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 1000 meters (1094 yd) and has a maximum effective range of about 1750 meters. Muzzle velocity is dependent on load and powder temperature and varies from 880 to 915 m/s (2887 to 3002 ft/s) for commercial loads with 16.2 gram (250 grain) bullets, which results in about 6525 Joule (4813 ft•lbf) of muzzle energy.
In addition to its military role, it is increasingly used by big-game hunters and civilian long-range shooting enthusiasts. The .338 Lapua Magnum is suitable for hunting any game animal on the planet, though certain sub-Saharan Africa countries have a 9.53 mm (.375 in) minimum caliber rule for hunting Big Five game. It also cannot be used in countries which ban civil use of former or current military rifle cartridges.
In 1983, Research Armament Co. in the USA began development of a new, long-range sniper cartridge capable of firing a 16.2 gram (250 gr), .338-inch diameter bullet at 914 m/s (3000 ft/s) that could penetrate 5 layers of military body armor at 1000 m (1094 yd) and still make the kill. After preliminary experiments, a .416 Rigby case necked down to take a .338-inch 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). The .416 Rigby is an English big game cartridge that was designed to accommodate 325 MPa (47137 psi) pressures. One of the disadvantages of these old cartridge cases 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.
Brass Extrusion Labs Ltd. (B.E.L.L.) of Bensenville, Illinois, made the cases, Hornady produced bullets, and Research Armament built the rifle under contract for the U.S. Navy. Subsequently, Lapua of Finland put this calibre into production. The program was later canceled when they were unable to make it 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 American origins, the current .338 Lapua Magnum cartridge was developed as a joint venture between the rifle building company Accuracy International and 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. Since Mr. Cooper can not comment on this matter it can not be resolved. In the .338 Lapua Magnum cartridge 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, modelled 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. 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 the 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.
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. Such rifles are ordered by long-range, accuracy oriented shooters and are built by specialized, highly skilled gunsmiths. They can cost thousands of euros or dollars. When built to expectation, such rifles are very accurate - 0.5 MOA or better consistent accuracy for a particular rifle with optimized ammunition is considered normal. A large degree of skill is required to achieve this level of accuracy.
The Accuracy International AWSM rifle chambered in .338 Lapua Magnum is currently (2007) in service with the British Army and Royal Marines in Afghanistan and Iraq.
The .338 Lapua Magnum has been designated a "cartridge of interest" by the National Defense Industrial Association (NDIA). It is being groomed to replace the .300 Winchester Magnum and the .50 BMG for anti-personnel long-range service in the US Military.
Cartridge dimensions Edit
Extremely thick-walled brass results in a 7.40 ml (114 grains) H2O cartridge case capacity for the .338 Lapua Magnum. The exterior shape of the case was designed to promote reliable feeding and extraction in bolt action rifles and machine guns alike, under extreme conditions.
.338 Lapua Magnum maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).
Americans would define the shoulder angle at alpha/2 ≈ 20 degrees. The common rifling twist rate for this cartridge is 254 mm (1 in 10 in), 6 grooves, Ø lands = 8.38 mm, Ø grooves = 8.58 mm, land width = 2.79 mm and the primer type is large rifle magnum.
According to the official C.I.P. decisions and tables edition 2007 the .338 Lapua Magnum case can handle up to 420 MPa (60,916 psi) piezo pressure. This now prevails over the C.I.P. decisions and tables edition 2003, that rated the .338 Lapua Magnum at 470 MPa (68,167 psi) maximum piezo pressure. Remarkably the 470 MPa (68,167 psi) maximum piezo pressure C.I.P. ruling for the .300 Lapua Magnum cartridge, which is based on the same case, was not accordingly changed. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of the prevailing maximum C.I.P. pressure to certify for sale to consumers.
Lapua is ambivalent on the maximum piezo pressure of this cartridge. In the From an American dream to a Finnish success story article by Janne Pohjoispää Lapua propagates the C.I.P. 2006 ruling of 420 MPa (60,915 psi) maximum piezo pressure. To further complicate matters the mentioned 56,000 CUP C.I.P. copper crusher pressure in this article would translate in ≈ 447.5 MPa (64,903 psi) C.I.P. piezo pressure according to a study on the conversion from cup to psi for rifle cartridges by Denton Bramwell. The C.I.P. 2003 ruling of 470 MPa (68,167 psi) piezo pressure is corroborated by Lapua Australia in the History and development of the .338 Lapua Magnum article by Alan C. Paulson. A reverse engineering simulation with QuickLOAD internal ballistic software predicted that Lapua load their factory .338 Lapua Magnum ammunition at ≈ 420 MPa (60,915 psi) piezo pressure as Alan C. Paulson asserts in his article.
