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THE .257 weatherby magnum: quarter-bore king: this prototype proprietary screamer still goes the distance against anything.

ROY WEATHERBY Roy E. Weatherby was the owner and founder of Weatherby, Inc., an American rifle, shotgun and cartridge manufacturing company set up in 1945. Weatherby firearms are best known for their very high-powered magnum rifle cartridges, such as the .257 Weatherby Magnum and the .  DEVELOPED THE.257 WEATHERBY MAGNUM IN 1948, and it fit the company's cartridge paradigm perfectly. It was inefficient, overbore capacity, had serious muzzle blast and caused fragile bullets to blow up on contact with game. The very low expansion ratio made it hard on barrels, and it took considerable increases in powder to get significant velocity gains. Consequently, it took a lot of heat early on from critics and sometimes still does.

All of that criticism is well placed. But let's get one thing straight right up front: None of it matters. The.257 Weatherby exists for one reason: as a long-range killing machine for antelope, deer and similar-size game. Period, Its flat trajectory and downrange down·range  
adv. & adj.
In a direction away from the launch site and along the flight line of a missile test range: landed a thousand miles downrange; the downrange target area. 
 potential are legendary and have been for decades.


In 1948 Roy went on his first African safari and killed more than 50 animals, many with his new.257. Even then Roy was a big proponent of high velocity "If you can get that small caliber [bullet] to disintegrate inside the animal, it will kill anything on the face of the earth," he wrote.

Weatherby offers a good selection of rifles chambered for the.257 WM. In addition to the top-of-the-line Mark V, the firm makes several models of the popular Vanguard, including the Synthetic, the Sporter and, reintroduced for 2012, the Sporter Deluxe--our test rifle this month. Weatherby guarantees 1 1/2-inch groups at 100 yards with proper ammunition, and we found this to be true. A new Trijicon 3-9x40 AccuPoint proved to be the perfect scope for it.

Test loads were prepared primarily with RCBS RCBS Rathfarnham Concert Band Society (Ireland)
RCBS Rock Chucker Bullet Swage (ammunition reloading company) 
 dies in a Redding Ultramag press, and an L.E. Wilson Adjustable Case Gauge was used to set the sizing die to barely set the shoulder back during resizing. This allowed the sized case to headspace head·space  
The volume left at the top of an almost filled jar, tin, or other container before sealing.

Noun 1. headspace - the volume left at the top of a filled container (bottle or jar or tin) before sealing
 on the shoulder rather than on the belt. This greatly prolongs case life and retards the development of incipient case-head separation. We also used an RCBS neck sizer, which aided case life (and was a work-saver because no case lube was required for its use).

The RGBS RGBS Red, Green, Blue, Composite Sync  set has a perfectly fine bullet seater, of course, but for these tests we used a Forster Ultra Micrometer-Style Bench Rest seater. This little gem has a sliding straight-line seater perched beneath a micrometer micrometer (mīkrŏm`ətər, mī`krōmē'tər).

1 Instrument used for measuring extremely small distances.
 thimble thimble,
n See coping.

thimble, ionization chamber,
n See chamber, ionization, thimble.
 that allows adjusting bullet-seating depth in.001-inch increments. The.257 WM is a recent addition to Forster's line of Bench Rest seaters, and it was a delight to use.


Roy Weatherby believed in giving the bullet a running start, so his rifles have prodigious free-bore--sometimes as much as 3/8 inch--and our test rifle was no exception. Everyone "knows" that for top accuracy you have to seat the bullet just short of the lands. Well, Weatherby must have missed that memo, because with the right ammo, virtually all Weatherbys shoot quite nicely, thank you. Our test rifle had plenty of free-bore, so we mostly seated bullets so that their bases were about even with the base of the neck, and everything went swimmingly (see the load table for the Cartridge Overall Length data). Early.257 WMs had 1:12 twists that would not stabilize long 117-to 120-grain bullets, but .257s are now made with 1:10 twists that will handle the heaviest .25-caliber bullets available.



The plump.257 Weatherby case is based on a shortened and blown-out.300 H&H Magnum case, but cases for reloaders and factory ammo are readily available. Trim length is 2.539 inches. All Weatherby cartridges have the unique double-radius shoulder. Rifle lore has it that this supposedly promotes a better flow of powder gases, but even Roy admitted that it was mostly for marketing.

Due to the relatively large amounts of slow-burning powders used by the cartridge, magnum primers are a good idea. My favorites are the Federal 215 (originally developed for the huge .378 Weatherby) and CCI CCI Chambre de Commerce et d'Industrie (France)
CCI CAM (Complementary and Alternative Medicine) Citation Index
CCI Chamber of Commerce and Industry (Western Australia) 
 250, although the Winchester LRM LRM Language Reference Manual
LRM Casa De Campo, Dominican Republic (Airport Code)
LRM Long Range Missile
LRM Line Replaceable Module
LRM Local Resource Manager
LRM Line-Reflect-Match
LRM Land Resources Management
 also worked very well in our tests. The maximum pressure for the .257 WM is 53,500 CUP.

Powder selection is likewise easy. Just look for the slowest-burning ones available from the manufacturer in question and you're pretty much set. Load data is available in all of the modern-day loading manuals. Most hunting-weight bullets do well with IMR IMR - Internet Monthly Report  7828, IMR 4831 or H-483L With lighter bullets, either H-4350 or IMR 4350 is just the ticket. From Alli-ant, Reloder 22 and Reloder 25 work best. Vihtavuori has several suitable numbers, including N-160, N-560 and N-165. Norma has MRP (Material Requirements Planning) An information system that determines what assemblies must be built and what materials must be procured in order to build a unit of equipment by a certain date.  and MRP-2 (soon to be replaced by No. 217). Ramshot Magnum and AA-3100, and Magpro from Accurate round out the lineup.

