Now available: The new .338 Weatherby Rebated Precision Magnum cartridge (338 WBY RPM)

An ideal backcountry large game round designed for North America’s biggest game, including elk, bear and moose: Weatherby adds the new .338 Weatherby Rebated Precision Magnum (338 WBY RPM) to its pretty long list of ultra-high velocity, magnum cartridges that already includes classics such as the .300 Weatherby Magnum, .340 Weatherby Magnum and the .270 Weatherby Magnum. After being accepted by SAAMI a few months ago, the 338 WBY RPM is finally available, together with the new rifles chambered in it. “I am excited to announce the second cartridge in the Weatherby RPM family. It was a long time coming due to demand and supply chain delays, but I believe it will be worth the wait!”, says Adam Weatherby. 

Video: First Animal Taken by the 338 WBY RPM ammuniton

New caliber: 338 WBY RPM cartridge and rifles

The .338 WBY RPM is offered in four bullet options.

The RPM case was purpose built for the smaller Mark V six-lug action to offer magnum performance in a lightweight package, and “upon the launch of the 6.5 WBY RPM in 2019, we began to dream of what could be next in the RPM family. Having successfully launched a 5 lb rifle in a 6.5 caliber magnum cartridge, I began to imagine what it would be like if we had a big bore option that could fit in the same Weatherby Mark V 6 lug action”.

338 WBY RPM SAAMI cartridge case specs. 

Field testing for the 338 WBY RPM began back in 2020. Now, the .338 WBY RPM is offered with the following bullets: 225-gr Nosler Accubond, 225-gr Hornady Interlock, 180-gr Barnes TTSX and .225-gr Barnes TTSX. Rim and base diameters are the same as the .284 Winchester, but maximum average pressures are higher (65,000 psi instead of 56,000 psi).

The Mark V Backcountry 2.0 Ti rifle with 20” barrel. A perfect fit for  the new caliber: 338 WBY RPM 

Weatherby already offers rifles chambered for the new cartridge: for example, the short Backcountry 2.0 Ti with 18” barrel, featuring a Peak 44 Blacktooth Carbon fiber stock, a 3DHex recoil pad, TriggerTech trigger, and 53 degree bolt throw for faster chambering on follow-up shots and greater bolt-to-scope clearance. Other rifle models chambered for the 338 WBY RPM will include: Backcountry 2.0 - 18” #3 Contour Steel Barrel, Backcountry 2.0 Carbon - 20” #4 Contour BSF Carbon Barrel, Backcountry 2.0 Ti Carbon - 20” #4 Contour BSF Carbon Barrel, Accumark - 24” #3 Contour Steel Barrel, Carbonmark- 24” #4 Contour BSF Carbon Barrel.

“I am truly honored to be able to carry on my grandfather’s legacy of cartridge development and rifle building. The pairing of this new cartridge with our latest rifles reminds me of one of his old slogans that said 'Tomorrow’s Rifles Today.' I only wish he could be here to see the innovation and development that our amazing Sheridan-based team is able to accomplish,” concludes Adam Weatherby.

.338 Weatherby Rebated Precision Magnum ammo: ballistic data