The large boltface combined with the high maximum pressure makes that the .338 Lapua Magnum should only be chambered in rifles that are capable of handling such large and fierce cartridges and thus high bolt thrust safely. Chambering such powerful super magnum cartridges in rifles intended for normal magnum rifle cartridges and using high pressure loads can cause serious or fatal injury to the shooter and bystanders.
The American .338-378 Weatherby Magnum cartridge introduced in 1998 and the American .338 Remington Ultra Magnum (.338 RUM) cartridge introduced in 2000 are probably the closest currently (2007) commercially available ballistic twins of the .338 Lapua Magnum. The .338-378 Weatherby Magnum is however a belted cartridge and the .338 Remington Ultra Magnum is a rebated rim cartridge.
Ballistic performance of the .338 Lapua Magnum Edit
For a typical .338 Lapua Magnum high end factory military sniper rifle like the Sako TRG-42 with a 690 mm (27.17 in) long 1 in 12 inch rifling twist rate barrel at sea level, 1500 m (1647 yd) is considered to be the maximum shooting distance for man sized targets when using standard Lapua military loads. The 16.2 gram (250 gr) Lapua Scenar GB488 bullet (G1 BC = 0.675), for which the Sako TRG-42 with its 1 in 12 inch twist rate was optimized, has a supersonic range of 1500 m under warm summer conditions at a muzzle velocity of 915 m/s (3002 ft/s). However, to be able to maintain over 90% hit probability on non-moving targets, this maximum shooting distance has to be reduced to 1300 m (1422 yd) at freezing point conditions or 1100 m (1312 yd) in Arctic winter conditions, when the muzzle velocity may drop to 880 m/s (2887 ft/s). Only during optimal warm summer conditions (muzzle velocity increases up to 915 m/s (3002 ft/s)) the maximum shooting distance of 1500 m (1647 yd) is realistically achievable.
Loaded with more aerodynamic .338 calibre bullets than the ones Lapua uses such as the Sierra HPBT Match King .338 19.44 gram (300 gr) bullet (G1 BC ≈ 0.768) or the Lost River Ballistics J40 .338 17.5 gram (270 gr) CNC manufactured mono-metal bullet (G1 BC = 0.871) the long-range performance and maximum range of .338 Lapua Magnum rifles can be extended. These longer very-low-drag bullets require a 1 in 10 inch twist rate to stabilize them. The .338 17.5 gram Lost River Ballistic Technologies J40 match bullet (G1 BC = 0.871) is one of the most aerodynamic .338 calibre bullets available. It has a 1829 m (2000 yd) supersonic range under optimal warm summer conditions at a muzzle velocity of 869 m/s (2850 ft/s). This makes engaging static targets up to 1800 m (1969 yd) feasible.
Improvement beyond this standard while still using standard .338 Lapua Magnum brass is possible, but the bullets have to be very long and the normal cartridge overall length of 93.5 mm has to be exceeded. The common 1:10 inch rifling twist rate also has to be tightened to stabilize very long projectiles. Such commercially non-existent cartridges are termed "wildcats". The use of a wildcat .338 Lapua Magnum based cartridge demands the use of a custom or customized rifle with an appropriately cut chamber and a fast-twist bore. An example of such a special .338 calibre extreme range bullet is the German CNC manufactured mono-metal 18.92 gram (292 gr) LM-105 (G1 BC ≈ 1.133 – this Ballistic coefficient (BC) is calculated by its designer, Mr. Lutz Möller, and not proven by Doppler radar measurements). If Mr. Möller's assumptions are right the LM-105 would have a supersonic range of ≈ 2385 m (2610 yd) at a muzzle velocity of 915 m/s (3002 ft/s) under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m³). The LM-105 bullet has an overall length of 54.79 mm (2.157 in) and derives its exceptional low drag from a radical LD Haack or Sears-Haack profile in the bullet's nose area. Rifles chambered for this wildcat cartridge, with a cartridge overall length of 105 mm (4.13 in), and equipped with custom made 1:7 inch progressive twist rate 900 mm (35.43 in) long barrels finished first and second at several long range competitions. Its most recent win (2007) was in an international Special Forces and police sniper competition in Switzerland against rifles chambered for .308 Winchester up to .50 BMG at ranges from 100 m – 1500 m (109 yd – 1640 yd). The LM-105 bullet exhibited its very low wind drift susceptibility notably at ranges beyond 800 m (875 yd).
