30-378 Weatherby

Historical Notes:

This cartridge was developed specifically for use in 1000 yard benchrest competition. It was created by simply necking the 378 Weatherby case to accept 30 caliber bullets. The standard design retains the trademark Weatherby double radius shoulder.

General Comments:

The 30-378 case can hold over 120 grains of powder, compared to about 90 grains of the 300 Weatherby. With the advent of new slower burning powders, increased capacity promises a useful advantage to the handloader (Recent availability of match grade bullets weighing 250 grains served to increase potential benefit, and resultant demand, for a chambering with increased powder capacity). The 30-378 Weatherby certainly delivers on this promise: It is a simple matter to load 250 grain Sierra Match King bullets to produce almost 3000 fps muzzle velocity without exceeding 30-06 pressure levels and that from a 26 inch barrel! Lighter bullets can be driven faster but with those this chambering offers less advantage over standard 300 Magnum chamberings. When bullets lighter than 200 grains are fired from a 26 inch barrel, this cartridge is only marginally superior to the 300 Weatherby. However, with 30 inch barrels installed, ballistic difference is significant with all bullet weights. Those looking for the ultimate long range hunting rifle for smaller species might give this rifle a hard look. A single shot rifle equipped with a 30 inch tube offers reasonable handling ease and, if chambered for this cartridge, would deliver huge doses of energy to a distant target with the flattest trajectory available. Accurate Arms data shows the 250 grain MK generating the same muzzle energy as the 458 Winchester Magnum when loaded to about the same pressure! How about a 300 grain VLD launched from a 30 inch barrel at 2800 fps?

Source: Cartridges of the World

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