The 6.5 WBY RPM (Rebated Precision Magnum) is based on the lengthened version of the .284 Winchester. The large body diameter low body taper and 35-degree shoulder mean that case capacity is greatly increased leading to higher velocities. – CARTRIDGE SPECS – Bullet Diameter: .264 (6.5mm) – Common Reference: 6.5mm Caliber – Max Case Length: 2.57 – 156 Grain Berger Elite Hunter