| .338-378 Weatherby Magnum | |
| Origin: | United States |
| Type: | Centerfire/Rifle |
| Designer: | Elmer Keith and Bob Thomson |
| Design Date: | 1963 |
| Manufacturer: | Weatherby |
| Production Date: | 1998 |
| Parent: | .378 Weatherby Magnum |
| Case Type: | Belted, bottleneck |
| Bullet: | .338 |
| Neck: | .361 |
| Shoulder: | .560 |
| Base: | .582 |
| Rim Dia: | .579 |
| Rim Thick: | .059 |
| Case Length: | 2.905 |
| Length: | 3.65 |
| Case Capacity: | 125 |
| Rifling: | 1 in 10 |
| Primer: | Magnum Rifle |
| Max Pressure: | 63817 |
| Bw1: | 250 |
| Btype1: | Partition type |
| Vel1: | 3060 |
| En1: | 5197 |
| Bw2: | 225 |
| Btype2: | Truncated solid |
| Vel2: | 3180 |
| En2: | 5052 |
| Bw3: | 200 |
| Btype3: | Boat-tail soft point |
| Vel3: | 3350 |
| En3: | 4983 |
| Test Barrel Length: | 28 in (71 cm) |
| Balsrc: | Weatherby [1] |
The .338-378 Weatherby Magnum is based on the .338-378 KT, a wildcat cartridge created by Elmer Keith and R.W. "Bob" Thomson in 1966.[2] The KT is based on the .378 Weatherby Magnum cartridge but is shorter by 1/4" and necked down to a .338 caliber bullet.[3] This design was chosen for elk hunting, using the powders available at the time, such as Hodgdon H-4831.[4] Due to the continued popularity of the KT, Weatherby introduced the .338-378 Weatherby Magnum in 1998 to its line of commercial ammunition, using a full-length 2.908" case.[5] Although based on the .338-378 KT, the .338-378 Weatherby Magnum and the KT have different load data and chamber sizes and are not interchangeable.[6]
https://loaddata.com/Article/LabNotes/338-378-Weatherby-Magnum/621