The .300 WSM
By Chuck Hawks
The .300 WSM (Winchester Short Magnum) is the most popular and widely distributed of the modern crop of short magnum cartridges in terms of both factory loaded ammunition and rifles available. It has slightly less powder capacity than the standard length .300 Winchester Magnum. With bullets in the 150-180 grain weight range, however, its performance is essentially identical to that of the established .300 Win. Mag.
Winchester figures for the .300 WSM with a 24" test barrel claim a muzzle velocity of 3300 fps and ME of 3628 ft. lbs. for the 150 grain bullet. The 200 yard figures are 2834 fps and 2676 ft. lbs.
Winchester claims a MV of 2970 fps with 3526 ft. lbs. of muzzle energy for the 180 grain bullet. The 200 yard figures are 2524 fps and 2547 ft. lbs. Those figures are nearly identical to the velocity of the .300 Winchester Magnum taken in the same length barrel, and also to the figures for the .300 Rem. SAUM in a 24" test barrel.
Here are some .300 WSM statistics of interest to reloaders: bullet diameter .308", maximum COL 2.86", maximum case length 2.10".
Like all .30 caliber cartridges, there is a huge array of bullets available to the .300 WSM reloader, ranging from 100-250 grains. However, the very light 100-125 grain bullets make little sense in any .300 Magnum cartridge, and the short .300 WSM case does not handle bullets heavier than 180 grain very efficiently. So bullets from 150-180 grains are usually the best choice in the .300 WSM.
The medium to slow burning rifle powders work best in the .300 WSM. Examples include H380, H414, H4831, IMR 4064, IMR 4350, IMR 4831, VIHT N-550, and W760.
The fifth edition of the Nosler Reloading Guide shows that 56.5 grains of IMR 4064 behind their 150-155 grain bullets produced a MV of 3063 fps. A maximum load of 60.5 grains of the same powder produced a MV of 3242 fps. IMR 4064 proved to be the most accurate powder with bullets of this weight in the Nosler tests.
Nosler figures show that 60.0 grains of H380 powder behind their 165-168 grain bullets gave a MV of 2940 fps, and a maximum charge of 64.0 grains of H380 gave a MV of 3087 fps. H380 was the most accurate powder with these bullet weights.
Nosler figures for the .300 WSM show that 61.0 grains of IMR 4350 powder will drive their 180 grain bullets to a MV of 2861 fps, and 65.0 grains of the same powder will give a MV of 3024 fps. Nosler used Winchester brass and primers for these loads. All of these Nosler loads used Winchester brass and WLRM primers. Note that these Nosler figures were developed in a 26" test barrel.
Note: A full length article about the .300 WSM can be found on the Rifle Cartridges page.
Copyright 2004, 2016 by Chuck Hawks. All rights reserved.