The .300 Weatherby Magnum

By Chuck Hawks

.300 Wby. Mag.
Illustration courtesy of Hornady Mfg. Co.

So, you want a .300 Magnum? Well, here it is, the .300 that defines ".300 Magnum."

The .300 Weatherby is based on the full length .300 H&H case, blown out and given the Weatherby double radius shoulder. Heavy bullets do not have to be seated deep into the .300 Weatherby Magnum case as they do with the short magnum cartridges, or even the standard length .300 Win. Mag. The flip side of this is that a long magnum length rifle action is required for the .300 Weatherby.

The 2004 Weatherby catalog lists factory loads for several bullet weights, including 150 grain Hornady Interlock and Nosler Partition bullets at a claimed MV of 3540 fps. Weatherby offers 165 grain Hornady Interlock and Nosler Ballistic Tip bullets at a MV's of 3390 fps and 3350 fps respectively. Unlike the lesser .300 Magnums, the .300 Wby. is a true ultra-long range caliber when used with bullets of 150-165 grains.

The popular 180 grain weight is represented by Hornady Interlock, Nosler Ballistic Tip, Barnes X, and Nosler Partition bullets at MV's ranging from 3190-3250 fps. Heavy bullets are represented by the 200 grain Nosler Partition at a MV of 3060 fps and the 220 grain Hornady RN Interlock at a MV of 2845 fps.

As with most Weatherby calibers, medium-slow to slow burning rifle powders generally work best in the .300. IMR 4350, IMR 4831, H4350, H4831, VIHT N-165 and RL-22 are all good choices for bullets in the 150-180 grain range.

Here are some specifications of interest to reloaders: bullet diameter .308", maximum COL 3.560", maximum case length 2.825", MAP 65,000 psi.

The sixth edition of the Hornady Handbook of Cartridge Reloading shows that with their 150 grain bullets 69.0 grains of IMR 4831 powder gives a MV of 3000 fps. A maximum load of 81.0 grains of IMR 4831 gives a MV of 3500 fps.

The Hornady Handbook shows that with their 165 grain bullets 72.4 grains of RL-22 gave a MV of 2800 fps, while a maximum load of 84.0 grains of RL-22 gave a MV of 3300 fps. These Hornady loads were developed in Hornady cases using Federal 215 primers, and were tested in a 26" Weatherby rifle barrel.

Note: A full length article about the .300 Wby. Mag. can be found on the Rifle Cartridge Page.

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Copyright 2005 by Chuck Hawks. All rights reserved.