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.340 Weatherby Magnum


When Winchester released the .338 Winchester Magnum in 1958, they established the .338” as a mainstream caliber which was supported by readily available ammunition and components.  With an accepting market, ensuring sustainability of component projectiles, Roy Weatherby created his own super charged proprietary .338” caliber cartridge.  Released in 1962, the 340 Weatherby Magnum was based quite simply on the .300 Weatherby cartridge necked up to .338 caliber. The parent .300 cartridge is in turn based on the full length .375 H&H case necked down to .338” with a double radius case shoulder. The resulting .340 Weatherby cartridge was very similar to the magnum wildcat .334 OKH favored by U.S gun writer Elmer Keith. 
The .340 gained a steady following for use on large North American and Alaskan game however its popularity remained somewhat limited due to the high level of recoil. Ironically, the .338 Lapua cartridge introduced much later became immensely popular and generated further interest in hot .338 magnums including the giant .338-378 Weatherby while the original .340 Weatherby continued to maintain a more modest following. One is almost reminded of the fable of the hare and the tortoise, although in this case the tortoise is not so modest, generating around 4830 ft-lb energy, a rather dangerous tortoise.
The .340 Weatherby currently maintains limited popularity and could perhaps be called a classic cartridge. Velocities are identical to the standard .338 Lapua loading consisting of a 250 grain bullet at 2950fps. The Weatherby cartridge utilizes a good deal of free bore which is possibly not of great necessity with this case to bore ratio but is provided all the same for maximum velocity generation. As a large game cartridge, the Weatherby has great merit and those how use it, tend to develop a great respect for its performance.



The power of the .340 can be utilized in two ways. On light to mid weight game, increased velocity in comparison to the smaller .338’s helps to ensure increased target resistance and therefore increased energy transfer. This results in fast killing out to greater distances. On large and heavy game, the .340 can drive very long for caliber bullets at high velocities, ensuring deep bone smashing penetration, thereby increasing the flexibility of the .338 bore which although designed for large game, was not intended as a heavy game bore diameter.
The trade off for this performance is increased recoil to both the shooter and rifle platform. Further to this, the traditional Weatherby rifles, while elegant, could never be classed as recoil taming designs. The unfortunate result of this is the occasional hunter wielding a hopelessly inaccurate rifle, living by the fantastical rule that this cartridge can deliver the goods, regardless of shot placement or rifle accuracy. The correct term for this is minute of ego.
Bedded and with a light and crisp trigger combined with practice and self-discipline, the .340 Weatherby can be coaxed to shoot well in its factory configuration. Nevertheless, a muzzle brake can help tame recoil a great deal and a brake is in some ways a necessity on such rifle designs. However, yet another trade off is made, recoil for noise- dangerous levels of noise. In this regard, rifle configuration and usage require a good deal of consideration.

