The History of the 300 Lapua Magnum (from www.lapua.com)
Since its introduction, the .338 Lapua Magnum has been used as the parent case for a series of cartridges, in a number of different bore sizes. Some of these are similar to other existing wildcats, which are described here as well. The .300 Lapua Magnum was developed concurrently with the .338 Lapua Magnum, but didn’t receive the public notoriety of its more famous stable mate. In fact, few shooters were aware of this cartridge until it appeared in the Lapua and Vihtavuori Reloading Manuals in the 1990s. Both the .300 and .338 Lapua Magnums were formally approved by CIP in 1989. During its development, the round was originally called the .30 Lapua Magnum. It wasn’t until it was finalized that it became known as the .300 Lapua Magnum. The .300 Lapua Magnum is a purely Finnish design, the brainchild of Juha Evasoja. Juha was Lapua’s head engineer from the 1970s into the early 2000’s.
The .300 Lapua can be considered a spin-off of the original development process of the .338 Lapua Magnum. It remains a true wildcat, as no factory rifles have been chambered for it, nor has ammunition ever been commercially loaded. Lapua produced a single test lot of .300 Lapua Magnum cases bearing that headstamp, but it has not been produced since. Cases used in the existing rifles chambered for the .300 Lapua Magnum are normally formed from .338 Lapua Magnum brass, necked down to accept a .30 caliber bullet. The basic idea behind the .300 Lapua Magnum was to create a high velocity, flat-shooting .30 caliber cartridge, based on the existing .338 Lapua Magnum case. The .300 Lapua Magnum shares the same basic case dimensions as the .338 Lapua Magnum, differing mainly in the neck and shoulder areas. Case volume remains the same as the parent .338 Lapua Magnum. The .300 Lapua Magnum is one of the first .30 caliber Magnums to reach the magical 1000/mps (3300 fps) threshold with heavy weight bullets. Actually, the new Lapua development was the first of the .30 caliber “super magnums”, when the .300 Weatherby Magnum was generally considered to be the upper limit where .30 caliber rounds were concerned. The 30-378 Weatherby (based on the necked down 378 Wby Mag case), was still an experimental wildcat cartridge and not yet fully standardized by SAAMI or CIP. It was originally proposed that the hypothetical .300 Lapua Magnum military sniper round be loaded with a 12.6 g (194 grain) B406 FMJBT. Early research indicated that this combination would deliver a muzzle velocity of 1000/mps (3300 fps) from a 27 inch barrel.
The .300 Lapua Magnum has not become a production item, yet it still exists as a long-range target cartridge. It has a loyal following for this demanding game, which is not at all surprising. Delivering ballistic performance similar to the 30-378, it does not display the sensitivity to load variations common to the Weatherby. Being a standardized CIP cartridge, several gunsmiths have built long-range rifles around this impressive round. The .300 Lapua Magnum is at its best with very slow burning powders like Vihtavuori N170 or 24N41. Like other very large magnum cases, the .300 Lapua needs a Magnum primer for reliable ignition. No factory made rifles for the .300 Lapua Magnum have ever existed, but several gunsmiths have built rifles for this caliber. The main application of the .300 Lapua Magnum is long range target shooting.