Weatherby 338 WBY RPM 225gr Interlock Ammunition

Weatherby 338 WBY RPM: Precision Magnum Performance

Introduced in 2022, the 338 WBY RPM (Rebated Precision Magnum) represents a thoughtful marriage of power and practicality. Weatherby engineered this cartridge to maximize the potential of the lightweight Mark V 6 Lug action—delivering magnum performance in a rifle light enough for serious backcountry hunting.

Design and Development

The 338 RPM is based on the 6.5 RPM necked up to accept .338 caliber bullets. This foundation provides:

• Large body diameter for increased powder capacity
• Low body taper for efficient case design
• 35-degree shoulder that creates additional internal volume
• Higher velocities than conventional .338 magnums in comparable rifle weights

Ammunition Specifications

This Weatherby Select Plus load pairs the proven 338 WBY RPM case with Hornady Interlock bullets:

• Bullet Weight: 225 grains
• Muzzle Velocity: 2800 fps
• Casing: Reloadable brass
• Package: 20 rounds per box
• Manufacture: USA-made

Purpose and Application

The 338 WBY RPM was conceived with a clear mission: to fit a large caliber bullet into a lightweight rifle capable of taking all of North America's big game. The Interlock bullet design provides reliable expansion and deep penetration—essential characteristics for ethical, effective hunting at extended ranges.

This is ammunition for the serious hunter who refuses to compromise between power and portability.