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Factory ammunition

Initially, the published velocities for Weatherby (Norma) factory ammunition were somewhat optimistic. Current loads are more or less true to advertised speeds when utilized in 26” barreled rifles but can fall short by up to 70fps. Weatherby loads include the 200 grain Accubond at 3225fps, the 210 grain Partition at 3211fps, the 225 grain Hornady Interlock at 3066fps, the 225 grain Barnes TSX at 3000fps, the 250 grain Hornady Interlock at 2963fps and the 250 grain Nosler Partition at 2941fps. A major downside of Weatherby ammunition is the horrendous cost.
The 200 grain Accubond is a good general purpose bullet for larger bodied deer weighing between 90 and 320kg (200-700lb) out to ranges of around 450 yards. The Accubond is placed under a great deal of stress at close ranges which can limit its performance on heavier animals.
The 210 grain Nosler Partition was designed for use on Elk sized game and at .340 velocities, kills can be spectacular out to moderate ranges on mid to larger bodied deer. Maximum effective range for this load in rifles with suitable long range optics is around 675 yards however shot placement is critical at this range and can be difficult to achieve relative to wind drift. To this end, an effective range of around 450 yards can be more realistic.
The 225 grain Interlock is suitable for game up to 320kg as an open country load but is too soft for heavily raking shots. At close ranges, under 100 yards, this bullet is prone to blow up when striking major bones (sometimes on relatively light framed game). Generally speaking, in the .340, this bullet is best used on light to mid weight deer species. The Interlock produces vivid expansion at extended ranges and is much like the Partition load. By the same token, shot placement becomes ever more important as velocity falls away.
The 225 grain Barnes TSX produces fast kills on game in the 90 to 320kg out to 200 yards, with clean but sometimes delayed killing thereafter depending on shot placement. This bullet can be used on relatively heavy game and is the toughest Weatherby factory load.
Weatherby’s 250 grain Hornady Interlock load is suitable for game up to the size of Elk but on larger game is prone to bullet blow up when encountering heavy bone. For game weighing between 90 and 320kg (198 to 700lb), the 250 grain Interlock produces fast kills out to ranges of around 160 yards and clean killing out to ranges of around 370 yards.
The 250 grain Partition is a wonderful bullet for large North American game, This bullet produces fast killing on game in the 90 to 320kg (200-700lb) range out to around 180 yards and is a clean killer on all game up to 600kg (1300lb) out to moderate ranges. The Partition is not ideally suited to extremely heavy, tough game in the same manner as a heavy Woodleigh or Swift bullet but its performance is nevertheless outstanding.


