The 338 WBY RPM (Rebated Precision Magnum) is based on the Weatherby 6.5 RPM necked up to accept a 338 caliber bullet. The 338 RPM was designed to take advantage of Weatherby 6-Lug action to get magnum performance in a 5lb rifle. The large body diameter, low body taper, and 35-degree shoulder mean that case capacity is greatly increased, leading to higher velocities.
