Weatherby 6.5 RPM Cartridge Review

The all-new 6.5 Weatherby Rebated Precision Magnum (WBY RPM) cartridge is a vast departure from classic Weatherby design. The 6.5 WBY RPM has no belt, no double-radius shoulder, and no freebore. It’s still a hotrod, but that’s about all it has in common with its traditional belted-magnum, Venturi-shouldered, generously freebored ancestors.

The cartridge has a steep, 35.25-degree shoulder, nearly parallel sides, and a rebated rim. For those of you familiar with the 6.5-284 Norma, imagine a stretched-out version that makes the most of a long rifle action, provides magnum 6.5mm ballistics, and is compatible with a standard 0.473-inch-diameter (.30-06 size) boltface.

So, what inspired this dramatic departure from traditional Weatherby engineering? The 6.5 WBY RPM cartridge was designed for a new, sub-five-pound mountain rifle built on a titanium version of the company’s slender six-lug Mark V action. Titanium is another first for Weatherby. There are only a couple of centerfire rifle actions in existence that are this slender, and before the 6.5 WBY RPM, no magnum cartridge fit and functioned in any of them because the boltfaces of petite actions are not big enough in diameter to handle traditional magnum cartridge case heads. Thus, the rebated rim of the 6.5 WBY RPM.

Backcountry hunters love sleek, lightweight rifles. They also love accurate magnum cartridges with extended reach. However, prior to this, it was difficult to find both in one package without paying a jaw-dropping amount for a full-on custom rifle.

Previously, the best way to get serious magnum performance in an extremely lightweight backcountry rifle was to opt for a short action made of titanium and chambered for cartridges like the 6.5 PRC, 7mm SAUM, or .300 WSM. However, actions adequate for such cartridges are still beefy in diameter and difficult to finesse into a sub-five-pound rifle.

Weatherby reasoned that as long as the six-lug Mark V’s boltface retained the 0.473-inch size, it would be possible to massage the magazine feed lips into functioning with a larger body diameter, effectively pairing magnum performance with wand-like lines and balance. It works. These new Mark V Backcountry rifles are incredibly svelte and shoot 130-grain 6.5mm bullets in excess of 3,300 fps.

Ballistics

By the time you read this, Weatherby will have introduced three factory loads for the 6.5 WBY RPM: a 127-grain Barnes LRX at around 3,300 fps, a 140-grain Hornady InterLock at about 3,100 fps, and a 140-grain Nosler AccuBond at around 3,100 fps. The Nosler and Barnes bullets are premium, controlled-expansion projectiles at a price of about $65 per box of 20; the Hornady InterLock is a more cost-effective cup-and-core bullet at about $50 per box of 20.

For comparison’s sake, that’s more velocity than can be expected from traditional 6.5 magnums, such as the .264 Winchester Magnum, or from popular modern high-performance 6.5 selections like the 6.5 PRC and 6.5-284 Norma. It’s considerably less than is generated by the 26 Nosler and Weatherby’s 6.5-300 (the fastest factory 6.5mm cartridge in existence). However, the latter two are in a different speed zone altogether. (See the accompanying case-capacity chart for a comparison.)

The 6.5 WBY RPM produces enough velocity that it’s worth zeroing at 300 yards, particularly with the zesty velocity of the 127-grain LRX factory load. In standardized, sea-level atmospheric conditions, it will impact about 2.6 inches high at 100 yards, 3.4 inches high at 200 yards, dead-on at 300 yards, and just 8.3 inches low at 400 yards. For those who like to be prepared for fleeting shot opportunities out to a quarter-mile, that’s a really useful trajectory.

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It’s worth noting, too, that this load generates over 3,000 ft-lbs of muzzle energy. Even in the dense air at sea level, it maintains the conventional minimum for elk (1,500 ft-lbs) to about 500 yards and the commonly accepted minimum for deer (1,000 ft-lbs) out to 750 yards.

For this article, Weatherby marketing guru Kevin Wilkerson was kind enough to send me two prototype 6.5 WBY RPM loads—featuring the Nosler and Barnes bullets—and one of only two reloading die sets in existence. After test-firing the prototype factory ammo, I handloaded and tested four additional bullets, including Berger’s 140-grain VLD Hunting, Sierra’s 130-grain GameChanger, Hornady’s 143-grain ELD-X, and Swift’s 120-grain A-Frame.

Because the cartridge was still embryonic at the time and no reloading data was available, I mirrored the propellant charges and primer choice used in the prototype factory ammunition. Cases loaded with bullets in the 140-grain range got 64 to 66 grains of Reloder 25, and loads for the lighter bullets received charges of 66 to 68 grains of the same powder. Federal’s Gold Medal Large Rifle 210 primers were used in all handloads because that’s the primer Weatherby had found best results with in the prototype ammo.

Even though it resulted in ammunition too long to feed through from the magazine, I seated the Berger and Sierra bullets out to lightly contact the rifling leade. I’d never been able to do that with a factory Weatherby chamber before due to the traditionally long freebore, and I just wanted to try it.

I single-loaded the cartridges while accuracy testing. Apparently, it didn’t result in a tangible benefit; to my surprise, the Berger load was the least accurate tested in the lightweight Mark V Backcountry Ti rifle. The Sierra GameChanger, on the other hand, averaged sub-MOA. Two magazine-length handloads featuring Hornady’s ELD-X and Swift’s A-Frame also averaged sub-MOA.

