In military and law enforcement terminology, a sniper rifle is a rifle used to ensure more accurate placement of bullets at longer ranges than other small arms. A typical sniper rifle is built for optimal levels of accuracy, fitted with a telescopic sight and chambered for a military centerfirecartridge. The term is often used in the media to describe any type of accurized firearm fitted with a telescopic sight that is employed against human targets, although "sniping rifle" or "sniper's rifle" is the technically correct fashion to refer to such a rifle.
The military role of sniper (a term derived from the snipe, a bird which was difficult to hunt and shoot) dates back to the turn of the 18th century, but the true sniper rifle is a much more recent development. Advances in technology, specifically that of telescopic sights and more accurate manufacturing, allowed armies to equip specially-trained soldiers with rifles that enable them to deliver precise shots over greater distances than regular infantry weapons. The rifle itself could be based on a standard rifle (at first, a bolt-action rifle); however, when fitted with a telescopic sight, it becomes a sniper rifle.
In the American Civil War Confederate troops equipped with barrel-length three power scopes mounted on the exceptionally accurate British Whitworth rifle had been known to kill Union officers at ranges of about 800 yards (731.5m), an unheard-of distance at that time.[1][2][3][4]
The earliest sniper rifles were little more than conventional military or target rifles with long-range "peep sights" and Galilean 'open telescope' front and rear sights, designed for use on the target range. Only from the beginning of World War I did specially adapted sniper rifles come to the fore. Germany deployed military caliber hunting rifles with telescopic sights, and the British used Aldis, Winchester and Periscopic Prism Co. sights fitted by gunsmiths to regulation SMLE Mk III and Mk III* or Enfield Pattern 1914 rifles; the Canadian Ross rifle was also employed by snipers after it had been withdrawn from general issue.
Typical World War II-era sniper rifles were generally standard-issue battle rifles, selected for accuracy, with a 2.5x or 3x telescopic sight and cheek-rest fitted and the bolt turned down if necessary to allow operation with the scope fitted. Australia's No.1 Mk III* (HT) rifle was a later conversion of the SMLE fitted with the Lithgow heavy target barrel at the end of WW2. By the end of the war, forces on all sides had specially trained soldiers equipped with sniper rifles, and they have played an increasingly important role in military operations ever since.
Telescopic sight
The single most important characteristic that sets a sniper rifle apart from other military or police small arms is the mounting of a telescopic sight, which is relatively easy to distinguish from smaller optical aiming devices found on some modern assault rifles and submachine guns. This also allows the user to see farther.
The telescopic sights used on sniper rifles differ from other optical sights in that they offer much greater magnification (more than 4x and up to 40x), and have a much larger objective lens(40 to 50 mm in diameter) for a brighter image.
Most telescopic lenses employed in military or police roles have special reticles to aid with judgment of distance, which is an important factor in accurate shot placement due to the bullet's trajectory.
Cartridge
In a military setting, logistical concerns are the primary determinant of the cartridge used, so sniper rifles are usually limited to rifle cartridges commonly used by the military force employing the rifle. Since large national militaries generally change slowly, military rifle ammunition is frequently battle-tested and well-studied by ammunition and firearms experts. Consequently, police forces tend to follow military practices in choosing a sniper rifle cartridge instead of trying to break new ground with less-perfected (but possibly better) ammunition.
Before the introduction of the standard 7.62x51mm_NATO cartridge in the 1950s, standard military cartridges were the .30-06 Springfield or 7.62x63mm (United States), .303 British (7.7x56mmR) (United Kingdom) and 7.92x57mm (8mm Mauser) (Germany). The .30-06 Springfield continued in service with U.S. Marine Corps snipers during the Vietnam War in the 1970s, well after general adoption of the 7.62x51mm. At the present time, in both the Western world and within NATO, 7.62x51mm is currently the primary cartridge of choice for military and police sniper rifles.
Worldwide, the trend is similar. The preferred sniper cartridge in Russia is another .30 calibre military cartridge, the 7.62 x 54 mm R, which has similar performance to the 7.62x51mm. This cartridge was introduced in 1891, and both Russian sniper rifles of the modern era, theMosin-Nagant and the Dragunov sniper rifle, are chambered for it.
