257 Weatherby Magnum History and General Information.  The 257 Weatherby Magnum was introduced to the public in the mid 1940's by Roy Weatherby as one of his original cartridges and his personal favorite as well.  The 257 Weatherby Magnum cartridge case itself is the 300 H&H magnum case necked down to 25 caliber and blown out the full length of the case which then sports a double radius shoulder and shortened to 2.545" with a long neck.  The 257 Weatherby Magnum is a extremely flat shooting dual purpose cartridge and is the fastest of all commercially available 25 caliber cartridges, sending a 75 grain bullet out the muzzle at 3,900 feet per second for varmints and able to send a 115 grain bullet out the muzzle at 3,400 feet per second for deer sized game.  The 257 Weatherby Magnum with the power it offers down range will also recoil somewhat to the shooters shoulder but is still manageable to shoot. The 257 Weatherby Magnum definitely needs a 26" barrel length for a more complete powder burn as the muzzle blast and flash are fairly high.   257 Weatherby Magnum Barrel Specifications. Common Barrel Twist Rate - 1/12 - 1/10 Bore Groove Diameter - .257"   257 Weatherby Magnum Reloading Specifications. Bullet Diameter - .257" Maximum Case Length - 2.550" Trimmed Case Length - 2.540" Primer Size - Large Rifle   257 Weatherby Magnum Loading Data Hints.  The 257 Weatherby Magnum responds well to slower burning powder such as i.m.r. 4350 and 4831, when using heavier 117 to 120 grain weight bullets check the rifling twist rate of your rifle as the earlier rifles had a 1 in 12" twist and will not adequately stabilize them. 257 Weatherby Magnum Reloading Data. Hodgdon Reloading Data Center.   257 Weatherby Magnum Trajectory and Hunting Applications.  This is a down range trajectory chart for the 257 Weatherby Magnum cartridge with the scope mounted 1.5 inches above the bore center line plus if you were using this load, its effective hunting bullet energy range with well placed shots on, Varmint / Predator size game, such as Bobcat, Cougar, Coyote. Deer size game, such as Antelope, Blacktail, Hogs, Javelina, Mule, Whitetail. Elk size game, such as Caribou, Black Bear, Sheep. Moose size game, such as Brown Bear. Bullet diameter .257" Bullet weight 100 grains Bullet ballistic coeffecient .357 Bullet velocity 3,600 feet per second Range 100 yds. 200 yds. 300 yds. 400 yds. 500 yds. + + .9 0 - 4.7 - 14.3 - 29.7 2417 2016 1668 1369 1117  Varmint + + + + + +  Deer + + + + - -  Elk + + - - - -  Moose + - - - - - Copyright 2001 - 2010