Hand loading

Weatherby .340 brass is not overly common however cases can easily be formed by simply necking up .300 Weatherby cases. Norma (Weatherby) brass is recommended for this due to its generous internal case capacity and general uniformity.
The .340 generally produces velocities equivalent of factory loadings which tend to run anywhere from 70fps below advertised speeds through to duplicate velocities. The .340 produces extremely good results with slow burning powders in the H4831sc (ADI 2213sc)  range through to the slower H1000 (ADI 2217) burn rates which can prove optimal.  Comfortable velocities include 3450fps with the 160 grain Barnes, 3350fps with 180 grain bullets, 3250fps with 200 grain bullets, 3150fps with 210 grain bullets, 3050fps with 225 grain bullets, 2950fps with 250 grain bullets, 2850fps with the 275 grain Swift, 2700fps with the 285 grain A-Max / ELD and velocities of around 2600 to 2650fps with 300 grain bullets.
Free bore of the .340 is long, but the long neck of Weatherby case design can be used to ensure optimum bullet to bore alignment. The .340 requires a very long magazine and is best housed either on the Mk V rifle action or rifles featuring Wyatt extended magazine boxes.
In very high recoiling rifles, full velocities may simply produce poor accuracy which may be due to either shooter error or rifle limitations. To this end, hand loaders should set realistic expectations as to potential velocities based on individual circumstances.
Projectiles that are considered soft when loaded in the Winchester are more prone to blow up in .340. This can be both useful or a hindrance depending on how the .340 is used. The bulk of my .338 projectile research can be found in the .338 Winchester text which serves as the base reference article for this bore diameter. The ahead text will therefore explore a more limited range of useful .338” projectiles from economical conventional bullets through to premium designs.  These notes are also relevant to the .338 Lapua and .338 RUM which produce identical velocities.
For light framed game, few other .338 bullets can compare to the 200 grain SST. Performance at full .340 velocities is extremely violent. The SST is capable of full expansion down to velocities of around 1600fps offering obvious long range potential. Having said this, on lean game, rear lung shots can produce delayed killing at impact velocities below 2400fps. Internal wounding remains thorough below 2400fps so although killing is delayed, it can be called clean- much like that achieved with a hunting bow. To create fast killing at extended ranges, shots need to be placed into the shoulders of game as opposed to the meat saver type shot. 
The 225 grain Hornady SST and Interbond Bullets make for an extremely versatile dual loading.  The SST is suitable for game weighing as light as 40kg (88lb) at both close and longer ranges and is suitable for game up to 320kg (88-700lb) in open country hunting/ longer range situations. 
The tougher Interbond is more suitable for game weighing between 90 and 320kg (198-700lb) where raking but not tail on shots may be encountered. The SST produces a wide frontal area resulting in high shock along with large exit wounds, prone to bullet blow up on the lightest of game, producing spectacular kills. For game weighing between 90 and 320kg the SST should be annealed (see annealing article) to prevent bullet blow up. Nevertheless, weight retention of the annealed .338” SST can be less than 50% at .340 velocities.  The SST produces the most severe wounding of all .338 projectiles currently available, game hit with this bullet either go down immediately or do not travel far. From a muzzle velocity of 3050fps the SST produces fast killing on light through to Elk sized game out to 200 yards. Beyond 200 yards, frontal chest shots cause death within 5-10 yards but rear lung shots may produce no sign of a hit on lean game with animals able to travel 30-70 yards. Wounds are severe out to 300 yards and steadily taper off thereafter, remaining vivid down to impact velocities of 1600fps.  The 225 grain Interbond is ideally suited to game in the 90 to 320kg range and adequate for cross body shooting of game up to 450kg (1000lb). Results on lighter game are not as spectacular as the SST as the Interbond is not prone to bullet blow up.   For game the size of Red deer/ Caribou through to Elk the Interbond can be annealed to maximize penetration.  Performance of the Interbond is similar to other core bonded designs however the Interbond is extremely economical in comparison.
The 285 grain Hornady A-Max (now ELD-M) can be put to use in the .340 with a good deal of success. Sweet spots can be found at muzzle velocities of between 2600 and 2700fps. This velocity range is ample for the A-Max / ELD-M  which is effective down to 1400fps, making it an excellent long range hunting bullet. The A-Max can be used on very lean game through to large bodied deer and antelope with great success. This bullet should not be used on any potentially dangerous game due to its frangible nature.
The Nosler Partition range of bullets are extremely useful in the big .338’s. These offer a level of versatility with the front core of the bullets being very soft while the rear core remains intact under most circumstances. These bullets are available in the weights 210, 225 and 250 grains. The newer Accubond bullets also have merit but with limitations, being prone to excessive weight loss if used on heavy animals at close ranges and yet, should be considered stout if used at very long ranges. Mid weight game and normal hunting ranges are key factors when using the Accubond.
Speer have a very useful .338 bullet- the 225 grain BTSP, a soft bullet, ideal for extended range / low velocity killing. It sometimes seems as if Vernon Speer was decades ahead of his time in this regard. The Speer BTSP is yet another bullet well suited to larger bodied deer and can tackle relatively heavy body weights at extended ranges.
Sierra’s 250 grain Gameking is vastly different to the Speer BTSP. The jacket of the Sierra is much tougher, it’s SD higher. Both were designed for extended range shooting at a time when long range shooting consistent of cross valley shots out to around 400 yards or so. However, the Sierra was built relatively tough should closer range shots be encountered. The GameKing design works as intended once these design parameters are understood. By the same token, this is not a heavy game bullet due a lack of controlled expansion while at the time, its jacket can be too tough for truly long range shooting of mid weight deer species. Neither of these factors should be considered negatives, again in light of its design parameters.
The Rocky Mountain bullets can be used in the .340 Weatherby with great success. COAL’s are very long with bullet jump remaining equally long, but in rifles with suitable magazine lengths such as the Mk V, the Rocky Mountain bullets can be used out to ranges exceeding 1000 yards in expert hands. Performance of the Rocky Mountain bullets is simply exceptional.
For tough, heavy game, few projectiles can compare to the Woodleigh range. These projectiles are in essence the go to bullets if using the big .338’s on tough game weighing 450 kg (1000lb) and above, available in the weights 225 grains, 250 grains and 300 grains. The 300 grain round nosed Weldcore has obvious merit for the toughest situations and works best when driven fast with ranges kept short. This bullet is rated to an upper impact velocity of 2500fps however as is always the case with the high SD Woodleigh bullets, the 300 grain bullet simply shines at high impact velocities. Hunters should place shots into the forwards chest cavity of large bodied game, aiming to break major bones while also destroying vital tissues of the autonomic plexus. Woodleigh also produce a 300 grain FMJ bullet which has been used to take the heaviest game species in the world. The SD of this bullet weight is .375 and the case capacity of the Weatherby ensures that the 300 grain FMJ can be driven at good speeds.  
Swift produce several useful .338 projectiles including the 210 grain Scirocco and the A-Frame available in the weights 225, 250 and 275 grains. The Scirocco performs much like the Accubond and can be very useful for hunting larger bodied deer out to ranges of around 400 yards, steadily declining in performance but producing clean kills out to ranges of around 530 yards before performance begins to taper off in a more detrimental manner. The A-Frame bullets are, like the Woodleigh offerings, excellent performers where game weights exceed 450 kg (1000lb). Of the A-Frame bullets, the 275 grain projectile is a gem. Its weight is such that its SD and momentum are very high, while not being so heavy as to slow the bullet right down. This was a bullet weight that gun writer Elmer Keith very much favored for large bodied game and one cannot help but wonder if Keith’s comments were influential in its design. As Keith would have suggested, drive it fast and get in close. This combined with accurate shot placement ensure excellent results.


