Target Sports

SPORTS STARS: THE .338 LAPUA MAGNUM PART TWO

Created on 27th May 2009

Let's look at this cartridge's development, there being much information in the public domain. I previously quoted the received wisdom that it is a slightly modified and necked-down .416 Rigby, suggesting relatively simple wildcatting - actually, it wasn't! The .338 Lapua Magnum story shows the complexity of devising a new factory cartridge, especially a high-performance number.

Caveat vendor

The US Navy had commissioned RAI (Research Armament Industries) to design long-range precision anti-materiel and personnel rifles. RAI consisted of designer Jerry Haskins and former USAF officer Edward B Dillon, and they produced two rifles, the .50BMG Model 500 and .300 Win Mag Model 300, but it was apparent the latter wouldn't satisfy the sponsor's performance specifications, hence the move to .338" and an additional project to develop a new cartridge. (The USN specification stated it was to be usable in belt-fed general purpose machine-guns too!)

RAI recruited barrel-maker Boots Obermeyer and James Bell (Brass Extrusion Laboratories Limited) to undertake the cartridge design and development, the pair selecting the .416 Rigby case, or to be more precise, the BELL .416 Basic as their starting point. Bell redesigned the case-head internally for higher pressures, while Obermeyer shortened and redesigned the Rigby body shape and shoulders, so the .338/.416 was much more than a simple adaptation. Sierra Bullets declined to get involved, but Hornady was persuaded to supply a 250gn HPBTM for the project, and Obermeyer developed loads using IMR-7800 series propellants.

Things didn't work out, the oddest reason being the USN insisting on the use of faster-burning IMR-4350. This, cases that weren't robust enough, and the rifle's action not being up to the case-head thrust levels being generated, produced horrendous case attrition while muzzle velocities fell short of target. The US Army had the final decision on sponsoring further work and unsurprisingly said no. (One of the many reasons given was the bullet - only Sierra or Lapua designs were deemed acceptable!) RAI was collapsing, with Messrs Bell and Obermeyer gone, and the coup de grace was the Haskins .50-calibre Model 500 losing out to the Barratt Light-Fifty in the anti-materiel rifle stakes.

Lapua

While RAI and its .338/.416 went west, interest and, one presumes, at least some of the project data moved to the small Finnish town of Lapua, whose main employer had picked up the concept. This was courageous given the US Army had just rejected it, not to mention the contemporary widespread enthusiasm for .50 calibre cartridges.

The Finns understood that .338 viability demanded substantial ballistics performance, and that in turn required brutal pressures. The case structure was comprehensively redesigned, making it 4,000 BAR+ pressure-capable, and the body was further shortened and reshaped. As far as Lapua is concerned, the .338LM is a new design. The company is renowned for its case manufacturing quality, part of which comes from close control of brass hardness. This expertise was fully exploited in developing the .338, with a special drawing and annealing regime to produce cases that are exceptionally tough at the back end, with the brass hardness reducing in closely gradated steps to the shoulder/neck area.

Bullets, ballistics and barrels

Expanding 0.338" bullets were available in the early 1980s, but nobody made FMJ or match types. Lapua designed a 250gn FMJBT bullet for cartridge development, requirements being aerodynamic efficiency and the ability to withstand an enormous boot up the rear. This model was reputedly similar to Lapua's D-Series step-boattail designs, but the company introduced its 150gn 0.308" calibre B448 Lock-Base FMJBT match/military sniper bullet around this time and an upsized version was produced for the .338LM, designated B408. The nearly-enclosed base with a minimal area of the lead core exposed in the small ‘pimple' was regarded as ideal for the pressures. Lapua later dropped this bullet, replacing it with the GB488 version of its then-new Scenar design for improved accuracy and ballistics, the HPBTM bullet form having been ruled compliant with the Hague Convention rules by an American legal study. Both models are now offered in factory cartridges as well as handloading components.

