The Accuracy International AWM (Arctic Warfare Magnum) is a bolt-action sniper rifle manufactured by Accuracy International designed for magnum rifle cartridge chamberings.

The Accuracy International AWM is also unofficially known as the AWSM (Arctic Warfare Super Magnum), which typically denotes AWM rifles chambered in .338 Lapua Magnum.On 25 September 2012 Accuracy International announced on their company website that the AWM .338 Lapua Magnum rifle is being phased out and replaced by the Accuracy International AX338 rifle.

Arctic Warfare Magnum system

The Accuracy International AWM rifle is a variant of the British Accuracy International Arctic Warfare (AW) rifle that was the basis of a family of sniper rifles using the Arctic Warfare name. As such the design details of the AWM variant are similar to the ones found in the basic AW rifle system. Compared to the AW, the AWM has a longer bolt to accommodate dimensionally larger magnum-length cartridges such as the .300 Winchester Magnum and the .338 Lapua Magnum. The bolt head, locking ring, and extractor and magazines were also revised to work with the increased size and operating pressures of magnum rifle cartridges.

The AWM features a detachable single stack removable box magazine which holds five rounds. The normal cartridges for this rifle, and the ones which have been accepted by NATO for use in AWM rifles, are .300 Winchester Magnum and .338 Lapua Magnum.

Muzzle brakes are fitted to reduce recoil, jump and flash and act as a base for optional iron sights and suppressors.
Normally, the AWMs are outfitted with a Schmidt & Bender PM II 10×42/MILITARY MK II 10×42 telescopic sight with 10× fixed power of magnification. However, a Schmidt & Bender PM II/MILITARY MK II with variable magnification of either 3–12×50, 4–16×50 or 5–25×56 can be used if the operator wants more flexibility to shoot at varying ranges, or when a wide field of view is required.

Accuracy International actively promotes fitting the German made Schmidt & Bender PM II/MILITARY MK II product line as sighting components on their rifles, which is rare for a rifle manufacturer. The German and Russian Army preferred a telescopic sight made by Zeiss[2] over Accuracy International’s preference.

The AWM rifle is normally supplied in a metal transit case together with a telescopic sight, mount, butt spacers, bipod, spare magazines, sling, cleaning and tool kits.

Magnum chamberings

.300 Winchester Magnum
The .300 Winchester Magnum (7.62×67mm) cartridge was designed as a magnum hunting cartridge and offers a flatter trajectory and a significant increase in muzzle velocity, wind resistance and supersonic range over the dimensionally smaller 7.62×51mm NATO cartridge. The ability of the .300 Winchester Magnum chambering to obtain fairly high muzzle velocities combined with their diameter or caliber relatively heavy and long very-low-drag bullets significantly enhance the hit probability at longer ranges and hence the effective range compared to the 7.62×51mm NATO cartridge. For precision shooting, the Federal Gold Medal Match grade is the most commonly used ammunition.[citation needed]
The AWM chambered for the .300 Winchester Magnum is fitted with a fluted, stainless steel barrel that is 660 mm (26″) long for optimum muzzle velocity and nominal weight. The .300 Winchester Magnum barrel features a non-traditional 279.4 mm (1:11 in) right-hand twist rate.

.338 Lapua Magnum

The AWM in the .338 Lapua Magnum (8.6×70mm) calibre was designed as a dedicated long range sniper rifle combining the maneuverability of rifles chambered in 7.62×51mm NATO with the greater power and range of the .50 BMG cartridge.
Compared to most .50 calibre rifles, the AWM offers considerably less rifle weight, recoil, muzzle flash, smoke and report.[citation needed] Although the .338 Lapua Magnum delivers less kinetic energy to the target compared with the .50 BMG, both cartridges have similar trajectories, resistance to wind drift and penetration, while the .338 Lapua Magnum unquestionably outperforms the 7.62×51mm NATO and .300 Winchester Magnum, especially at ranges beyond 800 metres (875 yd) and 1,100 metres (1,203 yd). AWM rifles in .338 Lapua Magnum can also be deployed against unarmoured hard targets, including armoured glass.

The AWM .338 Lapua Magnum is fitted with a stainless steel, fluted, 686 mm (27″) barrel, which research has found to be the best compromise between muzzle velocity on the one hand, and weight and length on the other. The rifle’s barrel has an unconventional 279 mm (1:11 in) right-hand twist rate, optimized for firing .338-calibre very-low-drag bullets up to 16.85 g (260 gr). When the AWM .338 Lapua Magnum was developed military issue cartridges were loaded with 16.2 g (250 gr) very-low-drag bullets. Longer, heavier very-low-drag bullets like the Sierra HPBT MatchKing .338-calibre 19.44 g (300 gr) and the 21st century 19.44 gram (300 grain) .338-calibre HPBT Scenar can be used, but require a 254 mm (1:10 in) twist rate to stabilize them under high air density conditions as found on arctic coasts.

