In military and law enforcement terminology, a sniper rifle is a precision-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 centerfire cartridge. 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 a 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III and Mk III* or Enfield Pattern 1914 rifles; the Canadian Ross rifle was also employed by snipers after it had been withdrawn from general issue.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.
Military
Sniper rifles aimed at military service are often designed for very high durability, range, reliability, sturdiness, serviceability and repairability under adverse environmental and combat conditions, at the sacrifice of a small degree of accuracy. Military snipers and sharpshooters may also be required to carry their rifles and other equipment for long distances, making it important to minimize weight. Military organizations often operate under strict budget constraints, which influences the type and quality of sniper rifles they purchase.
Law Enforcement
Sniper rifles built or modified for use in law enforcement are generally required to have the greatest possible accuracy, more than military rifles, but do not need to have as long a range.
As law enforcement-specific rifles are usually used in non-combat (often urban) environments, they do not have the requirement to be as hardy or portable as military versions; nevertheless they may be smaller, as they do not need very long range.
Some of the first sniper rifles designed specifically to meet police and other law-enforcement requirements were developed for West German police after the Munich massacre at the 1972 Summer Olympics. Many police services and law enforcement organizations (such as the U.S. Secret Service) now use rifles designed for law enforcement purposes.
The Heckler & Koch PSG1 is one rifle specifically designed to meet these criteria and is often referred to as an ideal example of this type of sniper rifle. The FN Special Police Rifle was built for and is marketed to law enforcement rather than military agencies.
Scope 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.
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 a 69% probability that the bullet's point of impact will be in a target circle with a diameter of 23.3 cm at 800 m (about 8 inches at 800 yards). This average extreme spread for a 5-shot group and the accompanying hit probability are considered sufficient for effectively hitting a human shape at 800 m 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 0.6 MOA (0.5 mrad) extreme spread for a 5-shot group when using 7.62 x 51 mm M118 Special Ball cartridges.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 System which 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 Magnum corresponds[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]
Max Effective Range
The listed maximum ranges of commonly used military and police sniping cartridges are mainly consistent with the claims made by military organizations and materiel manufacturers, but not based on consistent or strictly scientific criteria. The problem is only the bullet interacts with the target (can also be a materiel target for a sniper bullet). This implies that the properties of the target, properties and velocity of the employed bullet (parts) and desired effect are the most relevant factors.
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 as 7.62x51mm 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 specialized military sniper rifles is towards larger calibers 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.
