.338 Norma Magnum

The .338 Norma Magnum began as a wildcat cartridge built by the American competitive shooter Jimmy Sloan, with reamers and gauges from Dave Kiff of Pacific Tool and Gauge and barrels from Rock Creek Barrels. Sloan built it specifically around the 300-grain Sierra MatchKing bullet, a projectile not yet available when the earlier .338 Lapua Magnum was designed, which is why that cartridge’s own factory loadings favour lighter 250- to 285-grain bullets instead. Sloan’s aim was to seat that heavier bullet efficiently in actions and magazines too short for the .338 Lapua Magnum’s full overall length. Norma, the Swedish ammunition maker, later bought the design, and C.I.P. certified it on 26 May 2010.

To fit the same 300-grain bullet into a shorter overall cartridge, Norma’s case is shorter than the Lapua Magnum’s, with less body taper, a sharper shoulder and a longer neck, giving it roughly six and a half percent less internal case volume. That smaller case gives up some muzzle velocity compared to the Lapua Magnum, a deficit its makers argue is offset by the better ballistic efficiency of the heavier bullet it was built around, though the two cartridges’ practical difference narrows once a rifle’s magazine is long enough to load the Lapua Magnum to its own full length.

A 2008 U.S. government market survey for a new precision sniper rifle specified a chambering for factory, non-wildcat .338-calibre ammunition, a requirement the Norma round was positioned to fill alongside the Lapua Magnum. In 2019 the U.S. Special Operations Command selected the Barrett MRAD, designated the Mk 22 Advanced Sniper Rifle, in a chambering package that includes .338 Norma Magnum alongside 7.62×51mm NATO and .300 Norma Magnum, and in 2020 SIG Sauer’s MG 338 machine gun was ordered in the same chambering. This is one of relatively few instances of a cartridge built for a bolt-action sniper rifle being adopted for a belt-fed gun as well.

Every dimensional figure on this page comes from C.I.P.’s own published standard and is recorded as verified. The bullet mass and velocity recorded here come from Black Hills Ammunition’s own current product listing rather than Wikipedia’s uncited infobox figure, which gives a very similar but not identical velocity for the same bullet weight. This is a reminder that different manufacturers’ loads of the same nominal bullet weight are not interchangeable figures.