Certain commercial cartridges designed with only performance in mind, without the logistical constraints of most armies, have also gained popularity in the 1990s. These include the 7 mm Remington Magnum (7.2x64mm), .300 Winchester Magnum (7.8/7.62x67mm), and the .338 Lapua Magnum (8.6x70mm). These cartridges offer better ballistic performance and greater effective range than the 7.62x51mm. Though they are not as powerful as .50 calibre cartridges they are not as heavy as rifles chambered for .50 calibre ammunition, and are significantly more powerful than rifles chambered for 7.62x51mm.
Snipers may also employ anti-materiel rifles in sniping roles against targets such as vehicles, equipment and structures, or for the long-range destruction of explosive devices; these rifles may also be used against personnel.
Anti-materiel rifles tend to be semi-automatic and of a larger calibre than anti-personnel rifles, using cartridges such as the .50 BMG, 12.7x108mm Russian or even 14.5x114mm Russian and20mm. These large cartridges are required to be able to fire projectiles containing payloads such as explosives, armour piercing cores, incendiaries or combinations of these, such as the Raufoss Mk211 projectile. Due to the considerable size and weight of anti-materiel rifles, 2- or 3-man sniper teams become necessary.
Barrel
Barrels are normally of precise manufacture and of a heavier cross section than more traditional barrels in order to reduce the change in impact points between a first shot from a cold barrel and a follow-up shot from a warm barrel. Unlike many battle and assault rifles, the bores are usually not chromed to avoid inaccuracy due to an uneven treatment.
When installed, barrels are often free-floated, i.e., installed so the barrel only contacts the rest of the rifle at the receiver, to minimise the effects on impact point of pressure on the fore-end by slings, bipods, or the sniper's hands. The end of the barrel is usually crowned or machined to form a rebated area around the muzzle proper to avoid asymmetry or damage, and consequent inaccuracy. Alternatively, some rifles such as the Dragunov or Walther WA2000 provide structures at the fore-end to provide tension on the barrel in order to counteract barrel drop and other alterations in barrel shape.
External longitudinal fluting that contributes to heat dissipation by increasing surface area while simultaneously decreasing the weight of the barrel is sometimes used on sniper rifle barrels.
Sniper rifle barrels may also utilise a threaded muzzle or combination device (muzzle brake or flash suppressor and attachment mount) to allow the fitting of a sound suppressor. These suppressors often have means of adjusting the point of impact while fitted.
Military sniper rifles tend to have barrel lengths of 600 mm (24 inches) or longer, to allow the cartridge propellant to fully burn, reducing revealing muzzle flash and increasing bullet velocity. Police sniper rifles may use shorter barrels to improve handling characteristics. The shorter barrels' velocity loss is unimportant at closer ranges; projectile energy is more than sufficient.
Accuracy
A military-issue battle rifle or assault rifle is usually capable of between 3-6 minute of angle (MOA) (1-2 mrad) accuracy. A standard-issue military sniper rifle is typically capable of 1-3 MOA (0.3-1 mrad) accuracy, with a police sniper rifle capable of 0.25-1.5 MOA (0.1-0.5 mrad) accuracy. For comparison, a competition target or benchrest rifle may be capable of accuracy up to 0.15-0.3 MOA (0.05-0.1 mrad).
A 1 MOA (0.3 mrad) average extreme spread for a 5-shot group (meaning the center-to-center distance between the two most distant bullet holes in a shot-group) translates into 69% probability that the bullet's point of impact will be in the circle with center in point of aim and diameter of 25 cm at 800 m (about 8 inches at 800 yards), which is considered sufficient to ensure a high probability of hitting a human shape at that distance.
