and the six-lug action is slimmer and 28 percent lighter.
The second and more important reason deals with twist rate. The .25-’06 Rem. and the .257 Weatherby Mag. are saddled with a slow—by modern standards—twist rate of 1:10-inch. This limits their ability to stabilize the new crop of high BC, .257-caliber bullets inspired by the 25 Creedmoor. The 25 RPM has a twist rate of 1:7.5-inch and will outperform the .25-’06 and 25 Creedmoor at any distance. At 300 yards and beyond, the 25 RPM can hang with and even outperform the super fast .257 Weatherby Mag.
I have a 22-inch barreled Weatherby Mark V (six-lug) Backcountry Guide TI rifle chambered for the 25 RPM that I’ve been testing. With a 23.8-ounce Swarovski Z8i 2-16×50 mm riflescope in Talley lightweight rings, it weighs just slightly less than 7 pounds.
I’ve been shooting three of the four factory pre-production loads as well as some handloads, and I’ve been impressed. With three of the five loads tested, the combination will easily meet Weatherby’s sub-MOA three-shot guarantee. Initially, Weatherby will be offering four factory loads utilizing the 107-grain Hammer bullet, the 117-grain Hornady SST and Barnes LRX bullets, and the ultra-high BC, 133-grain Berger Elite Hunter bullet.
I’m very fond of .25-caliber cartridges, which is why I necked the 6.5 Creedmoor down to .25-caliber—creating the 25 Creedmoor—a decade ago. But, by combining the company’s affection for high velocity with the rebated rim of the .284 Win., a higher-capacity case and a faster twist rate, Weatherby has created what appears to be the best-performing .257-caliber cartridge yet devised. You’d be hard pressed to find another cartridge that shoots as flat, from a featherweight rifle, with less recoil. And, aren’t lighter rifles, flatter trajectories and less recoil what hunters and shooters have been after all along?
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