.300 Winchester Short Magnum
Date: Apr 15 2020
The .300 Winchester Short Magnum was introduced in 2001 as a joint effort between Winchester Ammunition and Browning/USRAC, and has become the most successful commercially available short .30-caliber Magnum cartridge. The short magnum concept was not a new idea, as wildcatters developed similar cartridges even before World War II, and there was renewed interest in similar wildcats in the decade previous to the .300 WSM’s introduction.
With trends toward lighter field rifles, the .300 WSM could be housed in a .308 Winchester length action, which reduced weight and overall length, and with 150- to 180-grain bullets it nearly duplicates .300 Winchester Magnum ballistics while using less powder. It is suitable for all North American game and African plains game with correct bullet choices. Most major U.S. rifle manufacturers have or still offer it, while Winchester, Remington, Federal and others produce a variety of loads. In spite of its many virtues, it has not supplanted the widely popular .300 Winchester Magnum.
In developing the accompanying data, low extreme velocity spreads were often recorded by the chronograph, which in many instances ranged from 8 to 20 fps for a 5-shot string.
Maximum listed loads should be approached with caution, as the pressure curve seems to increase rather quickly as charges approach maximum, and some rifles will show higher pressures sooner than others. Most ball (or spherical) powders can produce erratic pressures and even hangfires if the charge is below 80 percent to 85 percent of case capacity. Therefore suggested “start” powder charges should not be reduced. Examples include Winchester 760, Hodgdon H-414, Accurate Magpro and Ramshot Big Game. Each of these powders proved excellent choices when charges were at, or near maximum.
Extruded powders likewise gave excellent performance, yielding accuracy and top-notch velocities. Examples included Accurate AAC-4350, IMR-4350, IMR-4831, Hodgdon H-4350 and Alliant RL19.