.338 Winchester Magnum (using Sierra bullets)
Date: May 24 2016
Winchester announced the .264 and .338 Winchester Magnums in 1958, which were “short magnums” for their era, as they were designed to function in .30-06-length actions rather than the longer .300 and .375 H&H Magnum action lengths. The .338 filled the gap between the .30-caliber magnums and .375 H&H Magnum, and it has proven to be an outstanding large game cartridge with versatility. It is widely popular in Alaska among hunters and guides in pursuit of brown bear and moose and is also popular in Africa for heavy plains game. It offers a blend of flat trajectory and medium-bore punch with comparatively manageable recoil.
In developing handload data, the cartridge delivered outstanding shot-to-shot consistency and accuracy without erratic pressure curves. In spite of many new .338-caliber cartridge developments in the decades since its introduction. The .338 Winchester Magnum remains the most popular among hunters around the world.
If ammunition is to be used in multiple rifles, cases should be full-length sized to assure they will chamber easily in all guns. If loading for a single rifle, to increase case life, size cases so that they headspace on the shoulder rather than the belt.
When using the Sierra 300-grain HPBT MatchKing bullets, they were seated to an overall cartridge length of 3.410 inches, which exceeds the industry maximum overall cartridge length of 3.340 inches. Many magazine rifles will not accept a cartridge of this length, and cartridges may need to be chambered in single-shot mode. A Ruger M77 MKII test rifle fed and functioned reliably with cartridges of this dimension.
To achieve reliable ignition with all powders and in a variety of temperatures, large rifle magnum primers are suggested, with the Federal 215 primers used herein.