Closing comments

The .340 Weatherby is becoming somewhat rare these days but still maintains a loyal following. This is an extremely potent and effective cartridge and its velocity gains over the original Winchester cartridge can be exploited on both lighter framed game and tough heavy game. However; this increase in performance comes at the cost of recoil to both the rifle platform and shooter which can have a negative effect on accuracy.  If the .340 is expected to excel, the rifle must be accurate and the shooter comfortably confident enough to place projectiles where they will do the most damage. Following this, bullet weights and bullet designs need to be matched to the job at hand. The .338 bore can at times be unforgiving if these basic rules are not adhered to and without this attention to detail, this bore diameter is best used as it was initially intended, for hunting large but not heavy game. Success is entirely within the hands of the shooter.

Suggested loads: .340 Weatherby Magnum Barrel length: 26”
No ID   Sectional density Ballistic coefficient Observed  MV Fps ME
1 HL 200gr SST .250 .455 3200 4547
2 HL Hornady SF 225gr SST/IB .281 .515 3050 4647
3 HL 250gr Rocky Mountain .281 .846 2950 4830
4 HL 300gr Woodleigh RN .416 .332 2650 4677
Suggested sight settings and bullet paths         
1 Yards 100 175 298 339 350 375 400
  Bt. path +3 +4 0 -3 -4 -6.4 -9.2
2 Yards 100 150 283 325 350 375 400
  Bt. path +3 +3.7 0 -3 -5.4 -8.1 -11.1
3 Yards 100 150 283 325 350 375 400
  Bt. path +3 +3.7 0 -3 -5.2 -7.7 -10.5
4 Yards 50 100 200 232 250 275 300
  Bt. path +.9 +2 0 -2 -3.5 -5.8 -8.7
No At yards 10mphXwind Velocity Ft-lb’s
1 300 5.7 2575 2945
2 300 5.3 2512 3151
3 300 3.3 2622 3815
4 100 .8 2439 3962
340 weatherby final
.340 Weatherby Imperial Metric 
A .532 13.51
B .512 13
C R.151  
D .492 12.5
E .365 9.27
F 2.298 58.36
G .340 8.6
H 2.825 71.76
Max Case 2.825 71.76
Trim length 2.815 71.46
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We are a small, family run business, based out of Taranaki, New Zealand, who specialize in cartridge research and testing, and rifle accurizing.