.338 Lapua Magnum as a parent case Edit
The .300 Lapua MagnumEdit
The commercially successful .338 Lapua Magnum cartridge has functioned as the parent case for the .300 Lapua Magnum, which is essentially a necked-down version of the .338 Lapua Magnum. The .338 cartridge case was used for this since it has the capability to operate with high chamber pressures which, combined with smaller and hence lighter bullets result in very high muzzle velocities.
The Finnish ammunition manufacturer Lapua got the .300 Lapua Magnum C.I.P. certified, so it became an officially registered and sanctioned member of the Finnish "family" of super magnum rifle cartridges. The .300 Lapua Magnum is not commercially available and currently exists only as a C.I.P. datasheet. It is however still used by a few shooters who produce the cases from .338 Lapua Magnum brass by reshaping the shoulder and neck, and handloading it with .30 calibre bullets.
The .300 Lapua Magnum has a 7.33 ml (113 grains) H2O cartridge case capacity. The exterior shape of the Lapua Magnum case was designed to promote reliable feeding and extraction in bolt-action rifles and machine guns alike, under extreme conditions.
.300 Lapua Magnum maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).
Americans would define the shoulder angle at alpha/2 ≈ 25 degrees. The common rifling twist rate for this cartridge is 240 mm (1 in 9.45 in), 4 grooves, Ø lands = 7.62 mm, Ø grooves = 7.82 mm, land width = 4.47 mm and the primer type is large rifle magnum.
According to the official C.I.P. guidelines the .300 Lapua Magnum case can handle up to 470 MPa (68,167 psi) piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers.
This for rifles very high maximum allowed chamber pressure level indicates that the cases of the .300 and .338 Lapua Magnum are built extremely sturdy to cope with this for rifles very high operating pressure. The large boltface combined with the high 470 MPa maximum pressure makes that the .300 Lapua Magnum should only be chambered in rifles that are capable of handling such large and fierce cartridges and thus high bolt thrust safely. Chambering such powerful super magnum cartridges in rifles intended for normal magnum rifle cartridges and using 470 MPa loads can cause serious or fatal injury to the shooter and bystanders.
The .338 Lapua Magnum case is also used as the parent case for a host of modified variants that neither are officially registered with and sanctioned by C.I.P. nor its American equivalent, SAAMI. Such cartridges which use commercial factory cases are generally known as wildcats. By blowing out standard factory cases the wildcatter generally hopes to gain extra muzzle velocity by increasing the case capacity of the factory parent cartridge case by a few percent. Practically there can be some muzzle velocity gained by this method, but the measured results between parent cartridges and their 'improved' wildcat offspring are often marginal. Besides changing the shape and internal volume of the parent cartridge case, wildcatters also can change the original calibre. A reason to change the original calibre can be to comply with a minimal permitted calibre or bullet weight for the legal hunting of certain species of game. Because the .338 Lapua offers a large and exceptionally sturdy, pressure resistant cartridge case that can be relatively easily reloaded and hence be reused several times it has become quite popular amongst wildcatters. With the .338 Lapua Magnum as the parent case wildcatters have created 7 mm (7 mm Katzmeier), .30 (.30-338 Lapua (Triebel), .30 Wolf), 8 mm (8 mm-338 Lapua (Triebel), LM-101), .338 (.338 Yogi, LM-105), .343 (.343 Lapua Magnum LM-107), 9.3 mm (9,3-338 Lapua Magnum (Triebel)) and .375 calibre variants.
|This page uses Creative Commons Licensed content from Wikipedia (view authors).|
<ref>tags exist, but no
<references/>tag was found