Reloading the 6.5 Weatherby RPM Cartridge: How To

The precision performance rifle situation has changed significantly during the last decade or so. For more than a century, the venerable .30 caliber has been the most popular hunting caliber. And for much of that period, it also served as the most prevalent caliber used in competitive rifle matches. The 6.5mm (.26 caliber), on the other hand, has been maligned, ignored, scoffed at, denigrated…or any other clearly derisive term you might choose. That characterization was exactly the opposite in Europe. The 6.5mm caliber was—and is—quite popular, so at least a few commercial and military-surplus rifles were imported here. Their owners either shot military ball ammo, bought expensive foreign-made hunting ammunition, or converted the rifles into custom guns chambered for more popular U.S. cartridges. Until recently, only three 6.5mm rounds were introduced domestically since the 1950s: the 264 Winchester Magnum, the 6.5 Remington Magnum, and the 260 Remington. There were also wildcats, like the 6.5 JDJ, 6.5-284 Winchester, and 6.5-06, that garnered some attention. A couple eventually gained S.A.A.M.I. recognition, but the 6.5 Rem. Mag. and the 6.5-06 are no longer listed in S.A.A.M.I. specifications. Now ask yourself and your hunting buddies this question: “Do you own or have you ever considered buying a rifle chambered for any of these rounds?”

Obviously, most of you would answer, “No.” Otherwise, sales of these excellent hunting rounds would have fared better. The two belted magnums are nearly obsolete, and the once-popular 260 Rem. has been all but overwhelmed by the now wildly popular 6.5 Creedmoor—both as a target round and a hunting round. For whatever reason, after Y2K, interest in .26-caliber cartridges completely reversed, going from being minimal to almost unbelievable. The proprietary 6.5 Grendel was first, but it sputtered until S.A.A.M.I. made it legitimate. The 6.5 Creedmoor is aptly noted as “the slowest occurring overnight sensation” on record. Introduced a decade ago and envisioned as strictly for competitive shooters, hunters finally noticed it, and the Creedmoor has become the most popular chambering in all types of rifles. Two more recently introduced cartridges, the 6.5-300 Weatherby Magnum and the 26 Nosler, are “screamers” intended for the extreme-range hunting crowd. And the 6.5 PRC (introduced by Hornady in 2018) might be characterized as the Creedmoor on steroids and is intended for the same purposes. In 2019 Adam Weatherby, company founder Roy Weatherby’s grandson, introduced the 6.5 Weatherby Rebated Precision Magnum (RPM) into the ranks of 6.5mm cartridges.

The Weatherby Heritage

Everybody loves a success story, and Roy Weatherby’s pursuit and achievement of his dream is one of the best known in the firearms and hunting industry. As a young man, he and his wife left the dust bowl of Kansas in the middle of the Great Depression and settled in Los Angeles. He became a salesman for an auto club and soon opened a small gunshop. On a hunting trip in Utah, Roy wounded a deer with his 30-06 and was unable to track it. He concluded that a faster round would have delivered greater shocking power, and he likely would have avoided losing the deer. This fervent belief in the efficacy of “shocking” energy led to his developing the series of Weatherby Magnum cartridges. From the mid-1940s until his death in 1988, Roy developed a total of nine most-powerful-for-caliber hunting cartridges: the 224, 240, 257, 270, 7mm, 300, 375, 378, and 460 Weatherby Magnums.

He also eventually developed the super-strong Weatherby Mark V rifle action. At first, Roy built custom rifles on surplus 1898 Mauser and Winchester Model 70 actions. He also used Belgian FN Mauser and Danish Schultz and Larsen actions. It wasn’t until 1958 that the original Mark V action was finally proven and put into production. The Mark V’s primary design feature is its interrupted thread, nine-lug bolt versus the typical opposing two-lug bolt design used on most bolt actions. For many years, various foreign and domestic manufacturers made the Mark V, but in 1994, all production was moved back to Weatherby’s facilities in California. Roy’s son and successor, Ed, added four more cartridges to the lineup: 30-378, 338-378, 416, and 6.5-300 Weatherby Magnums. Adam’s new creation (the 6.5 Weatherby RPM) omits the ubiquitous belted case and the distinctive neck profile and lays no claim to being the hottest .26-caliber rifle cartridge, but its performance is still all Weatherby. It and other popular hunting cartridges are offered in Weatherby’s scaled-down six-lug Mark V rifle. Recently, Weatherby, tired of California’s anti-gun politics and government officials, pulled up stakes, and moved to Sheridan, Wyoming. The 6.5 Weatherby RPM Accumark Mark V used in this review was built in the new facilities and is so marked.

