.270 Weatherby Magnum

The .270 Weatherby Magnum was the first belted magnum based on the .300 H&H Magnum to be developed by Roy Weatherby in 1943.[2] The cartridge is short enough to function in standard-length long actions with a brass length of 2.549" or 64.74mm and an overall length of about 3.295".[2]

.270 Weatherby Magnum
.270 Weatherby 2nd from left
TypeRifle / Hunting
Place of originUSA
Production history
DesignerRoy Weatherby
Designed1943
ManufacturerWeatherby
Specifications
Parent case.300 H&H Magnum
Case typeBelted, bottleneck
Bullet diameter.277 in (7.0 mm)
Neck diameter.303 in (7.7 mm)
Shoulder diameter.492 in (12.5 mm)
Base diameter.512 in (13.0 mm)
Rim diameter.531 in (13.5 mm)
Rim thickness.220 in (5.6 mm)
Case length2.55 in (65 mm)
Overall length3.25 in (83 mm)
Rifling twist1-10"
Primer typeLarge rifle magnum
Ballistic performance
Bullet mass/type Velocity Energy
110 gr (7 g) HP 3,528 ft/s (1,075 m/s) 3,041 ft⋅lbf (4,123 J)
130 gr (8 g) X 3,338 ft/s (1,017 m/s) 3,217 ft⋅lbf (4,362 J)
140 gr (9 g) BT 3,242 ft/s (988 m/s) 3,268 ft⋅lbf (4,431 J)
150 gr (10 g) SBT 3,161 ft/s (963 m/s) 3,329 ft⋅lbf (4,514 J)
Test barrel length: 26"
Source(s): Accurate Powder [1]

History and Design

The development of the .270 Weatherby Magnum led to the characteristic double-radius shoulders belted magnum case, proprietary of the Weatherby Magnum line of cartridges. Particularly, the .270 Wby Mag the result of necked down to accommodate the .277 in bullets and bringing down the case to fit a standard length action.[3] Like most Weatherby cartridges, the .270 Weatherby was standardized by the Small Arms and Ammunitions Manufacturers Institute in 1994, and it has a SAAMI maximum pressure limit of 62,500 psi. The first Weatherby cartridge to be used in Africa was the .270 Weatherby on a jackal on June 8, 1948.[4]

Performance

Given its higher pressure and larger case which holds more powder than the .270 Winchester, the .270 Weatherby has about 200 ft/s faster performance with any particular bullet weight.[5] It also outperforms newer cartidge designs such as the .270 WSM and the 6.8 Western. This performance comes at the cost of more recoil and barrel heat. In addition, a long barrel is necessary to take advantage of extra powder to gain maximum velocity. The cartridge is excellent at long-range hunting, but is not well suited to high-volume shooting such as varmint hunting.[6]

For those handloading their own cartridges, this is an easy round to load. It does best with full-power loads and is not well-suited for reduced loads.[6][7] Ed Weatherby, son of Roy Weatherby says that the .270 Weatherby is his favorite caliber. As he puts it, there just isn't a better long-range deer caliber. He goes on to mention that it is also quite effective for elk, and pronghorn.[4]

Sporting Use

Due to its flat trajectory result of a combination of a high muzzle velocity and ballistic coefficient, the .270 Wby Mag makes an excellent cartridge option for mid sized big game out to considerable ranges and the fact of being chambered in standard length actions allows the possibility of manufacturing a light mountain rifle.[8]

.308 Winchester (left) .270 Weatherby Magnum (center) .223 Remington (Right)

See also

References
  1. ".270 Weatherby data from Accurate Powder" (PDF). Archived from the original (PDF) on 2007-09-28. Retrieved 2007-08-18.
  2. Bullets, Speer (2009). Speer Bullets Reloading Manual #14. Speer. p. 340. ISBN 978-0-9791860-0-4.
  3. Carter, Aaron (March 5, 2015). ".270 Wby. Mag.: The Original Weatherby". americanrifleman.org.
  4. Nosler, Inc. (2002). Nosler Reloading Guide (5th ed.). Bend, OR, USA: Nosler, Inc. pp. 219–224.
  5. Sillars, Jordan (April 21, 2022). "CALIBER BATTLE: .270 WBY. MAG. VS. .270 WIN".
  6. Barnes, Frank C. (2006) [1965]. Skinner, Stan (ed.). Cartridges of the World (11th ed.). Iola, WI, USA: Gun Digest Books. p. 43. ISBN 0-89689-297-2.
  7. Ackley, P.O. (1927) [1962]. Handbook for Shooters & Reloaders. vol I (12th Printing ed.). Salt Lake City, Utah: Plaza Publishing. pp. 384, 385. ISBN 978-99929-4-881-1.
  8. ".270 Weatherby Magnum". Terminal Ballistic Studies.
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