The Weatherby 338 WBY RPM 225gr InterLock load is a box of 20 rounds of 338 WBY RPM hunting ammunition built on premium brass (Weatherby part no. H338225IL). Weatherby describes the 338 WBY RPM (Rebated Precision Magnum, introduced in 2022) as the 6.5 RPM case necked up to take a .338 bullet, designed to pull magnum performance out of the Mark V 6-Lug action in a rifle of about five pounds. The Hornady InterLock has an exposed lead tip for controlled expansion on a secant ogive, and a raised ring inside the jacket locks the jacket to the one-piece core so the bullet retains mass and energy. Weatherby publishes a muzzle velocity of 2,800 fps and 3,917 ft-lbs of muzzle energy for this 225-grain load, still carrying 1,771 fps at 500 yards. The large body diameter, low body taper and 35-degree shoulder increase case capacity and drive higher velocities, and Weatherby says the cartridge holds its velocity even from the 18-inch barrels on its Mark V Backcountry rifles.

Key Specifications

• The cartridge is 338 WBY RPM, a rebated precision magnum built on the 6.5 RPM case necked up for .338 bullets.
• Bullet weight is 225 grains, the load weight Weatherby lists for this part number.
• The bullet is the Hornady InterLock, and the locked jacket and core keep the bullet together as it expands.
• Bullet diameter is .338 inch (8.6mm), the size Weatherby lists for this cartridge.
• The G1 ballistic coefficient is .397, a measure of how well the bullet resists drag as it flies.
• Muzzle velocity is 2,800 fps from Weatherby published ballistics, which sets the flatness of the trajectory.
• Muzzle energy is 3,917 ft-lbs, the starting point for the energy the bullet delivers downrange.
• Velocity at 500 yards is 1,771 fps, showing how much speed the bullet retains at long range.
• Maximum case length is 2.57 inches, the dimension that governs which chamber the round fits.
• The case is premium brass, which Weatherby pairs with carefully selected powder and primers for consistent ignition.

Frequently Asked Questions

What bullet does this 338 WBY RPM load use? It uses a 225-grain Hornady InterLock. The Hornady InterLock has an exposed lead tip for controlled expansion on a secant ogive, and a raised ring inside the jacket locks the jacket to the one-piece core so the bullet retains mass and energy.

What velocity and energy does this load publish? Weatherby lists 2,800 fps and 3,917 ft-lbs at the muzzle, falling to 2,356 fps and 2,773 ft-lbs at 200 yards and 1,771 fps and 1,567 ft-lbs at 500 yards.

What is the 338 WBY RPM cartridge? Weatherby describes the 338 WBY RPM (Rebated Precision Magnum, introduced in 2022) as the 6.5 RPM case necked up to take a .338 bullet, designed to pull magnum performance out of the Mark V 6-Lug action in a rifle of about five pounds. The large body diameter, low body taper and 35-degree shoulder increase case capacity and drive higher velocities, and Weatherby says the cartridge holds its velocity even from the 18-inch barrels on its Mark V Backcountry rifles.

Buy the Weatherby 338 WBY RPM 225gr Hornady InterLock Rifle Ammunition, 20-Round Box

Weatherby builds this 338 WBY RPM load around a 225-grain Hornady InterLock so the cartridge performs the way its design intends. Order it from Weatherby‘s selection of rifle ammunition through our Lubbock, Texas gun shop for fast, insured shipping.