Bullet selection is a lot better than it was back in the day, with several tough bonded and monolithic designs. The Nosier Partition and several others effectively eliminate previous criticisms of the.257 WM for bullet blowups. While 75-, 87- and 90-grain bullets give high velocities, the.257 WM is first and foremost a big-game cartridge, so appropriate bullet selection really begins at 100 grains and continues on up to the 110-, 115-, 117-and 120-grainers. We tested more than 40 loads, and almost all performed well within Weatherby's accuracy guarantee. The best loads (in our test rifle) are shown in the load table, but if you don't see your favorite powder or bullet listed, don't hesitate to give them a try.

While the .257 WM is not primarily a varmint load, the 90-grain Sierra HPBT HPBT Hollow Point Boat Tail (bullet)  over 65.3 grains of H-4350 gave a sizzling 3,511 fps and would pretty much annihilate an·ni·hi·late  
v. an·ni·hi·lat·ed, an·ni·hi·lat·ing, an·ni·hi·lates
a. To destroy completely: The naval force was annihilated during the attack.
 any small critter within sight.

At least one standout hunting load was discovered with each of the heavier bullets. The 100-grain Nosier Partition over 69.5 grains of IMR 7828 turned in the smallest group average of all loads tested, at.74 inch. Not far behind was the 115-grain Ballistic Tip at.89 inch at 2,988 fps over 68 grains of RL-25. The 100-grain Barnes TS-X over 67 grains of H-4831 gave 3,225 fps. And the 100-grain Sierra GameKing, Speer Hot-Cor and Swift Scirocco sci·roc·co  
Variant of sirocco.
 II bullets did well.

The new 110-grain bonded bullets from Hornady and Nosier are a bit heavier and will hold together no matter what. Vihtavuori N-165 and IMR 7828 were the powder picks here.

It was a toss-up between the four great 120-grain bullets. The Speer Grand Slam grand slam
1. The winning of all the tricks during the play of one hand in bridge and other whist-derived card games.

2. Sports The winning of all the major or specified events, especially on a professional circuit.
 and Nosier Partition are perennial favorites of big-game hunters, as is the bonded-core Swift A-Frame. With near-maximum charges of H-1000, RL-25 and IMR 7828, groups were only a smidgen over an inch even.

If you need a cartridge to reach out and touch big game in the next zip code, the.257 Weatherby Magnum is an authentic original that is perfect for the job.




The loads shown here are safe only in the guns for which they were developed. Neither the author nor InterMedia Outdoors Inc. assumes any liability for accidents or injury resulting from the use or misuse of this data.
              WEIGHT                            (CR.)  VELOCITY
               (CR.)                                      (FPS)

BARNES TS-X      100  Wby.  Fed-215  H-4831      67.0     3,225

BARNES           115  Wby.  WLRM     H-4831      63.5     3,017

HORNADY          110  Wby.  Fed-215  VVN-165     65,0     3,042

HORNADY BTSP     117  Wby.  Fed-215  RL-25       67.0     2,994

NOSLER           100  Wby.  Fed-215  IMR-7828    69.5     3,180

NOSLER           110  Wby.  Fed-215  IMR-7828    69.5     3,202

NOSLER           115  Wby.  CCI-250  RL-25       68.0     2,988

NOSLER           120  Wby.  WLRM     MRP-2       72.0     3,075

SIERRA HPBT       90  Wby.  Fed-215  H-4350      65.3     3,511

SIERRA           100  Wby.  Fed-215  H-4350      61.0     3,287

SIERRA           117  Wby.  CCI-250  H-4831      64,7     3,028

SPEER            100  Wby.  Fed-215  Magnum      72.0     3,151

SPEER            120  Wby.  WLRM     H-1000      72.0     3,154

SPEER GRAND      120  Wby.  CGI-250  Re-25       67.0     2,971

SWIFT            100  Wby.  Fed-215  H-1000      76.0     3,479

SWIFT            120  Wby.  Fed-215  IMR7828     68.0     3,054

BULLET        STD.   AVG.    MUZZLE    COL
              DEV.  GROUP    ENERGY  (IN.)
                    (IN.)  (ft-lbs)

BARNES TS-X     24   1.28     2,310   3.20

BARNES          17   1.21     2,325   3.20

HORNADY         20   1.20     2,261   3.22

HORNADY BTSP    24   1.26     2,329   3.20

NOSLER          20   0.74     2,246   3.20

NOSLER          16   1.27     2,505   3.20

NOSLER           8   0.89     2,280   3.25

NOSLER           7   1.23     2,520   3.20

SIERRA HPBT     32   1.24     2,464   3.07

SIERRA          17   1.17     2,400   3.16

SIERRA          26   1.25     2,383   3.21

SPEER           44   1.26     2,205   3.16

SPEER           16   1.17     2,651   3.23

SPEER GRAND     14   1.16     2,353   3.20

SWIFT           29   1.30     2,688   3.25

SWIFT           24   1.19     2,486   3.20
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Title Annotation:G&A RELOADS
Author:Gash, Steve
Publication:Guns & Ammo
Date:Apr 19, 2012
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