In 1982 a U.S. Army draft requirement for a Sniper Weapon System was: "The System will: (6) Have an accuracy of no more than 0.75 MOA (0.2 mrad) for a 5-shot group at 1,500 meters when fired from a supported, non-benchrest position".[6] Actual Sniper Weapon System (M24) adopted in 1988 has stated maximum effective range of 800 meters and a maximum allowed average mean radius (AMR) of 1.9 inches at 300 yards from a machine rest, what corresponds to a 1.6 MOA (0.5 mrad) extreme spread for a 5-shot group when using 7.62 x 51 mm M118 Special Ball cartridges.[7][8][9]
A 2008 United States military market survey for a Precision Sniper Rifle (PSR) calls for 1 MOA (0.3 mrad) extreme vertical spread for all shots in a 5-round group fired at targets at 300, 600, 900, 1,200 and 1,500 meters.[10][11] In 2009 a United States Special Operations Command market survey calls for 1 MOA (0.3 mrad) extreme vertical spread for all shots in a 10-round group fired at targets at 300, 600, 900, 1,200 and 1,500 meters.[12][13] The 2009 Precession Sniper Rifle requirements state that the PSR when fired without suppressor shall provide a confidence factor of 80% that the weapon and ammunition combination is capable of holding 1 MOA extreme vertical spread. This shall be calculated from 150 ten (10) round groups that were fired unsuppressed. No individual group shall exceed 1.5 MOA (0.5 mrad) extreme vertical spread. All accuracy will be taken at the 1,500 meter point.[14][15] In 2008 the US military adopted the M110 Semi-Automatic Sniper Systemwhich has corresponding maximum allowed extreme spread of 1.8 MOA (0.5 mrad) for a 5-shot group on 300 feet, using M118LR ammunition or equivalent.[7][8][16] In 2010 maximum bullet dispersion requirement for M24 .300 Winchester Magnumcorresponds[7][8] 1.4 MOA extreme spread for 5 shot group on 100 meters [17].
Although accuracy standards for police rifles do not widely exist, rifles are frequently seen with accuracy levels from 0.5-1.5 MOA (0.2-0.5 mrad)[18]. For typical policing situations an extreme spread accuracy level no better than 1 MOA (0.3 mrad) is usually all that is required. This is because police typically employ their rifles at short ranges.[19] At 100 m or less, a rifle with a relatively low accuracy of only 1 MOA (0.3 mrad) should be able to repeatedly hit a 3 cm (1.2 inch) target. A 3 cm diameter target is smaller than the brain stem which is targeted by police snipers for its quick killing effect.[20]
[edit]Maximum effective range
| Cartridge | Maximum effective range[21][22] |
|---|---|
| 7.62x39mm | 350 m |
| 5.56x45mm | 550 m |
| 7.62x51mm (.308 Winchester) | 800 m |
| 7.62x54mm R | 800 m |
| .30-06 Springfield | 800 m |
| 7 mm Remington Magnum | 900–1,100 m |
| .300 Winchester Magnum | 900–1,200 m |
| .338 Lapua Magnum | 1,200-1,500 m |
| .50 BMG (12.7x99mm NATO) 12.7x108mm (Russian) | 1,500–2,000 m |
| 14.5x114mm | 1,800–2,300 m |
| .408 Chey Tac | 2,300 m |
Unlike police sniper rifles, military sniper rifles tend to be employed at the greatest possible distances so that range advantages like the increased difficulty to spot and engage the sniper can be exploited. The most popular military sniper rifles (in terms of numbers in service) are chambered for 7.62 mm (0.30 inch) caliber ammunition, such as7.62x51mm and 7.62x54mm R. Since sniper rifles of this class must compete with several other types of military weapons with similar range, snipers invariably must employ skilled fieldcraft to conceal their position.
The recent trend in specialised military sniper rifles is towards larger calibres that offer relatively favorable hit probabilities at greater range, such as the anti-personnel .338 Lapua Magnum cartridge and anti-materiel cartridges like the .50 BMG and the 14.5x114mm. This allows snipers to take fewer risks, and spend less time finding concealment when facing enemies that are not equipped with similar weapons.
Maximum range claims made by military organizations and materiel manufacturers regarding sniper weapon systems are not based on consistent or strictly scientific criteria. The problem is only the bullet interacts after a relatively long flight path with the target (can also be a materiel target for a sniper bullet). This implies that variables such as the minimal required hit probability, local atmospheric conditions, properties and velocity of the employed bullet (parts), properties of the target and the desired terminal effect are major relevant factors that determine the maximum effective range of the employed system.
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