The Weatherby 257 WBY Mag 100gr Swift Scirocco load is a box of 20 rounds of 257 Weatherby Magnum hunting ammunition built on premium brass (Weatherby part no. F257100SCO). Weatherby says the 257 Weatherby Magnum was one of the earliest creations of Roy Weatherby, developed in 1943 and in production from 1945, and that it quickly became his favorite. The Swift Scirocco is a bonded bullet with signature black tips, built for hunting and long-range efficiency, with a progressively tapered pure copper jacket that controls expansion and is bonded to the core. Weatherby publishes a muzzle velocity of 3,575 fps and 2,838 ft-lbs of muzzle energy for this 100-grain load, still carrying 2,443 fps at 500 yards. The company describes this flat-shooting cartridge as one of its most popular rounds.

Key Specifications

• The cartridge is 257 Weatherby Magnum, one of the earliest Weatherby cartridges and a favorite of Roy Weatherby himself.
• Bullet weight is 100 grains, the load weight Weatherby lists for this part number.
• The bullet is the Swift Scirocco, and bonding the jacket to the core is how it holds together on impact.
• Bullet diameter is .257 inch (6.35mm), the size Weatherby lists for this cartridge.
• The G1 ballistic coefficient is .429, a measure of how well the bullet resists drag as it flies.
• Muzzle velocity is 3,575 fps from Weatherby published ballistics, which sets the flatness of the trajectory.
• Muzzle energy is 2,838 ft-lbs, the starting point for the energy the bullet delivers downrange.
• Velocity at 500 yards is 2,443 fps, showing how much speed the bullet retains at long range.
• Maximum case length is 2.549 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 257 WBY Mag load use? It uses a 100-grain Swift Scirocco. The Swift Scirocco is a bonded bullet with signature black tips, built for hunting and long-range efficiency, with a progressively tapered pure copper jacket that controls expansion and is bonded to the core.

What velocity and energy does this load publish? Weatherby lists 3,575 fps and 2,838 ft-lbs at the muzzle, falling to 3,085 fps and 2,113 ft-lbs at 200 yards and 2,443 fps and 1,325 ft-lbs at 500 yards.

What is the 257 WBY Mag cartridge? Weatherby says the 257 Weatherby Magnum was one of the earliest creations of Roy Weatherby, developed in 1943 and in production from 1945, and that it quickly became his favorite. The company describes this flat-shooting cartridge as one of its most popular rounds.

Buy the Weatherby 257 WBY Mag 100gr Swift Scirocco Rifle Ammunition, 20-Round Box

Weatherby builds this 257 WBY Mag load around a 100-grain Swift Scirocco 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.