The only other large company that offers such bullets is Sierra, with 250gn and 300gn Match Kings (SMKs), the latter having the highest BC of any Sierra design. Beyond these two, there were machined solid copper-alloy bullets from Lost River Ballistics Technologies of Arco, Idaho, and two machined mono-metal models are currently available from German Lutz Möller, his LM-105 295gn design having 0.93 BC. Cartridges loaded with this bullet have been used to win several international long-range military and sniper competitions, including a recent Swiss event covering ranges up to 1,500m, and Tom Marsti winning the prestigious Annual Lapua Sniper Competition in 2005 with a Lothar Walther barrelled Sako TRG-42. With an MV just shy of 3,000fps, a 12.5-MOA elevation increase was needed between 250m and 750m ranges. (By comparison, a typical 6.5-284 long-range F-Class load would use almost exactly 50% more.) Factory ammunition is produced by Lapua (four products - the two bullets already mentioned, plus 250gn armour-piercing and armour-piercing/incendiary versions, all around the 2,950fps mark). Other factory cartridges are from Black Hills Ammunition of Rapid City, South Dakota (250gn and 300gn Sierra MKs at 2,950 and 2,800fps respectively), and Swiss company RUAG Ammotec (250gn FMJBT military sniper).

Although the calibre has been standardised on 0.338" bullet diameter, Lapua makes them a full thousandth of an inch larger - a lot - and one assumes factory rifles have barrels dimensioned to suit. The late Malcolm Cooper was adamant that Accuracy International be partner in the development process, the AWM/AWSM rifle being an integral part of the cartridge-rifle package, but Lapua awarded it ‘cooperation partner' status alongside Sako and Mauser. Barrel accuracy life is reputedly good, the Finnish Army getting 6,000-7,000 rounds from TRG-42 tubes before groups exceed acceptable sizes - ‘acceptable' defined as 1-MOA at 1,000m! With Lapua settling on 250gn bullets most rifle-makers, including Sako with its TRG-42, have adopted a 12" rifling twist, but the 300gn SMK needs 10" and the LM-105 7.5".

Targets and handloads

The cartridge is obviously accurate - you don't hit man-sized targets at 1,500m with something that isn't - and with high-BC bullets, it seems a natural for long-range F-Class and Benchrest. One problem is location - the cartridge now banned from MoD ranges (including Bisley) apart from 12 specially-designated sites in out of the way spots such as Warcop and Kirkcudbright. I've seen claims of 0.2-MOA accuracy, but that's not borne out with factory rifles such as the TRG-42, and 0.75 to 1-MOA isn't nearly good enough these days. The ballistic advantage with 250gn bullets is not as great as you might think either. Lapua lists its Lock-Base and Scenar with BCs of 0.662 and 0.675 respectively and handloading data that gives 2,900-3,000fps (compared to the 139gn Scenar at 0.615 BC at around 3,000fps in 6.5-284). Recoil is a factor: this brutish cartridge moves the rifle a lot on the rest and bags, and that doesn't make for sub-0.5 MOA accuracy either. The TRGs that were seen a few seasons ago at Diggle have been replaced by rifles in smaller calibres. However, buy a custom gunsmith-built single-shot rifle with a long match-quality fast-twist barrel and both accuracy and ballistics are available using the 300gn SMK (0.750-.768 BC) or the Möller LM-105. Users of the latter report dramatically reduced wind-drift at 800m and above.

Nevertheless, one has to say its costs and constraints make the .338LM closer to the 50s than top F-Class cartridges such as the 7mm WSM in UK shooting. Its primary role will remain as an ultra long-range sniper cartridge, with more armies expected to adopt it in the near future.

The table below includes maximum loads! Use magnum primers and listed starting loads (but no less) and work up in small steps looking for over-pressure signs. Data applies solely to each company's or listed bullets. (C) = compressed powder charge. Note different bullet diameters depending on make (Sierra = 0.338"; Lapua = 0.339").

Sample loading data

215gn Game King 84.9 - 95.5gn Re19 3,300fps Sierra

225gn Various Max: 93.2gn Re22 3,000fps Hornady

225gn Hornady SP 82.6-90.5gn N560 3,065fps Vihtavuori

250gn Lapua B408 L-B 74.9-88.5gn N165 2,906fps Vihtavuori

250gn Lapua B448 Scenar 88.7-98.8gn (C) N570 2,989fps Vihtavuori

250gn Game King + MK 81.7-90.0gn H4831sc 3,000fps Sierra

300gn Match King 82.7-92.2gn H1000 2,750fps Sierra

300gn Sierra Match King 83.2-91.3gn N570 2,710fps Vihtavuori

SPORTS STARS: THE .338 LAPUA MAGNUM PART TWO

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SPORTS STARS: THE .338 LAPUA MAGNUM PART TWO

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