Reloading the RPM

Weatherby provided some once-fired brass in addition to samples of the three factory loads, so I had ample cases to prep and reload. Hodgdon forwarded a comprehensive data sheet listing lab-tested recipes for several different bullets weighing from 120 to 150 grains. All of Hodgdon’s loads were developed in a 26-inch pressure barrel. The Accumark sports a 24-inch barrel, so I didn’t expect my velocity results to necessarily match those of Hodgdon. The steps and checks in prepping brass and assembling 6.5 Weatherby RPM test loads are no different than if you’re loading any other rimless, bottlenecked rifle cartridge like the 270 WSM or 30-06. First, I typically dry tumble the fired cases in treated corncob media. Once clean, they’re individually inspected for damage or defects. If I’ve loaded a batch more than two or three times, I usually decap them before resizing to “feel” the force required to punch out the primers. If I reject more than a couple for loose pockets from a small lot of cases, I will either dump the whole batch or pay close attention later when seating new primers to again gauge if too little force is required, indicating the pockets are too large. You shouldn’t depend on a “loose” primer to safely seal a cartridge case when pressures may be pushing 65,000 psi!

If everything appears okay, I continue with prepping the cases. There’s no belt, so you size it to headspace on the shoulder. The Mark V Accumark is intended for hunting, so to ensure no ammo problems in the field, I recommend that you full-length resize each one. I incrementally adjusted my Redding sizer die in the press and resized a few cases until one chambered with just a tad of resistance. My intent was to avoid setting the shoulder back too much, creating excessive headspace. Turned out all my careful adjustments weren’t necessary because Redding’s full-length sizer die is so precisely matched to the #1 shellholder. I could have achieved the same result by simply screwing the die into the press until it touched the shellholder and then another eighth of a turn—per Redding’s instructions—before securing the lock ring in place. Premium reloading tools that cost a bit extra are worth every dollar.

Redding’s lube container states “apply sparingly,” and that’s just what it means. I rub my forefinger over the lube gel and—sparingly—wipe my fingertips around the case head and up to just below the shoulder. I quickly learned to avoid allowing any lube to touch the shoulder or neck or I’d get an ugly dent in the case shoulder. If you refit the decapping/expander rod with a carbide expander plug, you don’t need to apply lube inside the case neck before sizing; however, I would still dry brush the necks before sizing to remove any powder residue. I also clean and uniform the primer pockets just to be sure the primers will seat securely just below flush. To ensure the most precise range results for both accuracy and velocity, I dispensed each powder charge with an RCBS electronic powder measure and then weighed each charge on another digital scale. According to Webster’s dictionary, myriad means “a whole lot,” whereas plethora means “quite a few.” Until just a few years ago, scarce would best describe the number of 6.5/.26-caliber rifle bullets available to reload. Today, there’s at least a plethora of excellent choices for hunting and competition. For this exercise, I tested bullets weighing from 120 to 156 grains, including conventional cup-and-core, bonded, and monolithic designs. Hodgdon’s test loads were developed with Federal 215 Large Rifle Magnum primers, so that’s what I used.