Weatherby 6.5 RPM Cartridge Specs

Water Capacity: 82.5 grs. (as measured)
Overall Case Length: 2.570 in.
Trim-To Case Length: 2.560 in.
Cartridge Overall Length: 3.340 in.
Primer: Large Rifle or Large Rifle Magnum
Max Pressure: 64,000 psi

The Rifle

Speaking of the rifle, the new Mark V Backcountry Ti isn’t your granddaddy’s Weatherby. It has a straight-comb stock rather than the classic Monte Carlo cheekpiece. The lines of the grip and the fore-end nose are distinctly different as well.

However, the heart of the rifle—its action—is pure bull-strong, glass-smooth Weatherby but with a new twist. As mentioned earlier, the action is made of super-light titanium. This is a first for Weatherby. As you may know, titanium is expensive and wickedly difficult to machine. The significant reduction in weight is deemed worth the effort, but only you can decide whether it’s also worth the $1,000 increase to the price. (Don’t worry because you do have a choice: Weatherby is also making a steel-action version of the Mark V Backcountry.)

Several characteristics set the six-lug Mark V action apart. Foremost, it is small in diameter and slender. The result is it is light in weight. Next is the lockup, which—as you may have guessed—comprises six different lugs that interface with the receiver. Not only does this design provide a fast, 54-degree bolt throw, but also it provides plenty of metal-on-metal contact between the bolt lugs and the action. That’s not a big deal with all-steel actions, but it is with titanium actions.

You see, titanium has a couple of bad habits. It tends to gall if it gets too dry or too dirty. Worse, it “coins,” which is basically peening—or flattening—caused by the repeated hammering blows of high-pressure cartridges detonating. Over time and too many max-pressure rounds, this can, in some cases, cause headspace to increase to the point where accuracy is lost and safety is compromised.

Although each Mark V lug is individually smaller than any lug on a traditional dual, opposing-lug action, collectively all six offer an admirable amount of contact surface, effectively reducing the coining potential.

It’s worth noting that even titanium actions have chrome-moly steel bolts, which are given a Graphite Black Cerakote finish. Deep spiral flutes in the bolt body keep weight to a minimum. A rocker-type two-position safety is mounted on the bolt shroud.

Mark V Backcountry stocks are premium carbon fiber made by AG Composites, using a proprietary process that “provides excellent stiffness and lightweight attributes,” according to company literature. A vastly different break from the Weatherby norm is the 3D Hex recoil pad. It weighs measurably less than common foam-rubber pads, and it has a patent-pending, high-strength, energy-diffusing lattice structure designed to distribute specific directional forces and diminish muzzle lift. It works, and it and the muzzle brake combine to make the ultralight Backcountry 6.5 WBY RPM recoil about like a .243 Winchester rifle.

Now, you might be thinking that in a sub-five-pound rifle even a 6.5mm round could kick pretty noticeably, particularly a magnum 6.5. Well, yes. However, each rifle comes fitted with Weatherby’s Accubrake ST, which reduces felt recoil by up to 53 percent. It’s turned to the same barrel diameter, so it’s sleek and looks great. Each rifle comes with a thread protector, too, for those who prefer to hunt without a brake.

The trigger is by TriggerTech and is user-adjustable from 2.5 to 5 pounds in pull weight. According to my Lyman digital trigger gauge, the sample rifle’s trigger pull measured 3 pounds, 1 ounce, with just 1.5 ounces of variation over a series of five measurements.

Lastly and importantly, each Mark V Backcountry rifle comes with a sub-MOA accuracy guarantee.

Weatherby Mark V Backcountry TI Rifle Specs

Manufacturer: Weatherby; weatherby.com
Type: Bolt-action repeater
Magazine Capacity: 3 rounds
Barrel Length: 24 in.
Overall Length: 46 in.
Weight, Empty: 4.94 lbs.
Stock: Carbon fiber
Length of Pull: 14 in.
Finish: Raw titanium action, Graphite Black Cerakote barrel and action
Sights: None; receiver drilled and tapped for scope mounts
Trigger: 3.06-lb. pull (as tested)
Safety: Two position
MSRP: $3,500

Field Performance

Knowing I’m a mountain-hunting nut case (and the host of the “Backcountry Hunting Podcast”), Adam Weatherby extended an invitation to hunt northwestern Montana spring black bear. We took two prototype Mark V Backcountry Ti rifles with titanium actions. Adam used the 140-grain AccuBond prototype factory load, and I used handloaded ammunition featuring Hornady’s 143-grain ELD-X.

Over the course of four days, we covered 32 miles with loaded packs, much of it bushwhacking through steep country and dense underbrush. Adam took his bear the first evening, putting his first shot squarely through the vitals at a bit more than 400 yards, then following it up with a couple more to ensure it didn’t escape into the brush-choked creek bottom. Three days and an almost-vertical four-hour climb later, I went prone on a steep slope and shot a mature color-phase bear bedded about 220 yards distant. The Hornady ELD-X quartered through it, turning the vitals to mush.

Had I been carrying a standard-weight hunting rifle rather than the lightweight Mark V Backcountry Ti, the climb would have been exponentially more difficult. It was the sort of shockingly hard stalk that even serious backcountry hunters may only do a few times in their life and the sort that brings out the real virtues of a true mountain rifle.

Back in January of this year, Weatherby announced it was moving its headquarters from Paso Robles, California, to Sheridan, Wyoming, after 73 years in the Golden State. The introduction of the new 6.5 WBY RPM and the Mark V Backcountry Ti titanium rifle demonstrate the company is headed in the right direction.