257 Weatherby Magnum

Technical Specifications

 

Country of Origin United States
Diameter – Bore .250” (6,35mm)
Diameter – Groove .257”€ (6,53mm)
Introduced 1944
Pressure – Max Average 62,500 psi SAAMI (440 MPa – CIP)
Regulators SAAMI & CIP
Groove Details 6 x .098” (2,49mm)
Shellholder – RCBS 4
Twist – Proof Barrel 1:10” (254mm)
Cartridge Essentials

 

Action Size Recommended Standard length & magnum bolt face
Barrel Life 1,200 – 1,400 rounds
Case – Body Taper .63°
Case – Neck Length .3906” (9,92mm) = 151.9%
Case – Trim Length 2.541”€ (64,30mm)
Parent Case .300 H&H
Relative Capacity 84.0 gr water (5,454 cc)
Shoulder Angle 50°52’39.5”€€ double radius
Typical Factory Load Guidelines for
Brand Name Bullet Weight Bullet Description Velocity Fps Energy Ft/Lb Trauma Potential 100% Expansion
Nosler 120-gr Nosler Partition 3,135 fps 2,619 ft/lb 40.1
Weatherby 120-gr Nosler Partition 3,305 fps 2,911 ft/lb 44.6
Weatherby 117-gr Hornady RN 3,402 fps 3,008 ft/lb 46.1
Nosler 115-gr Ballistic 3,250 fps 2,698 ft/lb 41.3
Nosler 115-gr Nosler Partition 3,250 fps 2,698 ft/lb 41.3
Weatherby 115-gr Nosler Ballistic Tip 3,400 fps 2,953 ft/lb 45.2
Hornady 110-gr Hornady Interbond 3,330 fps 2,709 ft/lb 41.5
Nosler 110-gr Nosler Accubond 3,400 fps 2,824 ft/lb 43.3
Weatherby 110-gr Nosler Accubond 3,460 fps 2,925 ft/lb 44.8
Optimum Game Bullet Optimum Bands (120-gr averaged)
Band Velocity Parameters Start End
Red-Band ( > 2,600 fps) 0 yds ± 260 yds
Green-Band ( ≤ 2,600 fps – ≥ 2,200 fps) ± 260 yds ± 425 yds
Amber-Band ( ≤ 2,200 fps – ≥ 2,000 fps ) ± 425 yds ± 500 yds
Bullet Recommendations for Africa
Antelope : Premium fifth generation to seventh generation bullets
African Game Weight Recommendation
≤ 260-lb (≤ 120-kg)
Most Suitable African Species (assuming legality)
Small Game : Arabian oryx, addax, antbear, baboon, blesbok, bontebok, bushbuck, bushpig, cheetah, hyena, impala, leopard, puku, rhebok, reedbuck, sitatunga, springbok and . Power wise it is also suitable for species such as bushbuck, but the latter is not listed as this is a long-range cartridge and the species is hunted at point blank range.
* Read all about these animals in the book Game Animals of the World by Chris & Tilde Stuart
Optics Guidelines
Eye Relief Non critical
Exit Pupil ≤ 2.5mm
Magnification: Red-Band ≥ 9x – ≤ 10x
Magnification: Green-Band ≥ 10x – ≤ 18x
Magnification: Amber-Band ≥ 18x – ≤ 24x
Objective Lens ≥ 50mm – ≤ 56mm
Parallax Adjustability Yes
Reticules Fine with ranging bars
Handloading Guidelines
Load Development 0.5 grain increments
Primer Magnum Large Rifle
Propellant Range Ultra-slow rifle : ≥ Hodgdon H-4350 – ≤Hodgdon H-870
Tips Engage in precision handloading techniques