Range Results

Weatherby guarantees three-shot, sub-MOA groups fired from a cold barrel with Weatherby or other premium ammunition. My Mark V Accumark met that mark during the first three range sessions. And using Hodgdon’s pressure-tested data as a guide, almost half of my handloads also achieved that very tough performance objective. If you’re a stubborn, old-fashioned, blue-steel-and-walnut-only rifle loony, the Mark V Accumark may not strike your fancy. It has a stainless, graphite black Cerakoted action with matching Cerakote accents in the 24-inch fluted stainless barrel. The hand-laid fiberglass Monte Carlo-style stock is matte gel-coated with spiderweb accents. In other words, it’s the most modern-looking rifle on the rack. The 54-degree bolt throw will clear most low-mounted riflescopes. (I mounted a Leupold VX-5HD 3-15X 44mm in lightweight Talley mounts on my rifle for this report.) The TriggerTech trigger exhibits zero creep and minimum overtravel, and it is externally adjustable. My rifle’s trigger pull measured 3.25 pounds and was consistent from shot to shot. An Accubrake ST muzzle brake is included with the rifle to accommodate a recoil-sensitive shooter. It was easy to install and stayed securely in place throughout all of the several range sessions. The 6.5 Weatherby RPM cartridge is sized to fit Weatherby’s scaled-down, standard-length, six-lug Mark V action, and the rifle’s magazine holds three rounds.

For each test load, I loaded 10 rounds with a conservative mid-to-upper-range charge of Hodgdon or IMR propellant and one of several component bullets. I fired a couple three-shot groups at 50 yards and one group at 100 yards to determine which showed promise. Groups measured from 0.125 inch up to an inch. I winnowed down my selections and, if indicated by comparing the velocity data with Hodgdon’s lab data, adjusted the charge weight. Then I fired two additional three-shot groups at 100 yards for record. Just for grins, I loaded a few of the same 6.5 Weatherby RPM recipes in 264 Winchester Magnum cases and fired them in my 1963-vintage Remington Model 700 ADL Deluxe to compare ballistic performance. The Model 700 also has a 24-inch stainless barrel (still in good condition), but it does not have a muzzle brake. It’s a couple pounds heavier, so the recoil was comparable. Sure enough, velocities were 50-plus fps slower, just as I expected, but the old 264 Winchester Magnum gave a good account of itself downrange. Winchester introduced three belted magnum rounds in the late 1950s. Coincidentally, the calibers were all different (.458, .264, and .338) from the then-existing Weatherby Magnums. These were the first belted rounds offered by any of the major domestic ammunition manufacturers. The 264 Winchester Magnum is modestly overbore for caliber, i.e., like the Weatherby Magnums. Winchester, however, didn’t incorporate the signature double-radii, venturi-shaped shoulder and extended neck.

In response to Winchester’s foray into Magnum rounds, Weatherby soon introduced the 340 Weatherby Magnum and the 460 Weatherby Magnum that surpassed the ballistics of the corresponding Winchester belted rounds. Weatherby also experimented with a 6.5-300 Magnum, but likely due to a lack of interest in that caliber, he did not release it. As mentioned earlier, Roy’s son, Ed, finally released it many years later. The 6.5-300 Weatherby is significantly overbore and easily claims the “fastest .26-caliber cartridge” honors. The new 6.5 Weatherby RPM is the first Weatherby Magnum designed without the belted case and double-radii, venturi-shaped neck. The 6.5 Weatherby RPM case has a rebated rim (30-06 size), half-inch-diameter case head, 35.25-degree shoulder, and one-caliber-length neck. Actually, the 6.5-284 Norma shares almost identical case dimensions, except the 6.5 Weatherby RPM case is about 0.400 inch longer. In my opinion, the 6.5 Weatherby RPM is more refined than the 6.5-300 Weatherby, providing efficient and quite adequate ballistic performance with less wear and tear on the rifle and rifleman. And my experience with both rounds leads me to conclude the 6.5 Weatherby RPM is today’s improved-technology version of the decades old 264 Winchester Magnum. Why do I say this? First, usable case capacity is approximately 82 grains of water—just a bit short of the 264 Winchester’s. The superfluous belt is gone, and although the case body diameter is a bit less, it’s also a little longer and almost straight. The 6.5 Weatherby RPM’s more abrupt shoulder ensures proper and repeatable headspace and also minimizes case stretch when the round is fired. S.A.A.M.I. max MAP for the 264 Winchester Magnum is 64,000 psi compared to 65,000 psi for the 6.5 Weatherby RPM. Both are standard 30-06 length (3.340 inches max). Today’s much improved and slower burn-rate propellants, e.g., IMR 7977, IMR 8133, Hodgdon Retumbo, and H1000, allow the 6.5 Weatherby RPM to achieve better ballistic performance than the 264 Winchester Magnum could 60-plus years ago.

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