Home › Browse Calibers › .338-378 Wby. Mag.
Common uses: Hunting, Big Game, Long Range
| Type | rifle (centerfire) |
| Typical load | 250gr Weatherby Select Nosler Partition |
| Muzzle velocity | 3060 fps |
| Muzzle energy | 5199 ft-lb |
| Stored G1 ballistic coefficient | 0.473 |
| Case length | 73.99 mm |
| Overall length | 3.75 in |
| Listed maximum pressure | 65000 PSI |
| Range (yd) | Velocity (fps) | Energy (ft-lb) | Drop (in) |
|---|---|---|---|
| 0 | 3060 | 5197 | -1.5 |
| 100 | 2853 | 4516 | 0 |
| 200 | 2656 | 3914 | -2.8 |
| 300 | 2467 | 3379 | -10.5 |
| 400 | 2286 | 2901 | -24 |
| 500 | 2113 | 2478 | -44.1 |
At 1,000 yards, .338-378 Wby. Mag. (250gr at 3060 fps, 100 yd zero, standard conditions) has a modeled come-up of about 28.1 MOA / 8.2 MIL, retaining 1381 fps (supersonic).
| Range (yd) | Velocity (fps) | State | Drop (in) | Elev (MOA) | Elev (MIL) |
|---|---|---|---|---|---|
| 300 | 2468 | Supersonic | -10.5 | 3.3 | 0.97 |
| 400 | 2287 | Supersonic | -23.9 | 5.7 | 1.66 |
| 500 | 2114 | Supersonic | -44.0 | 8.4 | 2.44 |
| 600 | 1948 | Supersonic | -71.9 | 11.4 | 3.33 |
| 700 | 1791 | Supersonic | -109.0 | 14.9 | 4.32 |
| 800 | 1643 | Supersonic | -156.9 | 18.7 | 5.45 |
| 900 | 1506 | Supersonic | -217.8 | 23.1 | 6.72 |
| 1000 | 1381 | Supersonic | -294.0 | 28.1 | 8.17 |
Extended predictions beyond 500 yards are modeled from the same G1 engine — useful for initial DOPE, but outside the 500-yard manufacturer-table validation audit. Confirm with observed DOPE, especially near transonic.
A retained-energy reference only — not a shoot/don't-shoot distance. Real effective range depends on your accuracy, shot placement, bullet construction, and conditions. The ~1,000 ft-lb (deer-sized) and ~1,500 ft-lb (elk-sized) figures are commonly cited rules of thumb, not standards.
Published BCs depend on a reference drag model and stated velocity conditions. A source review does not independently measure a BC. Understanding BC sources
Your barrel, ammunition lot, and conditions will differ — always verify against the manufacturer's data and your own rifle.
This is an overbore, high-velocity magnum built to drive heavy .338 bullets flatter and faster than nearly any other cartridge in its class, making it a specialist choice for long-range shots on large, heavy game. It is favored for open-country hunting of elk, moose, big bears, and African plains game, where its retained energy and flat trajectory extend a shooter's reach considerably. Those gains come at a steep price: severe recoil, a large powder charge that burns barrels comparatively quickly, and the bulk and expense of a full-length Weatherby magnum action and ammunition. It rewards experienced shooters who can manage its punishing recoil but offers little advantage for ordinary hunting distances where lesser cartridges suffice. In practice it occupies a niche among those who genuinely need extreme downrange performance and are willing to accept the trade-offs to get it.
The .338-378 Weatherby Magnum traces to a 1966 wildcat, the .338-378 KT, developed by Elmer Keith and R.W. "Bob" Thomson by necking the .378 Weatherby Magnum case down to .338 caliber. Weatherby standardized and commercialized the round in 1998, using the full-length belted .378 Weatherby parent case. The design goal was maximum velocity from a .338-bore bullet, and it remains one of the fastest factory .338 cartridges available.
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