A limitation of AWM rifles is that .338 Lapua Magnum cartridges loaded to the Commission Internationale Permanente pour l’Epreuve des Armes à Feu Portatives (C.I.P.) maximum allowed overall length of 93.50 mm (3.681 in) do not fit in the magazine due to a lack of internal magazine length. The reason for this limitation is that the AWM bolt action was initially developed for dimensionally smaller cartridges and then modified for the .338 Lapua Magnum chambering. Ammunition manufacturers produce .338 Lapua Magnum military issue cartridges loaded with 16.2 g (250 gr) very-low-drag bullets (overall length ≤ 91.44 mm / 3.600 in) that fit in the 91.50 mm (3.602 in) long AWM magazines. As long as .338 Lapua Magnum cartridges that fit in the magazines are used, the AWM rifles can be used as repeating rifles instead of single shot rifles.

To address .338 Lapua Magnum ammunition length limitations of the AWM Accuracy International has since developed the AX338 long range rifle as the AWM successor model. Compared to the AWM, the bolt action of the AX338 is longer and wider and the internal magazine is lengthened, allowing the unimpaired use of .338 Lapua Magnum cartridges loaded to the C.I.P. (Permanent International Commission for the Proof of Firearms Portable) maximum allowed overall length of 93.50 mm (3.681 in). Further the AX338 has a 238 mm (1:9.375 in) twist rate to adequately stabilize longer, heavier .338 caliber very-low-drag projectile designs that became more common in the 21st century.
Ammunition types currently available for the .338 Lapua Magnum are FMJ, hollow point, Armor Piercing (AP) and Armor Piercing Incendiary (API).

Longest confirmed sniper kill

In November 2009, British Army sniper Corporal of Horse (CoH) Craig Harrison, a member of the Household Cavalry, set the current record for longest recorded sniper kill by killing two Taliban machine gunners consecutively south of Musa Qala in Helmand Province in Afghanistan at a range of 2,475 m (2,707 yd) taking 10 shots to hit the target, using a L115A3 Long Range Rifle. In the reports CoH Harrison mentions the environmental conditions were perfect for long range shooting: no wind, mild weather, clear visibility

Ballistics and use of environment and equipment to achieve the aiming solution

According to JBM Ballistics, using drag coefficients (Cd) provided by Lapua, the L115A3 has an approximate supersonic range (speed of sound = 340.3 m/s) of 1,375 m (1,504 yd) under International Standard Atmosphere conditions at sea level (air density ρ = 1.225 kg/m3) and 1,548 m (1,693 yd) at the 1,043 m (3,422 ft) altitude or elevation (air density ρ = 1.1069 kg/m3) of Musa Qala. This illustrates how differences in environmental conditions can significantly affect bullet flight.

The Schmidt & Bender MILITARY MKII 5-25×56 0.1 MIL RAD parallax, illumination, double turn telescopic sight used by Harrison on the L115A3 Long Range Rifle can be adjusted in 0.1 milliradian or mil increments (at a distance of 2,475 m (2,707 yd) 1 adjustment increment of 0.1 milliradian equates to a 24.75 cm (9.74 in) point of impact shift) and has a maximal vertical elevation range of 26 milliradian. To increase the maximal elevation range Accuracy International produces mounts for telescopic sights with a 13.09 mil (45 MOA) built in vertical cant designed for their .338 Lapua Magnum rifles fitted with the 5-25×56 telescopic sight. Even with a 13.09 mil canted mount the employed sighting system is not able to dial in over 39.09 milliradian of vertical aiming correction, which is significantly less than Harrison required during his record shot.

The external ballistics software program by JBM Ballistics predicts that the bullets of British high pressure .338 Lapua Magnum cartridges using 16.2 g (250 gr) Lapua LockBase B408 bullets fired at 936 m/s (3,071 ft/s) muzzle velocity under International Standard Atmosphere conditions at 1,043 m (3,422 ft) elevation (air density ρ = 1.1069 kg/m3) and assuming a flat fire scenario (a situation where the shooting and target positions are at equal elevation) and a 100 m (109 yd) zero (the distance at which the rifle is sighted in) arrive at 2,475 m (2,707 yd) distance after approximately 6.017 seconds flight time at 251.8 m/s (826 ft/s) velocity and have dropped 120.95 m (396.8 ft) or in angular units 48.9 milliradian (168 MOA) on their way. Harrison had to use the P4 reticle offering 0.5 mil spaced holdover hash marks in his 5-25×56 telescopic sight to compensate for the lack of vertical aiming correction and thus achieve the required aiming solution. The long horizontal line at 5× zoom or magnification represent 49.09 milliradian (168.6 MOA) or slightly over the required assumed vertical elevation