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338 Lapua Magnum was last updated: 20100126 2309

338 Lapua Magnum
The .338 Lapua Magnum (8.6x70mm or 8.58x70mm) is a specialized rimless bottlenecked centerfire cartridge developed for military long-range sniper rifles. The Afghanistan War and Iraq War made it a combat-proven round with ready and substantial ammunition availability. The .338 Lapua is a dual-purpose anti-personnel and anti-materiel round; however, its anti-materiel potential is limited, due to the bullet's lower kinetic energy compared with that of the .50 BMG's 35.64 to 55.08 gram (550 to 850 grain) projectiles. The loaded cartridge is 14.93 mm (0.5878 in) in diameter (rim) and 93.5 mm long. It can penetrate better-than-standard military body armour at ranges up to 1,000 metres (1,094 yd) and has a maximum effective range of about 1,750 metres (1,910 yd). Muzzle velocity is dependent on load and powder temperature and varies from 880 to 915 m/s (2,900 to 3,000 ft/s) for commercial loads with 16.2 gram (250 grain) bullets, which results in about 6525 joules (4813 ft·lbf) of muzzle energy.

In addition to its military role, it is increasingly used by hunters and civilian long-range shooting enthusiasts. The .338 Lapua Magnum is capable of taking down any game animal, though its suitability for some dangerous game (Cape buffalo, hippopotamus, white rhinoceros and elephant) is arguable, unless accompanied by a larger "backup" caliber: "There is a huge difference between calibers that will kill an elephant and those that can be relied upon to stop one."[4] Certain sub-Saharan Africa countries have a 9.53 mm (.375 in) minimum caliber rule for hunting the Big Five. It also cannot be used in countries which ban civil use of former or current military rifle cartridges.

In 1983, Research Armament Industries (RAI) in the USA began development of a new, long-range sniper cartridge capable of firing a 16.2-gram (250 gr), 0.338-inch (8.6 mm) diameter bullet at 914 metres per second (3,000 ft/s) that could penetrate 5 layers of military body armor at 1,000 m (1,094 yd) and still make the kill. After preliminary experiments, a .416 Rigby case necked down to take a 0.338-inch (8.6 mm) bullet was selected, since this diameter presents an optimum of sectional density and penetrating capability for practical spin stabilized rifle bullets (bullets up to about 5 to 5.5 calibers in length).[5] The .416 Rigby is an English big game cartridge that was designed to accommodate 325 MPa (47,137 psi) pressures. One of the disadvantages of these old cartridge cases, which were intended for firing cordite charges instead of modern smokeless powder, is the thickness of the sidewall just forward of the web. During ignition, the cartridge's base, forward to the bolt face, is not supported. The case is driven back against the bolt face which results in the stretching of the case, particularly the sidewall immediately forward of the web. When the sidewall resists the outward expansion against the chamber, the pressure stretches the case thereby increasing its length resulting in the sidewall becoming thinner at that stretch point.

During the process RAI employed Brass Extrusion Labs Ltd. (BELL) of Bensenville, Illinois, to make the .338/416 or 8.58x71mm cartridge cases, Hornady produced bullets, and RAI built a sniper rifle under contract for the U.S. Navy. RAI found that the BELL cases did not fulfill the requirements. Pressed by military deadlines RAI looked for another case producer and got into contact with Lapua of Finland[6] in 1984. Due to financial difficulties RAI was forced to drop out of the program. Subsequently, Lapua of Finland put this (wildcat) cartridge into limited production.[7] The .338/416 rifle program was later cancelled when the contractors were unable to make the cartridge meet the project's velocity target 16.2 gram at 914 m/s (250 gr at 3000 ft/s), due to weak brass cases.

From its American origins, the current .338 Lapua Magnum cartridge was developed as a joint venture between the rifle building company Accuracy International and the Finnish ammunition manufacturer Lapua (including personal communication with Malcolm Cooper, the now-deceased founder of Accuracy International). In some contrast to this, Lapua states on its website that it developed the cartridge and mentions Mr. Cooper's Accuracy International as a cooperation partner.[8] Since Mr. Cooper cannot comment on this matter it cannot be resolved.

Lapua opted to elaborately redesign the .338/416 cartridge. In the new case design, particular attention was directed toward thickening and metallurgically strengthening the case's web and sidewall immediately forward of the web. In modern solid head cases, the hardness of the brass is the major factor that determines a case's pressure limit before undergoing plastic deformation. Lapua tackled this problem by creating a hardness distribution ranging from the head and web (hard) to the mouth (soft) as well as a strengthened (thicker) case web and sidewall immediately forward of the web. This resulted in a very pressure resistant case, allowing it to operate at high pressure and come within 15 m/s (50 ft/s) of the original velocity goal. Lapua also designed a 16.2-gram (250 gr) .338 calibre Lock Base B408 full metal jacket bullet, modeled after its .30 calibre Lock Base bullet configuration. The result was the .338 Lapua Magnum cartridge which was registered with C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) in 1989. With the procurement by the Dutch Army, the cartridge became NATO codified.

The .338 Lapua Magnum is considered an ideal military long-range anti-personnel cartridge by long-range sniping specialists like John D. Taylor and Dean Michaelis. It fills the gap between weapons chambered for standard military rounds such as the 7.62x51mm NATO and large, weighty rifles firing the .50 BMG cartridge. It also offers a tolerable amount of barrel wear, which is important to military snipers who tend to fire thousands of rounds in practice every year to acquire and maintain expert long-range marksmanship.[9] Like every other big cartridge the .338 Lapua Magnum presents a stout recoil. An appropriate fitting stock and an effective muzzle brake will help to reduce recoil induced problems, enabling the operator to fire more rounds before getting too uncomfortable to shoot accurately anymore. Good factory loads, multiple projectile weights and factory special application ammunition are all available.[10][11]

Due to its growing civilian popularity, several high quality tactical and match (semi) custom bolt actions designed for the .338 Lapua Magnum are becoming available. These (semi) custom bolt actions are used with other high grade rifle and sighting components to build custom sporting and target rifles.